C++: Share TInstruction across IR stages

Each stage of the IR reuses the majority of the instructions from previous stages. Previously, we've been wrapping each reused old instruction in a branch of the `TInstruction` type for the next stage. This causes use to create roughly three times as many `TInstruction` objects as we actually need.

Now that IPA union types are supported in the compiler, we can share a single `TInstruction` IPA type across stages. We create a single `TInstruction` IPA type, with individual branches of this type for instructions created directly from the AST (`TRawInstruction`) and for instructions added by each stage of SSA construction (`T*PhiInstruction`, `T*ChiInstruction`, `T*UnreachedInstruction`). Each stage then defines a `TStageInstruction` type that is a union of all of the branches that can appear in that particular stage. The public `Instruction` class for each phase extends the `TStageInstruction` type for that stage.

The interface that each stage exposes to the pyrameterized modules in the IR is now split into three pieces:
- The `Raw` module, exposed only by the original IR construction stage. This module identifies which functions have IR, which `TRawInstruction`s exist, and which `IRVariable`s exist.
- The `SSA` module, exposed only by the two SSA construction stages. This identifiers which `Phi`, `Chi`, and `Unreached` instructions exist.
- The global module, exposed by all three stages. This module has all of the predicates whose implementation is different for each stage, like gathering definitions of `MemoryOperand`s.

Similarly, there is now a single `TIRFunction` IPA type that is shared across all three stages. There is a single `IRFunctionBase` class that exposes the stage-indepdendent predicates; the `IRFunction` class for each stage extends `IRFunctionBase`.

Most of the other changes are largely mechanical.

config/identical-files.json

@@ -177,6 +177,11 @@
     "cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/IRBlockImports.qll",
     "cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/IRBlockImports.qll"
   ],
+  "C++ IR IRFunctionImports": [
+    "cpp/ql/src/semmle/code/cpp/ir/implementation/raw/internal/IRFunctionImports.qll",
+    "cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/IRFunctionImports.qll",
+    "cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/IRFunctionImports.qll"
+  ],
   "C++ IR IRVariableImports": [
     "cpp/ql/src/semmle/code/cpp/ir/implementation/raw/internal/IRVariableImports.qll",
     "cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/IRVariableImports.qll",

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/IRFunction.qll

@@ -1,29 +1,12 @@
 private import internal.IRInternal
+private import internal.IRFunctionImports as Imports
+import Imports::IRFunctionBase
 import Instruction
 
-private newtype TIRFunction =
-  MkIRFunction(Language::Function func) { Construction::functionHasIR(func) }
-
 /**
- * Represents the IR for a function.
+ * The IR for a function.
  */
-class IRFunction extends TIRFunction {
+class IRFunction extends IRFunctionBase {
-  Language::Function func;
-
-  IRFunction() { this = MkIRFunction(func) }
-
-  final string toString() { result = "IR: " + func.toString() }
-
-  /**
-   * Gets the function whose IR is represented.
-   */
-  final Language::Function getFunction() { result = func }
-
-  /**
-   * Gets the location of the function.
-   */
-  final Language::Location getLocation() { result = func.getLocation() }
-
   /**
    * Gets the entry point for this function.
    */

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/Instruction.qll

@@ -29,7 +29,13 @@ private Instruction getAnInstructionAtLine(IRFunction irFunc, Language::File fil
 /**
  * Represents a single operation in the IR.
  */
-class Instruction extends Construction::TInstruction {
+class Instruction extends Construction::TStageInstruction {
+  Instruction() {
+    // The base `TStageInstruction` type is a superset of the actual instructions appearing in this
+    // stage. This call lets the stage filter out the ones that are not reused from raw IR.
+    Construction::hasInstruction(this)
+  }
+
   final string toString() { result = getOpcode().toString() + ": " + getAST().toString() }
 
   /**
@@ -250,7 +256,7 @@ class Instruction extends Construction::TInstruction {
    * result of the `Load` instruction is a prvalue of type `int`, representing
    * the integer value loaded from variable `x`.
    */
-  final predicate isGLValue() { Construction::getInstructionResultType(this).hasType(_, true) }
+  final predicate isGLValue() { getResultLanguageType().hasType(_, true) }
 
   /**
    * Gets the size of the result produced by this instruction, in bytes. If the
@@ -259,7 +265,7 @@ class Instruction extends Construction::TInstruction {
    * If `this.isGLValue()` holds for this instruction, the value of
    * `getResultSize()` will always be the size of a pointer.
    */
-  final int getResultSize() { result = Construction::getInstructionResultType(this).getByteSize() }
+  final int getResultSize() { result = getResultLanguageType().getByteSize() }
 
   /**
    * Gets the opcode that specifies the operation performed by this instruction.

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/IRFunctionImports.qll

@@ -0,0 +1 @@
+import semmle.code.cpp.ir.implementation.internal.IRFunctionBase as IRFunctionBase

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/SSAConstruction.qll

@@ -1,5 +1,11 @@
 import SSAConstructionInternal
-private import SSAConstructionImports
+private import SSAConstructionImports as Imports
+private import Imports::Opcode
+private import Imports::OperandTag
+private import Imports::Overlap
+private import Imports::TInstruction
+private import Imports::RawIR as RawIR
+private import SSAInstructions
 private import NewIR
 
 private class OldBlock = Reachability::ReachableBlock;
@@ -10,54 +16,35 @@ import Cached
 
 cached
 private module Cached {
+  class TStageInstruction =
+    TRawInstruction or TPhiInstruction or TChiInstruction or TUnreachedInstruction;
+
+  private TRawInstruction rawInstruction(
+    IRFunctionBase irFunc, Opcode opcode, Language::AST ast, Language::LanguageType resultType
+  ) {
+    result = TRawInstruction(irFunc, opcode, ast, resultType, _, _) and
+    result instanceof OldInstruction
+  }
+
+  cached
+  predicate hasInstruction(TStageInstruction instr) {
+    instr instanceof TRawInstruction and instr instanceof OldInstruction
+    or
+    not instr instanceof TRawInstruction
+  }
+
   private IRBlock getNewBlock(OldBlock oldBlock) {
     result.getFirstInstruction() = getNewInstruction(oldBlock.getFirstInstruction())
   }
 
   cached
-  predicate functionHasIR(Language::Function func) {
+  OldInstruction getOldInstruction(Instruction instr) { instr = result }
-    exists(OldIR::IRFunction irFunc | irFunc.getFunction() = func)
-  }
-
-  cached
-  OldInstruction getOldInstruction(Instruction instr) { instr = WrappedInstruction(result) }
 
   private IRVariable getNewIRVariable(OldIR::IRVariable var) {
     // This is just a type cast. Both classes derive from the same newtype.
     result = var
   }
 
-  cached
-  newtype TInstruction =
-    WrappedInstruction(OldInstruction oldInstruction) {
-      not oldInstruction instanceof OldIR::PhiInstruction
-    } or
-    Phi(OldBlock block, Alias::MemoryLocation defLocation) {
-      definitionHasPhiNode(defLocation, block)
-    } or
-    Chi(OldInstruction oldInstruction) {
-      not oldInstruction instanceof OldIR::PhiInstruction and
-      hasChiNode(_, oldInstruction)
-    } or
-    Unreached(Language::Function function) {
-      exists(OldInstruction oldInstruction |
-        function = oldInstruction.getEnclosingFunction() and
-        Reachability::isInfeasibleInstructionSuccessor(oldInstruction, _)
-      )
-    }
-
-  cached
-  predicate hasTempVariable(
-    Language::Function func, Language::AST ast, TempVariableTag tag, Language::LanguageType type
-  ) {
-    exists(OldIR::IRTempVariable var |
-      var.getEnclosingFunction() = func and
-      var.getAST() = ast and
-      var.getTag() = tag and
-      var.getLanguageType() = type
-    )
-  }
-
   cached
   predicate hasModeledMemoryResult(Instruction instruction) {
     exists(Alias::getResultMemoryLocation(getOldInstruction(instruction))) or
@@ -73,7 +60,7 @@ private module Cached {
     or
     // Chi instructions track virtual variables, and therefore a chi instruction is
     // conflated if it's associated with the aliased virtual variable.
-    exists(OldInstruction oldInstruction | instruction = Chi(oldInstruction) |
+    exists(OldInstruction oldInstruction | instruction = getChi(oldInstruction) |
       Alias::getResultMemoryLocation(oldInstruction).getVirtualVariable() instanceof
         Alias::AliasedVirtualVariable
     )
@@ -81,7 +68,7 @@ private module Cached {
     // Phi instructions track locations, and therefore a phi instruction is
     // conflated if it's associated with a conflated location.
     exists(Alias::MemoryLocation location |
-      instruction = Phi(_, location) and
+      instruction = getPhi(_, location) and
       not exists(location.getAllocation())
     )
   }
@@ -128,7 +115,7 @@ private module Cached {
       hasMemoryOperandDefinition(oldInstruction, oldOperand, overlap, result)
     )
     or
-    instruction = Chi(getOldInstruction(result)) and
+    instruction = getChi(getOldInstruction(result)) and
     tag instanceof ChiPartialOperandTag and
     overlap instanceof MustExactlyOverlap
     or
@@ -172,13 +159,15 @@ private module Cached {
 
   pragma[noopt]
   cached
-  Instruction getPhiOperandDefinition(Phi instr, IRBlock newPredecessorBlock, Overlap overlap) {
+  Instruction getPhiOperandDefinition(
+    PhiInstruction instr, IRBlock newPredecessorBlock, Overlap overlap
+  ) {
     exists(
       Alias::MemoryLocation defLocation, Alias::MemoryLocation useLocation, OldBlock phiBlock,
       OldBlock predBlock, OldBlock defBlock, int defOffset, Alias::MemoryLocation actualDefLocation
     |
       hasPhiOperandDefinition(defLocation, useLocation, phiBlock, predBlock, defBlock, defOffset) and
-      instr = Phi(phiBlock, useLocation) and
+      instr = getPhi(phiBlock, useLocation) and
       newPredecessorBlock = getNewBlock(predBlock) and
       result = getDefinitionOrChiInstruction(defBlock, defOffset, defLocation, actualDefLocation) and
       overlap = Alias::getOverlap(actualDefLocation, useLocation)
@@ -191,7 +180,7 @@ private module Cached {
       Alias::VirtualVariable vvar, OldInstruction oldInstr, Alias::MemoryLocation defLocation,
       OldBlock defBlock, int defRank, int defOffset, OldBlock useBlock, int useRank
     |
-      chiInstr = Chi(oldInstr) and
+      chiInstr = getChi(oldInstr) and
       vvar = Alias::getResultMemoryLocation(oldInstr).getVirtualVariable() and
       hasDefinitionAtRank(vvar, defLocation, defBlock, defRank, defOffset) and
       hasUseAtRank(vvar, useBlock, useRank, oldInstr) and
@@ -203,7 +192,7 @@ private module Cached {
   cached
   Instruction getPhiInstructionBlockStart(PhiInstruction instr) {
     exists(OldBlock oldBlock |
-      instr = Phi(oldBlock, _) and
+      instr = getPhi(oldBlock, _) and
       result = getNewInstruction(oldBlock.getFirstInstruction())
     )
   }
@@ -228,20 +217,20 @@ private module Cached {
   Instruction getInstructionSuccessor(Instruction instruction, EdgeKind kind) {
     if hasChiNode(_, getOldInstruction(instruction))
     then
-      result = Chi(getOldInstruction(instruction)) and
+      result = getChi(getOldInstruction(instruction)) and
       kind instanceof GotoEdge
     else (
       exists(OldInstruction oldInstruction |
         oldInstruction = getOldInstruction(instruction) and
         (
           if Reachability::isInfeasibleInstructionSuccessor(oldInstruction, kind)
-          then result = Unreached(instruction.getEnclosingFunction())
+          then result = unreachedInstruction(instruction.getEnclosingIRFunction())
           else result = getNewInstruction(oldInstruction.getSuccessor(kind))
         )
       )
       or
       exists(OldInstruction oldInstruction |
-        instruction = Chi(oldInstruction) and
+        instruction = getChi(oldInstruction) and
         result = getNewInstruction(oldInstruction.getSuccessor(kind))
       )
     )
@@ -260,84 +249,61 @@ private module Cached {
       // `oldInstruction`, in which case the back edge should come out of the
       // chi node instead.
       if hasChiNode(_, oldInstruction)
-      then instruction = Chi(oldInstruction)
+      then instruction = getChi(oldInstruction)
       else instruction = getNewInstruction(oldInstruction)
     )
   }
 
   cached
-  Language::AST getInstructionAST(Instruction instruction) {
+  Language::AST getInstructionAST(TStageInstruction instr) {
-    exists(OldInstruction oldInstruction |
+    instr = rawInstruction(_, _, result, _)
-      instruction = WrappedInstruction(oldInstruction)
+    or
-      or
+    exists(RawIR::Instruction blockStartInstr |
-      instruction = Chi(oldInstruction)
+      instr = phiInstruction(_, _, blockStartInstr, _) and
-    |
+      result = blockStartInstr.getAST()
-      result = oldInstruction.getAST()
     )
     or
-    exists(OldBlock block |
+    exists(RawIR::Instruction primaryInstr |
-      instruction = Phi(block, _) and
+      instr = chiInstruction(_, _, primaryInstr) and
-      result = block.getFirstInstruction().getAST()
+      result = primaryInstr.getAST()
     )
     or
-    instruction = Unreached(result)
+    exists(IRFunctionBase irFunc |
+      instr = unreachedInstruction(irFunc) and result = irFunc.getFunction()
+    )
   }
 
   cached
-  Language::LanguageType getInstructionResultType(Instruction instruction) {
+  Language::LanguageType getInstructionResultType(TStageInstruction instr) {
-    exists(OldInstruction oldInstruction |
+    instr = rawInstruction(_, _, _, result)
-      instruction = WrappedInstruction(oldInstruction) and
-      result = oldInstruction.getResultLanguageType()
-    )
     or
-    exists(OldInstruction oldInstruction, Alias::VirtualVariable vvar |
+    instr = phiInstruction(_, result, _, _)
-      instruction = Chi(oldInstruction) and
-      hasChiNode(vvar, oldInstruction) and
-      result = vvar.getType()
-    )
     or
-    exists(Alias::MemoryLocation location |
+    instr = chiInstruction(_, result, _)
-      instruction = Phi(_, location) and
-      result = location.getType()
-    )
     or
-    instruction = Unreached(_) and
+    instr = unreachedInstruction(_) and result = Language::getVoidType()
-    result = Language::getVoidType()
   }
 
   cached
-  Opcode getInstructionOpcode(Instruction instruction) {
+  Opcode getInstructionOpcode(TStageInstruction instr) {
-    exists(OldInstruction oldInstruction |
+    instr = rawInstruction(_, result, _, _)
-      instruction = WrappedInstruction(oldInstruction) and
-      result = oldInstruction.getOpcode()
-    )
     or
-    instruction instanceof Chi and
+    instr = phiInstruction(_, _, _, _) and result instanceof Opcode::Phi
-    result instanceof Opcode::Chi
     or
-    instruction instanceof Phi and
+    instr = chiInstruction(_, _, _) and result instanceof Opcode::Chi
-    result instanceof Opcode::Phi
     or
-    instruction instanceof Unreached and
+    instr = unreachedInstruction(_) and result instanceof Opcode::Unreached
-    result instanceof Opcode::Unreached
   }
 
   cached
-  IRFunction getInstructionEnclosingIRFunction(Instruction instruction) {
+  IRFunctionBase getInstructionEnclosingIRFunction(TStageInstruction instr) {
-    exists(OldInstruction oldInstruction |
+    instr = rawInstruction(result, _, _, _)
-      instruction = WrappedInstruction(oldInstruction)
-      or
-      instruction = Chi(oldInstruction)
-    |
-      result.getFunction() = oldInstruction.getEnclosingFunction()
-    )
     or
-    exists(OldBlock block |
+    instr = phiInstruction(result, _, _, _)
-      instruction = Phi(block, _) and
-      result.getFunction() = block.getEnclosingFunction()
-    )
     or
-    instruction = Unreached(result.getFunction())
+    instr = chiInstruction(result, _, _)
+    or
+    instr = unreachedInstruction(result)
   }
 
   cached
@@ -401,7 +367,7 @@ private module Cached {
     )
     or
     exists(OldIR::Instruction oldInstruction |
-      instruction = Chi(oldInstruction) and
+      instruction = getChi(oldInstruction) and
       result = getNewInstruction(oldInstruction)
     )
   }
@@ -409,6 +375,14 @@ private module Cached {
 
 private Instruction getNewInstruction(OldInstruction instr) { getOldInstruction(result) = instr }
 
+private ChiInstruction getChi(OldInstruction primaryInstr) {
+  result = chiInstruction(_, _, primaryInstr)
+}
+
+private PhiInstruction getPhi(OldBlock defBlock, Alias::MemoryLocation defLocation) {
+  result = phiInstruction(_, _, defBlock.getFirstInstruction(), defLocation)
+}
+
 /**
  * Holds if instruction `def` needs to have a `Chi` instruction inserted after it, to account for a partial definition
  * of a virtual variable. The `Chi` instruction provides a definition of the entire virtual variable of which the
@@ -588,7 +562,7 @@ module DefUse {
     |
       // An odd offset corresponds to the `Chi` instruction.
       defOffset = oldOffset * 2 + 1 and
-      result = Chi(oldInstr) and
+      result = getChi(oldInstr) and
       (
         defLocation = Alias::getResultMemoryLocation(oldInstr) or
         defLocation = Alias::getResultMemoryLocation(oldInstr).getVirtualVariable()
@@ -607,7 +581,7 @@ module DefUse {
     or
     defOffset = -1 and
     hasDefinition(_, defLocation, defBlock, defOffset) and
-    result = Phi(defBlock, defLocation) and
+    result = getPhi(defBlock, defLocation) and
     actualDefLocation = defLocation
   }
 
@@ -891,7 +865,7 @@ private module CachedForDebugging {
     )
     or
     exists(Alias::MemoryLocation location, OldBlock phiBlock, string specificity |
-      instr = Phi(phiBlock, location) and
+      instr = getPhi(phiBlock, location) and
       result =
         "Phi Block(" + phiBlock.getUniqueId() + ")[" + specificity + "]: " + location.getUniqueId() and
       if location instanceof Alias::VirtualVariable
@@ -901,7 +875,7 @@ private module CachedForDebugging {
       else specificity = "s"
     )
     or
-    instr = Unreached(_) and
+    instr = unreachedInstruction(_) and
     result = "Unreached"
   }
 
@@ -961,3 +935,44 @@ module SSAConsistency {
     )
   }
 }
+
+/**
+ * Provides the portion of the parameterized IR interface that is used to construct the SSA stages
+ * of the IR. The raw stage of the IR does not expose these predicates.
+ */
+cached
+module SSA {
+  class MemoryLocation = Alias::MemoryLocation;
+
+  cached
+  predicate hasPhiInstruction(
+    IRFunction irFunc, Language::LanguageType resultType, OldInstruction blockStartInstr,
+    Alias::MemoryLocation defLocation
+  ) {
+    exists(OldBlock oldBlock |
+      definitionHasPhiNode(defLocation, oldBlock) and
+      irFunc = oldBlock.getEnclosingIRFunction() and
+      blockStartInstr = oldBlock.getFirstInstruction() and
+      resultType = defLocation.getType()
+    )
+  }
+
+  cached
+  predicate hasChiInstruction(
+    IRFunctionBase irFunc, Language::LanguageType resultType, OldInstruction primaryInstruction
+  ) {
+    exists(Alias::VirtualVariable vvar |
+      hasChiNode(vvar, primaryInstruction) and
+      irFunc = primaryInstruction.getEnclosingIRFunction() and
+      resultType = vvar.getType()
+    )
+  }
+
+  cached
+  predicate hasUnreachedInstruction(IRFunction irFunc) {
+    exists(OldInstruction oldInstruction |
+      irFunc = oldInstruction.getEnclosingIRFunction() and
+      Reachability::isInfeasibleInstructionSuccessor(oldInstruction, _)
+    )
+  }
+}

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/SSAConstructionImports.qll

@@ -1,3 +1,5 @@
-import semmle.code.cpp.ir.implementation.Opcode
+import semmle.code.cpp.ir.implementation.Opcode as Opcode
-import semmle.code.cpp.ir.implementation.internal.OperandTag
+import semmle.code.cpp.ir.implementation.internal.OperandTag as OperandTag
-import semmle.code.cpp.ir.internal.Overlap
+import semmle.code.cpp.ir.internal.Overlap as Overlap
+import semmle.code.cpp.ir.implementation.internal.TInstruction as TInstruction
+import semmle.code.cpp.ir.implementation.raw.IR as RawIR

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/SSAConstructionInternal.qll

@@ -2,5 +2,6 @@ import semmle.code.cpp.ir.implementation.unaliased_ssa.IR as OldIR
 import semmle.code.cpp.ir.implementation.unaliased_ssa.internal.reachability.ReachableBlock as Reachability
 import semmle.code.cpp.ir.implementation.unaliased_ssa.internal.reachability.Dominance as Dominance
 import semmle.code.cpp.ir.implementation.aliased_ssa.IR as NewIR
+import semmle.code.cpp.ir.implementation.internal.TInstruction::AliasedSSAInstructions as SSAInstructions
 import semmle.code.cpp.ir.internal.IRCppLanguage as Language
 import AliasedSSA as Alias

cpp/ql/src/semmle/code/cpp/ir/implementation/internal/IRFunctionBase.qll

@@ -0,0 +1,23 @@
+private import IRFunctionBaseInternal
+
+private newtype TIRFunction =
+  MkIRFunction(Language::Function func) { IRConstruction::Raw::functionHasIR(func) }
+
+/**
+ * The IR for a function. This base class contains only the predicates that are the same between all
+ * phases of the IR. Each instantiation of `IRFunction` extends this class.
+ */
+class IRFunctionBase extends TIRFunction {
+  Language::Function func;
+
+  IRFunctionBase() { this = MkIRFunction(func) }
+
+  /** Gets a textual representation of this element. */
+  final string toString() { result = "IR: " + func.toString() }
+
+  /** Gets the function whose IR is represented. */
+  final Language::Function getFunction() { result = func }
+
+  /** Gets the location of the function. */
+  final Language::Location getLocation() { result = func.getLocation() }
+}

cpp/ql/src/semmle/code/cpp/ir/implementation/internal/IRFunctionBaseInternal.qll

@@ -0,0 +1,2 @@
+import semmle.code.cpp.ir.internal.IRCppLanguage as Language
+import semmle.code.cpp.ir.implementation.raw.internal.IRConstruction as IRConstruction

cpp/ql/src/semmle/code/cpp/ir/implementation/internal/TIRVariableInternal.qll

@@ -1,5 +1,5 @@
 import semmle.code.cpp.ir.internal.IRCppLanguage as Language
-import semmle.code.cpp.ir.implementation.raw.internal.IRConstruction as Construction
+import semmle.code.cpp.ir.implementation.raw.internal.IRConstruction::Raw as Construction
 private import semmle.code.cpp.ir.implementation.TempVariableTag as TempVariableTag_
 
 module Imports {

cpp/ql/src/semmle/code/cpp/ir/implementation/internal/TInstruction.qll

@@ -0,0 +1,111 @@
+private import TInstructionInternal
+private import IRFunctionBase
+private import TInstructionImports as Imports
+private import Imports::IRType
+private import Imports::Opcode
+
+/**
+ * An IR instruction. `TInstruction` is shared across all phases of the IR. There are individual
+ * branches of this type for instructions created directly from the AST (`TRawInstruction`) and for
+ * instructions added by each stage of SSA construction (`T*PhiInstruction`, `T*ChiInstruction`,
+ * `T*UnreachedInstruction`). Each stage then defines a `TStageInstruction` type that is a union of
+ * all of the branches that can appear in that particular stage. The public `Instruction` class for
+ * each phase extends the `TStageInstruction` type for that stage.
+ */
+newtype TInstruction =
+  TRawInstruction(
+    IRFunctionBase irFunc, Opcode opcode, Language::AST ast, Language::LanguageType resultType,
+    IRConstruction::Raw::InstructionTag1 tag1, IRConstruction::Raw::InstructionTag2 tag2
+  ) {
+    IRConstruction::Raw::hasInstruction(irFunc.getFunction(), opcode, ast, resultType, tag1, tag2)
+  } or
+  TUnaliasedSSAPhiInstruction(
+    IRFunctionBase irFunc, Language::LanguageType resultType, TRawInstruction blockStartInstr,
+    UnaliasedSSA::SSA::MemoryLocation memoryLocation
+  ) {
+    UnaliasedSSA::SSA::hasPhiInstruction(irFunc, resultType, blockStartInstr, memoryLocation)
+  } or
+  TUnaliasedSSAChiInstruction(
+    IRFunctionBase irFunc, Language::LanguageType resultType, TRawInstruction primaryInstruction
+  ) {
+    none()
+  } or
+  TUnaliasedSSAUnreachedInstruction(IRFunctionBase irFunc) {
+    UnaliasedSSA::SSA::hasUnreachedInstruction(irFunc)
+  } or
+  TAliasedSSAPhiInstruction(
+    IRFunctionBase irFunc, Language::LanguageType resultType, TRawInstruction blockStartInstr,
+    AliasedSSA::SSA::MemoryLocation memoryLocation
+  ) {
+    AliasedSSA::SSA::hasPhiInstruction(irFunc, resultType, blockStartInstr, memoryLocation)
+  } or
+  TAliasedSSAChiInstruction(
+    IRFunctionBase irFunc, Language::LanguageType resultType, TRawInstruction primaryInstruction
+  ) {
+    AliasedSSA::SSA::hasChiInstruction(irFunc, resultType, primaryInstruction)
+  } or
+  TAliasedSSAUnreachedInstruction(IRFunctionBase irFunc) {
+    AliasedSSA::SSA::hasUnreachedInstruction(irFunc)
+  }
+
+/**
+ * Provides wrappers for the constructors of each branch of `TInstruction` that is used by the
+ * unaliased SSA stage.
+ * These wrappers are not parameterized because it is not possible to invoke an IPA constructor via
+ * a class alias.
+ */
+module UnaliasedSSAInstructions {
+  class TPhiInstruction = TUnaliasedSSAPhiInstruction;
+
+  TPhiInstruction phiInstruction(
+    IRFunctionBase irFunc, Language::LanguageType resultType, TRawInstruction blockStartInstr,
+    UnaliasedSSA::SSA::MemoryLocation memoryLocation
+  ) {
+    result = TUnaliasedSSAPhiInstruction(irFunc, resultType, blockStartInstr, memoryLocation)
+  }
+
+  class TChiInstruction = TUnaliasedSSAChiInstruction;
+
+  TChiInstruction chiInstruction(
+    IRFunctionBase irFunc, Language::LanguageType resultType, TRawInstruction primaryInstruction
+  ) {
+    result = TUnaliasedSSAChiInstruction(irFunc, resultType, primaryInstruction)
+  }
+
+  class TUnreachedInstruction = TUnaliasedSSAUnreachedInstruction;
+
+  TUnreachedInstruction unreachedInstruction(IRFunctionBase irFunc) {
+    result = TUnaliasedSSAUnreachedInstruction(irFunc)
+  }
+}
+
+/**
+ * Provides wrappers for the constructors of each branch of `TInstruction` that is used by the
+ * aliased SSA stage.
+ * These wrappers are not parameterized because it is not possible to invoke an IPA constructor via
+ * a class alias.
+ */
+module AliasedSSAInstructions {
+  class TPhiInstruction = TAliasedSSAPhiInstruction;
+
+  TPhiInstruction phiInstruction(
+    IRFunctionBase irFunc, Language::LanguageType resultType, TRawInstruction blockStartInstr,
+    AliasedSSA::SSA::MemoryLocation memoryLocation
+  ) {
+    result = TAliasedSSAPhiInstruction(irFunc, resultType, blockStartInstr, memoryLocation)
+  }
+
+  class TChiInstruction = TAliasedSSAChiInstruction;
+
+  TChiInstruction chiInstruction(
+    IRFunctionBase irFunc, Language::LanguageType resultType, TRawInstruction primaryInstruction
+  ) {
+    result = TAliasedSSAChiInstruction(irFunc, resultType, primaryInstruction)
+  }
+
+  class TUnreachedInstruction = TAliasedSSAUnreachedInstruction;
+
+  TUnreachedInstruction unreachedInstruction(IRFunctionBase irFunc) {
+    result = TAliasedSSAUnreachedInstruction(irFunc)
+  }
+}

cpp/ql/src/semmle/code/cpp/ir/implementation/internal/TInstructionImports.qll

@@ -0,0 +1,2 @@
+import semmle.code.cpp.ir.implementation.IRType as IRType
+import semmle.code.cpp.ir.implementation.Opcode as Opcode

cpp/ql/src/semmle/code/cpp/ir/implementation/internal/TInstructionInternal.qll

@@ -0,0 +1,4 @@
+import semmle.code.cpp.ir.internal.IRCppLanguage as Language
+import semmle.code.cpp.ir.implementation.raw.internal.IRConstruction as IRConstruction
+import semmle.code.cpp.ir.implementation.unaliased_ssa.internal.SSAConstruction as UnaliasedSSA
+import semmle.code.cpp.ir.implementation.aliased_ssa.internal.SSAConstruction as AliasedSSA

cpp/ql/src/semmle/code/cpp/ir/implementation/raw/IRFunction.qll

@@ -1,29 +1,12 @@
 private import internal.IRInternal
+private import internal.IRFunctionImports as Imports
+import Imports::IRFunctionBase
 import Instruction
 
-private newtype TIRFunction =
-  MkIRFunction(Language::Function func) { Construction::functionHasIR(func) }
-
 /**
- * Represents the IR for a function.
+ * The IR for a function.
  */
-class IRFunction extends TIRFunction {
+class IRFunction extends IRFunctionBase {
-  Language::Function func;
-
-  IRFunction() { this = MkIRFunction(func) }
-
-  final string toString() { result = "IR: " + func.toString() }
-
-  /**
-   * Gets the function whose IR is represented.
-   */
-  final Language::Function getFunction() { result = func }
-
-  /**
-   * Gets the location of the function.
-   */
-  final Language::Location getLocation() { result = func.getLocation() }
-
   /**
    * Gets the entry point for this function.
    */

cpp/ql/src/semmle/code/cpp/ir/implementation/raw/Instruction.qll

@@ -29,7 +29,13 @@ private Instruction getAnInstructionAtLine(IRFunction irFunc, Language::File fil
 /**
  * Represents a single operation in the IR.
  */
-class Instruction extends Construction::TInstruction {
+class Instruction extends Construction::TStageInstruction {
+  Instruction() {
+    // The base `TStageInstruction` type is a superset of the actual instructions appearing in this
+    // stage. This call lets the stage filter out the ones that are not reused from raw IR.
+    Construction::hasInstruction(this)
+  }
+
   final string toString() { result = getOpcode().toString() + ": " + getAST().toString() }
 
   /**
@@ -250,7 +256,7 @@ class Instruction extends Construction::TInstruction {
    * result of the `Load` instruction is a prvalue of type `int`, representing
    * the integer value loaded from variable `x`.
    */
-  final predicate isGLValue() { Construction::getInstructionResultType(this).hasType(_, true) }
+  final predicate isGLValue() { getResultLanguageType().hasType(_, true) }
 
   /**
    * Gets the size of the result produced by this instruction, in bytes. If the
@@ -259,7 +265,7 @@ class Instruction extends Construction::TInstruction {
    * If `this.isGLValue()` holds for this instruction, the value of
    * `getResultSize()` will always be the size of a pointer.
    */
-  final int getResultSize() { result = Construction::getInstructionResultType(this).getByteSize() }
+  final int getResultSize() { result = getResultLanguageType().getByteSize() }
 
   /**
    * Gets the opcode that specifies the operation performed by this instruction.

cpp/ql/src/semmle/code/cpp/ir/implementation/raw/internal/IRConstruction.qll

@@ -1,6 +1,8 @@
 private import cpp
 import semmle.code.cpp.ir.implementation.raw.IR
 private import semmle.code.cpp.ir.implementation.internal.OperandTag
+private import semmle.code.cpp.ir.implementation.internal.IRFunctionBase
+private import semmle.code.cpp.ir.implementation.internal.TInstruction
 private import semmle.code.cpp.ir.internal.CppType
 private import semmle.code.cpp.ir.internal.Overlap
 private import semmle.code.cpp.ir.internal.TempVariableTag
@@ -12,34 +14,41 @@ private import TranslatedStmt
 private import TranslatedFunction
 
 TranslatedElement getInstructionTranslatedElement(Instruction instruction) {
-  instruction = MkInstruction(result, _)
+  instruction = TRawInstruction(_, _, _, _, result, _)
 }
 
-InstructionTag getInstructionTag(Instruction instruction) { instruction = MkInstruction(_, result) }
+InstructionTag getInstructionTag(Instruction instruction) {
-
+  instruction = TRawInstruction(_, _, _, _, _, result)
-import Cached
+}
 
+/**
+ * Provides the portion of the parameterized IR interface that is used to construct the initial
+ * "raw" stage of the IR. The other stages of the IR do not expose these predicates.
+ */
 cached
-private module Cached {
+module Raw {
+  class InstructionTag1 = TranslatedElement;
+
+  class InstructionTag2 = InstructionTag;
+
   cached
   predicate functionHasIR(Function func) { exists(getTranslatedFunction(func)) }
 
   cached
-  newtype TInstruction =
+  predicate hasInstruction(
-    MkInstruction(TranslatedElement element, InstructionTag tag) {
+    Function func, Opcode opcode, Element ast, CppType resultType, TranslatedElement element,
-      element.hasInstruction(_, tag, _)
+    InstructionTag tag
-    }
+  ) {
+    element.hasInstruction(opcode, tag, resultType) and
+    ast = element.getAST() and
+    func = element.getFunction()
+  }
 
   cached
   predicate hasUserVariable(Function func, Variable var, CppType type) {
     getTranslatedFunction(func).hasUserVariable(var, type)
   }
 
-  cached
-  predicate hasThisVariable(Function func, CppType type) {
-    type = getTypeForGLValue(getTranslatedFunction(func).getThisType())
-  }
-
   cached
   predicate hasTempVariable(Function func, Locatable ast, TempVariableTag tag, CppType type) {
     exists(TranslatedElement element |
@@ -62,6 +71,16 @@ private module Cached {
     var.hasDynamicInitialization() and
     type = getBoolType()
   }
+}
+
+import Cached
+
+cached
+private module Cached {
+  class TStageInstruction = TRawInstruction;
+
+  cached
+  predicate hasInstruction(TRawInstruction instr) { any() }
 
   cached
   predicate hasModeledMemoryResult(Instruction instruction) { none() }
@@ -267,25 +286,23 @@ private module Cached {
   }
 
   cached
-  Locatable getInstructionAST(Instruction instruction) {
+  Locatable getInstructionAST(TStageInstruction instr) {
-    result = getInstructionTranslatedElement(instruction).getAST()
+    instr = TRawInstruction(_, _, result, _, _, _)
   }
 
   cached
-  CppType getInstructionResultType(Instruction instruction) {
+  CppType getInstructionResultType(TStageInstruction instr) {
-    getInstructionTranslatedElement(instruction)
+    instr = TRawInstruction(_, _, _, result, _, _)
-        .hasInstruction(_, getInstructionTag(instruction), result)
   }
 
   cached
-  Opcode getInstructionOpcode(Instruction instruction) {
+  Opcode getInstructionOpcode(TStageInstruction instr) {
-    getInstructionTranslatedElement(instruction)
+    instr = TRawInstruction(_, result, _, _, _, _)
-        .hasInstruction(result, getInstructionTag(instruction), _)
   }
 
   cached
-  IRFunction getInstructionEnclosingIRFunction(Instruction instruction) {
+  IRFunctionBase getInstructionEnclosingIRFunction(TStageInstruction instr) {
-    result.getFunction() = getInstructionTranslatedElement(instruction).getFunction()
+    instr = TRawInstruction(result, _, _, _, _, _)
   }
 
   cached

cpp/ql/src/semmle/code/cpp/ir/implementation/raw/internal/IRFunctionImports.qll

@@ -0,0 +1 @@
+import semmle.code.cpp.ir.implementation.internal.IRFunctionBase as IRFunctionBase

cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/IRFunction.qll

@@ -1,29 +1,12 @@
 private import internal.IRInternal
+private import internal.IRFunctionImports as Imports
+import Imports::IRFunctionBase
 import Instruction
 
-private newtype TIRFunction =
-  MkIRFunction(Language::Function func) { Construction::functionHasIR(func) }
-
 /**
- * Represents the IR for a function.
+ * The IR for a function.
  */
-class IRFunction extends TIRFunction {
+class IRFunction extends IRFunctionBase {
-  Language::Function func;
-
-  IRFunction() { this = MkIRFunction(func) }
-
-  final string toString() { result = "IR: " + func.toString() }
-
-  /**
-   * Gets the function whose IR is represented.
-   */
-  final Language::Function getFunction() { result = func }
-
-  /**
-   * Gets the location of the function.
-   */
-  final Language::Location getLocation() { result = func.getLocation() }
-
   /**
    * Gets the entry point for this function.
    */

cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/Instruction.qll

@@ -29,7 +29,13 @@ private Instruction getAnInstructionAtLine(IRFunction irFunc, Language::File fil
 /**
  * Represents a single operation in the IR.
  */
-class Instruction extends Construction::TInstruction {
+class Instruction extends Construction::TStageInstruction {
+  Instruction() {
+    // The base `TStageInstruction` type is a superset of the actual instructions appearing in this
+    // stage. This call lets the stage filter out the ones that are not reused from raw IR.
+    Construction::hasInstruction(this)
+  }
+
   final string toString() { result = getOpcode().toString() + ": " + getAST().toString() }
 
   /**
@@ -250,7 +256,7 @@ class Instruction extends Construction::TInstruction {
    * result of the `Load` instruction is a prvalue of type `int`, representing
    * the integer value loaded from variable `x`.
    */
-  final predicate isGLValue() { Construction::getInstructionResultType(this).hasType(_, true) }
+  final predicate isGLValue() { getResultLanguageType().hasType(_, true) }
 
   /**
    * Gets the size of the result produced by this instruction, in bytes. If the
@@ -259,7 +265,7 @@ class Instruction extends Construction::TInstruction {
    * If `this.isGLValue()` holds for this instruction, the value of
    * `getResultSize()` will always be the size of a pointer.
    */
-  final int getResultSize() { result = Construction::getInstructionResultType(this).getByteSize() }
+  final int getResultSize() { result = getResultLanguageType().getByteSize() }
 
   /**
    * Gets the opcode that specifies the operation performed by this instruction.

cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/IRFunctionImports.qll

@@ -0,0 +1 @@
+import semmle.code.cpp.ir.implementation.internal.IRFunctionBase as IRFunctionBase

cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/SSAConstruction.qll

@@ -1,5 +1,11 @@
 import SSAConstructionInternal
-private import SSAConstructionImports
+private import SSAConstructionImports as Imports
+private import Imports::Opcode
+private import Imports::OperandTag
+private import Imports::Overlap
+private import Imports::TInstruction
+private import Imports::RawIR as RawIR
+private import SSAInstructions
 private import NewIR
 
 private class OldBlock = Reachability::ReachableBlock;
@@ -10,54 +16,35 @@ import Cached
 
 cached
 private module Cached {
+  class TStageInstruction =
+    TRawInstruction or TPhiInstruction or TChiInstruction or TUnreachedInstruction;
+
+  private TRawInstruction rawInstruction(
+    IRFunctionBase irFunc, Opcode opcode, Language::AST ast, Language::LanguageType resultType
+  ) {
+    result = TRawInstruction(irFunc, opcode, ast, resultType, _, _) and
+    result instanceof OldInstruction
+  }
+
+  cached
+  predicate hasInstruction(TStageInstruction instr) {
+    instr instanceof TRawInstruction and instr instanceof OldInstruction
+    or
+    not instr instanceof TRawInstruction
+  }
+
   private IRBlock getNewBlock(OldBlock oldBlock) {
     result.getFirstInstruction() = getNewInstruction(oldBlock.getFirstInstruction())
   }
 
   cached
-  predicate functionHasIR(Language::Function func) {
+  OldInstruction getOldInstruction(Instruction instr) { instr = result }
-    exists(OldIR::IRFunction irFunc | irFunc.getFunction() = func)
-  }
-
-  cached
-  OldInstruction getOldInstruction(Instruction instr) { instr = WrappedInstruction(result) }
 
   private IRVariable getNewIRVariable(OldIR::IRVariable var) {
     // This is just a type cast. Both classes derive from the same newtype.
     result = var
   }
 
-  cached
-  newtype TInstruction =
-    WrappedInstruction(OldInstruction oldInstruction) {
-      not oldInstruction instanceof OldIR::PhiInstruction
-    } or
-    Phi(OldBlock block, Alias::MemoryLocation defLocation) {
-      definitionHasPhiNode(defLocation, block)
-    } or
-    Chi(OldInstruction oldInstruction) {
-      not oldInstruction instanceof OldIR::PhiInstruction and
-      hasChiNode(_, oldInstruction)
-    } or
-    Unreached(Language::Function function) {
-      exists(OldInstruction oldInstruction |
-        function = oldInstruction.getEnclosingFunction() and
-        Reachability::isInfeasibleInstructionSuccessor(oldInstruction, _)
-      )
-    }
-
-  cached
-  predicate hasTempVariable(
-    Language::Function func, Language::AST ast, TempVariableTag tag, Language::LanguageType type
-  ) {
-    exists(OldIR::IRTempVariable var |
-      var.getEnclosingFunction() = func and
-      var.getAST() = ast and
-      var.getTag() = tag and
-      var.getLanguageType() = type
-    )
-  }
-
   cached
   predicate hasModeledMemoryResult(Instruction instruction) {
     exists(Alias::getResultMemoryLocation(getOldInstruction(instruction))) or
@@ -73,7 +60,7 @@ private module Cached {
     or
     // Chi instructions track virtual variables, and therefore a chi instruction is
     // conflated if it's associated with the aliased virtual variable.
-    exists(OldInstruction oldInstruction | instruction = Chi(oldInstruction) |
+    exists(OldInstruction oldInstruction | instruction = getChi(oldInstruction) |
       Alias::getResultMemoryLocation(oldInstruction).getVirtualVariable() instanceof
         Alias::AliasedVirtualVariable
     )
@@ -81,7 +68,7 @@ private module Cached {
     // Phi instructions track locations, and therefore a phi instruction is
     // conflated if it's associated with a conflated location.
     exists(Alias::MemoryLocation location |
-      instruction = Phi(_, location) and
+      instruction = getPhi(_, location) and
       not exists(location.getAllocation())
     )
   }
@@ -128,7 +115,7 @@ private module Cached {
       hasMemoryOperandDefinition(oldInstruction, oldOperand, overlap, result)
     )
     or
-    instruction = Chi(getOldInstruction(result)) and
+    instruction = getChi(getOldInstruction(result)) and
     tag instanceof ChiPartialOperandTag and
     overlap instanceof MustExactlyOverlap
     or
@@ -172,13 +159,15 @@ private module Cached {
 
   pragma[noopt]
   cached
-  Instruction getPhiOperandDefinition(Phi instr, IRBlock newPredecessorBlock, Overlap overlap) {
+  Instruction getPhiOperandDefinition(
+    PhiInstruction instr, IRBlock newPredecessorBlock, Overlap overlap
+  ) {
     exists(
       Alias::MemoryLocation defLocation, Alias::MemoryLocation useLocation, OldBlock phiBlock,
       OldBlock predBlock, OldBlock defBlock, int defOffset, Alias::MemoryLocation actualDefLocation
     |
       hasPhiOperandDefinition(defLocation, useLocation, phiBlock, predBlock, defBlock, defOffset) and
-      instr = Phi(phiBlock, useLocation) and
+      instr = getPhi(phiBlock, useLocation) and
       newPredecessorBlock = getNewBlock(predBlock) and
       result = getDefinitionOrChiInstruction(defBlock, defOffset, defLocation, actualDefLocation) and
       overlap = Alias::getOverlap(actualDefLocation, useLocation)
@@ -191,7 +180,7 @@ private module Cached {
       Alias::VirtualVariable vvar, OldInstruction oldInstr, Alias::MemoryLocation defLocation,
       OldBlock defBlock, int defRank, int defOffset, OldBlock useBlock, int useRank
     |
-      chiInstr = Chi(oldInstr) and
+      chiInstr = getChi(oldInstr) and
       vvar = Alias::getResultMemoryLocation(oldInstr).getVirtualVariable() and
       hasDefinitionAtRank(vvar, defLocation, defBlock, defRank, defOffset) and
       hasUseAtRank(vvar, useBlock, useRank, oldInstr) and
@@ -203,7 +192,7 @@ private module Cached {
   cached
   Instruction getPhiInstructionBlockStart(PhiInstruction instr) {
     exists(OldBlock oldBlock |
-      instr = Phi(oldBlock, _) and
+      instr = getPhi(oldBlock, _) and
       result = getNewInstruction(oldBlock.getFirstInstruction())
     )
   }
@@ -228,20 +217,20 @@ private module Cached {
   Instruction getInstructionSuccessor(Instruction instruction, EdgeKind kind) {
     if hasChiNode(_, getOldInstruction(instruction))
     then
-      result = Chi(getOldInstruction(instruction)) and
+      result = getChi(getOldInstruction(instruction)) and
       kind instanceof GotoEdge
     else (
       exists(OldInstruction oldInstruction |
         oldInstruction = getOldInstruction(instruction) and
         (
           if Reachability::isInfeasibleInstructionSuccessor(oldInstruction, kind)
-          then result = Unreached(instruction.getEnclosingFunction())
+          then result = unreachedInstruction(instruction.getEnclosingIRFunction())
           else result = getNewInstruction(oldInstruction.getSuccessor(kind))
         )
       )
       or
       exists(OldInstruction oldInstruction |
-        instruction = Chi(oldInstruction) and
+        instruction = getChi(oldInstruction) and
         result = getNewInstruction(oldInstruction.getSuccessor(kind))
       )
     )
@@ -260,84 +249,61 @@ private module Cached {
       // `oldInstruction`, in which case the back edge should come out of the
       // chi node instead.
       if hasChiNode(_, oldInstruction)
-      then instruction = Chi(oldInstruction)
+      then instruction = getChi(oldInstruction)
       else instruction = getNewInstruction(oldInstruction)
     )
   }
 
   cached
-  Language::AST getInstructionAST(Instruction instruction) {
+  Language::AST getInstructionAST(TStageInstruction instr) {
-    exists(OldInstruction oldInstruction |
+    instr = rawInstruction(_, _, result, _)
-      instruction = WrappedInstruction(oldInstruction)
+    or
-      or
+    exists(RawIR::Instruction blockStartInstr |
-      instruction = Chi(oldInstruction)
+      instr = phiInstruction(_, _, blockStartInstr, _) and
-    |
+      result = blockStartInstr.getAST()
-      result = oldInstruction.getAST()
     )
     or
-    exists(OldBlock block |
+    exists(RawIR::Instruction primaryInstr |
-      instruction = Phi(block, _) and
+      instr = chiInstruction(_, _, primaryInstr) and
-      result = block.getFirstInstruction().getAST()
+      result = primaryInstr.getAST()
     )
     or
-    instruction = Unreached(result)
+    exists(IRFunctionBase irFunc |
+      instr = unreachedInstruction(irFunc) and result = irFunc.getFunction()
+    )
   }
 
   cached
-  Language::LanguageType getInstructionResultType(Instruction instruction) {
+  Language::LanguageType getInstructionResultType(TStageInstruction instr) {
-    exists(OldInstruction oldInstruction |
+    instr = rawInstruction(_, _, _, result)
-      instruction = WrappedInstruction(oldInstruction) and
-      result = oldInstruction.getResultLanguageType()
-    )
     or
-    exists(OldInstruction oldInstruction, Alias::VirtualVariable vvar |
+    instr = phiInstruction(_, result, _, _)
-      instruction = Chi(oldInstruction) and
-      hasChiNode(vvar, oldInstruction) and
-      result = vvar.getType()
-    )
     or
-    exists(Alias::MemoryLocation location |
+    instr = chiInstruction(_, result, _)
-      instruction = Phi(_, location) and
-      result = location.getType()
-    )
     or
-    instruction = Unreached(_) and
+    instr = unreachedInstruction(_) and result = Language::getVoidType()
-    result = Language::getVoidType()
   }
 
   cached
-  Opcode getInstructionOpcode(Instruction instruction) {
+  Opcode getInstructionOpcode(TStageInstruction instr) {
-    exists(OldInstruction oldInstruction |
+    instr = rawInstruction(_, result, _, _)
-      instruction = WrappedInstruction(oldInstruction) and
-      result = oldInstruction.getOpcode()
-    )
     or
-    instruction instanceof Chi and
+    instr = phiInstruction(_, _, _, _) and result instanceof Opcode::Phi
-    result instanceof Opcode::Chi
     or
-    instruction instanceof Phi and
+    instr = chiInstruction(_, _, _) and result instanceof Opcode::Chi
-    result instanceof Opcode::Phi
     or
-    instruction instanceof Unreached and
+    instr = unreachedInstruction(_) and result instanceof Opcode::Unreached
-    result instanceof Opcode::Unreached
   }
 
   cached
-  IRFunction getInstructionEnclosingIRFunction(Instruction instruction) {
+  IRFunctionBase getInstructionEnclosingIRFunction(TStageInstruction instr) {
-    exists(OldInstruction oldInstruction |
+    instr = rawInstruction(result, _, _, _)
-      instruction = WrappedInstruction(oldInstruction)
-      or
-      instruction = Chi(oldInstruction)
-    |
-      result.getFunction() = oldInstruction.getEnclosingFunction()
-    )
     or
-    exists(OldBlock block |
+    instr = phiInstruction(result, _, _, _)
-      instruction = Phi(block, _) and
-      result.getFunction() = block.getEnclosingFunction()
-    )
     or
-    instruction = Unreached(result.getFunction())
+    instr = chiInstruction(result, _, _)
+    or
+    instr = unreachedInstruction(result)
   }
 
   cached
@@ -401,7 +367,7 @@ private module Cached {
     )
     or
     exists(OldIR::Instruction oldInstruction |
-      instruction = Chi(oldInstruction) and
+      instruction = getChi(oldInstruction) and
       result = getNewInstruction(oldInstruction)
     )
   }
@@ -409,6 +375,14 @@ private module Cached {
 
 private Instruction getNewInstruction(OldInstruction instr) { getOldInstruction(result) = instr }
 
+private ChiInstruction getChi(OldInstruction primaryInstr) {
+  result = chiInstruction(_, _, primaryInstr)
+}
+
+private PhiInstruction getPhi(OldBlock defBlock, Alias::MemoryLocation defLocation) {
+  result = phiInstruction(_, _, defBlock.getFirstInstruction(), defLocation)
+}
+
 /**
  * Holds if instruction `def` needs to have a `Chi` instruction inserted after it, to account for a partial definition
  * of a virtual variable. The `Chi` instruction provides a definition of the entire virtual variable of which the
@@ -588,7 +562,7 @@ module DefUse {
     |
       // An odd offset corresponds to the `Chi` instruction.
       defOffset = oldOffset * 2 + 1 and
-      result = Chi(oldInstr) and
+      result = getChi(oldInstr) and
       (
         defLocation = Alias::getResultMemoryLocation(oldInstr) or
         defLocation = Alias::getResultMemoryLocation(oldInstr).getVirtualVariable()
@@ -607,7 +581,7 @@ module DefUse {
     or
     defOffset = -1 and
     hasDefinition(_, defLocation, defBlock, defOffset) and
-    result = Phi(defBlock, defLocation) and
+    result = getPhi(defBlock, defLocation) and
     actualDefLocation = defLocation
   }
 
@@ -891,7 +865,7 @@ private module CachedForDebugging {
     )
     or
     exists(Alias::MemoryLocation location, OldBlock phiBlock, string specificity |
-      instr = Phi(phiBlock, location) and
+      instr = getPhi(phiBlock, location) and
       result =
         "Phi Block(" + phiBlock.getUniqueId() + ")[" + specificity + "]: " + location.getUniqueId() and
       if location instanceof Alias::VirtualVariable
@@ -901,7 +875,7 @@ private module CachedForDebugging {
       else specificity = "s"
     )
     or
-    instr = Unreached(_) and
+    instr = unreachedInstruction(_) and
     result = "Unreached"
   }
 
@@ -961,3 +935,44 @@ module SSAConsistency {
     )
   }
 }
+
+/**
+ * Provides the portion of the parameterized IR interface that is used to construct the SSA stages
+ * of the IR. The raw stage of the IR does not expose these predicates.
+ */
+cached
+module SSA {
+  class MemoryLocation = Alias::MemoryLocation;
+
+  cached
+  predicate hasPhiInstruction(
+    IRFunction irFunc, Language::LanguageType resultType, OldInstruction blockStartInstr,
+    Alias::MemoryLocation defLocation
+  ) {
+    exists(OldBlock oldBlock |
+      definitionHasPhiNode(defLocation, oldBlock) and
+      irFunc = oldBlock.getEnclosingIRFunction() and
+      blockStartInstr = oldBlock.getFirstInstruction() and
+      resultType = defLocation.getType()
+    )
+  }
+
+  cached
+  predicate hasChiInstruction(
+    IRFunctionBase irFunc, Language::LanguageType resultType, OldInstruction primaryInstruction
+  ) {
+    exists(Alias::VirtualVariable vvar |
+      hasChiNode(vvar, primaryInstruction) and
+      irFunc = primaryInstruction.getEnclosingIRFunction() and
+      resultType = vvar.getType()
+    )
+  }
+
+  cached
+  predicate hasUnreachedInstruction(IRFunction irFunc) {
+    exists(OldInstruction oldInstruction |
+      irFunc = oldInstruction.getEnclosingIRFunction() and
+      Reachability::isInfeasibleInstructionSuccessor(oldInstruction, _)
+    )
+  }
+}

cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/SSAConstructionImports.qll

@@ -1,3 +1,5 @@
-import semmle.code.cpp.ir.implementation.Opcode
+import semmle.code.cpp.ir.implementation.Opcode as Opcode
-import semmle.code.cpp.ir.implementation.internal.OperandTag
+import semmle.code.cpp.ir.implementation.internal.OperandTag as OperandTag
-import semmle.code.cpp.ir.internal.Overlap
+import semmle.code.cpp.ir.internal.Overlap as Overlap
+import semmle.code.cpp.ir.implementation.internal.TInstruction as TInstruction
+import semmle.code.cpp.ir.implementation.raw.IR as RawIR

cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/SSAConstructionInternal.qll

@@ -2,5 +2,7 @@ import semmle.code.cpp.ir.implementation.raw.IR as OldIR
 import semmle.code.cpp.ir.implementation.raw.internal.reachability.ReachableBlock as Reachability
 import semmle.code.cpp.ir.implementation.raw.internal.reachability.Dominance as Dominance
 import semmle.code.cpp.ir.implementation.unaliased_ssa.IR as NewIR
+import semmle.code.cpp.ir.implementation.raw.internal.IRConstruction as RawStage
+import semmle.code.cpp.ir.implementation.internal.TInstruction::UnaliasedSSAInstructions as SSAInstructions
 import semmle.code.cpp.ir.internal.IRCppLanguage as Language
 import SimpleSSA as Alias

csharp/ql/src/semmle/code/csharp/ir/implementation/raw/IRFunction.qll

@@ -1,29 +1,12 @@
 private import internal.IRInternal
+private import internal.IRFunctionImports as Imports
+import Imports::IRFunctionBase
 import Instruction
 
-private newtype TIRFunction =
-  MkIRFunction(Language::Function func) { Construction::functionHasIR(func) }
-
 /**
- * Represents the IR for a function.
+ * The IR for a function.
  */
-class IRFunction extends TIRFunction {
+class IRFunction extends IRFunctionBase {
-  Language::Function func;
-
-  IRFunction() { this = MkIRFunction(func) }
-
-  final string toString() { result = "IR: " + func.toString() }
-
-  /**
-   * Gets the function whose IR is represented.
-   */
-  final Language::Function getFunction() { result = func }
-
-  /**
-   * Gets the location of the function.
-   */
-  final Language::Location getLocation() { result = func.getLocation() }
-
   /**
    * Gets the entry point for this function.
    */

csharp/ql/src/semmle/code/csharp/ir/implementation/raw/Instruction.qll

@@ -29,7 +29,13 @@ private Instruction getAnInstructionAtLine(IRFunction irFunc, Language::File fil
 /**
  * Represents a single operation in the IR.
  */
-class Instruction extends Construction::TInstruction {
+class Instruction extends Construction::TStageInstruction {
+  Instruction() {
+    // The base `TStageInstruction` type is a superset of the actual instructions appearing in this
+    // stage. This call lets the stage filter out the ones that are not reused from raw IR.
+    Construction::hasInstruction(this)
+  }
+
   final string toString() { result = getOpcode().toString() + ": " + getAST().toString() }
 
   /**
@@ -250,7 +256,7 @@ class Instruction extends Construction::TInstruction {
    * result of the `Load` instruction is a prvalue of type `int`, representing
    * the integer value loaded from variable `x`.
    */
-  final predicate isGLValue() { Construction::getInstructionResultType(this).hasType(_, true) }
+  final predicate isGLValue() { getResultLanguageType().hasType(_, true) }
 
   /**
    * Gets the size of the result produced by this instruction, in bytes. If the
@@ -259,7 +265,7 @@ class Instruction extends Construction::TInstruction {
    * If `this.isGLValue()` holds for this instruction, the value of
    * `getResultSize()` will always be the size of a pointer.
    */
-  final int getResultSize() { result = Construction::getInstructionResultType(this).getByteSize() }
+  final int getResultSize() { result = getResultLanguageType().getByteSize() }
 
   /**
    * Gets the opcode that specifies the operation performed by this instruction.

csharp/ql/src/semmle/code/csharp/ir/implementation/unaliased_ssa/IRFunction.qll

@@ -1,29 +1,12 @@
 private import internal.IRInternal
+private import internal.IRFunctionImports as Imports
+import Imports::IRFunctionBase
 import Instruction
 
-private newtype TIRFunction =
-  MkIRFunction(Language::Function func) { Construction::functionHasIR(func) }
-
 /**
- * Represents the IR for a function.
+ * The IR for a function.
  */
-class IRFunction extends TIRFunction {
+class IRFunction extends IRFunctionBase {
-  Language::Function func;
-
-  IRFunction() { this = MkIRFunction(func) }
-
-  final string toString() { result = "IR: " + func.toString() }
-
-  /**
-   * Gets the function whose IR is represented.
-   */
-  final Language::Function getFunction() { result = func }
-
-  /**
-   * Gets the location of the function.
-   */
-  final Language::Location getLocation() { result = func.getLocation() }
-
   /**
    * Gets the entry point for this function.
    */

csharp/ql/src/semmle/code/csharp/ir/implementation/unaliased_ssa/Instruction.qll

@@ -29,7 +29,13 @@ private Instruction getAnInstructionAtLine(IRFunction irFunc, Language::File fil
 /**
  * Represents a single operation in the IR.
  */
-class Instruction extends Construction::TInstruction {
+class Instruction extends Construction::TStageInstruction {
+  Instruction() {
+    // The base `TStageInstruction` type is a superset of the actual instructions appearing in this
+    // stage. This call lets the stage filter out the ones that are not reused from raw IR.
+    Construction::hasInstruction(this)
+  }
+
   final string toString() { result = getOpcode().toString() + ": " + getAST().toString() }
 
   /**
@@ -250,7 +256,7 @@ class Instruction extends Construction::TInstruction {
    * result of the `Load` instruction is a prvalue of type `int`, representing
    * the integer value loaded from variable `x`.
    */
-  final predicate isGLValue() { Construction::getInstructionResultType(this).hasType(_, true) }
+  final predicate isGLValue() { getResultLanguageType().hasType(_, true) }
 
   /**
    * Gets the size of the result produced by this instruction, in bytes. If the
@@ -259,7 +265,7 @@ class Instruction extends Construction::TInstruction {
    * If `this.isGLValue()` holds for this instruction, the value of
    * `getResultSize()` will always be the size of a pointer.
    */
-  final int getResultSize() { result = Construction::getInstructionResultType(this).getByteSize() }
+  final int getResultSize() { result = getResultLanguageType().getByteSize() }
 
   /**
    * Gets the opcode that specifies the operation performed by this instruction.

csharp/ql/src/semmle/code/csharp/ir/implementation/unaliased_ssa/internal/SSAConstruction.qll

@@ -1,5 +1,11 @@
 import SSAConstructionInternal
-private import SSAConstructionImports
+private import SSAConstructionImports as Imports
+private import Imports::Opcode
+private import Imports::OperandTag
+private import Imports::Overlap
+private import Imports::TInstruction
+private import Imports::RawIR as RawIR
+private import SSAInstructions
 private import NewIR
 
 private class OldBlock = Reachability::ReachableBlock;
@@ -10,54 +16,35 @@ import Cached
 
 cached
 private module Cached {
+  class TStageInstruction =
+    TRawInstruction or TPhiInstruction or TChiInstruction or TUnreachedInstruction;
+
+  private TRawInstruction rawInstruction(
+    IRFunctionBase irFunc, Opcode opcode, Language::AST ast, Language::LanguageType resultType
+  ) {
+    result = TRawInstruction(irFunc, opcode, ast, resultType, _, _) and
+    result instanceof OldInstruction
+  }
+
+  cached
+  predicate hasInstruction(TStageInstruction instr) {
+    instr instanceof TRawInstruction and instr instanceof OldInstruction
+    or
+    not instr instanceof TRawInstruction
+  }
+
   private IRBlock getNewBlock(OldBlock oldBlock) {
     result.getFirstInstruction() = getNewInstruction(oldBlock.getFirstInstruction())
   }
 
   cached
-  predicate functionHasIR(Language::Function func) {
+  OldInstruction getOldInstruction(Instruction instr) { instr = result }
-    exists(OldIR::IRFunction irFunc | irFunc.getFunction() = func)
-  }
-
-  cached
-  OldInstruction getOldInstruction(Instruction instr) { instr = WrappedInstruction(result) }
 
   private IRVariable getNewIRVariable(OldIR::IRVariable var) {
     // This is just a type cast. Both classes derive from the same newtype.
     result = var
   }
 
-  cached
-  newtype TInstruction =
-    WrappedInstruction(OldInstruction oldInstruction) {
-      not oldInstruction instanceof OldIR::PhiInstruction
-    } or
-    Phi(OldBlock block, Alias::MemoryLocation defLocation) {
-      definitionHasPhiNode(defLocation, block)
-    } or
-    Chi(OldInstruction oldInstruction) {
-      not oldInstruction instanceof OldIR::PhiInstruction and
-      hasChiNode(_, oldInstruction)
-    } or
-    Unreached(Language::Function function) {
-      exists(OldInstruction oldInstruction |
-        function = oldInstruction.getEnclosingFunction() and
-        Reachability::isInfeasibleInstructionSuccessor(oldInstruction, _)
-      )
-    }
-
-  cached
-  predicate hasTempVariable(
-    Language::Function func, Language::AST ast, TempVariableTag tag, Language::LanguageType type
-  ) {
-    exists(OldIR::IRTempVariable var |
-      var.getEnclosingFunction() = func and
-      var.getAST() = ast and
-      var.getTag() = tag and
-      var.getLanguageType() = type
-    )
-  }
-
   cached
   predicate hasModeledMemoryResult(Instruction instruction) {
     exists(Alias::getResultMemoryLocation(getOldInstruction(instruction))) or
@@ -73,7 +60,7 @@ private module Cached {
     or
     // Chi instructions track virtual variables, and therefore a chi instruction is
     // conflated if it's associated with the aliased virtual variable.
-    exists(OldInstruction oldInstruction | instruction = Chi(oldInstruction) |
+    exists(OldInstruction oldInstruction | instruction = getChi(oldInstruction) |
       Alias::getResultMemoryLocation(oldInstruction).getVirtualVariable() instanceof
         Alias::AliasedVirtualVariable
     )
@@ -81,7 +68,7 @@ private module Cached {
     // Phi instructions track locations, and therefore a phi instruction is
     // conflated if it's associated with a conflated location.
     exists(Alias::MemoryLocation location |
-      instruction = Phi(_, location) and
+      instruction = getPhi(_, location) and
       not exists(location.getAllocation())
     )
   }
@@ -128,7 +115,7 @@ private module Cached {
       hasMemoryOperandDefinition(oldInstruction, oldOperand, overlap, result)
     )
     or
-    instruction = Chi(getOldInstruction(result)) and
+    instruction = getChi(getOldInstruction(result)) and
     tag instanceof ChiPartialOperandTag and
     overlap instanceof MustExactlyOverlap
     or
@@ -172,13 +159,15 @@ private module Cached {
 
   pragma[noopt]
   cached
-  Instruction getPhiOperandDefinition(Phi instr, IRBlock newPredecessorBlock, Overlap overlap) {
+  Instruction getPhiOperandDefinition(
+    PhiInstruction instr, IRBlock newPredecessorBlock, Overlap overlap
+  ) {
     exists(
       Alias::MemoryLocation defLocation, Alias::MemoryLocation useLocation, OldBlock phiBlock,
       OldBlock predBlock, OldBlock defBlock, int defOffset, Alias::MemoryLocation actualDefLocation
     |
       hasPhiOperandDefinition(defLocation, useLocation, phiBlock, predBlock, defBlock, defOffset) and
-      instr = Phi(phiBlock, useLocation) and
+      instr = getPhi(phiBlock, useLocation) and
       newPredecessorBlock = getNewBlock(predBlock) and
       result = getDefinitionOrChiInstruction(defBlock, defOffset, defLocation, actualDefLocation) and
       overlap = Alias::getOverlap(actualDefLocation, useLocation)
@@ -191,7 +180,7 @@ private module Cached {
       Alias::VirtualVariable vvar, OldInstruction oldInstr, Alias::MemoryLocation defLocation,
       OldBlock defBlock, int defRank, int defOffset, OldBlock useBlock, int useRank
     |
-      chiInstr = Chi(oldInstr) and
+      chiInstr = getChi(oldInstr) and
       vvar = Alias::getResultMemoryLocation(oldInstr).getVirtualVariable() and
       hasDefinitionAtRank(vvar, defLocation, defBlock, defRank, defOffset) and
       hasUseAtRank(vvar, useBlock, useRank, oldInstr) and
@@ -203,7 +192,7 @@ private module Cached {
   cached
   Instruction getPhiInstructionBlockStart(PhiInstruction instr) {
     exists(OldBlock oldBlock |
-      instr = Phi(oldBlock, _) and
+      instr = getPhi(oldBlock, _) and
       result = getNewInstruction(oldBlock.getFirstInstruction())
     )
   }
@@ -228,20 +217,20 @@ private module Cached {
   Instruction getInstructionSuccessor(Instruction instruction, EdgeKind kind) {
     if hasChiNode(_, getOldInstruction(instruction))
     then
-      result = Chi(getOldInstruction(instruction)) and
+      result = getChi(getOldInstruction(instruction)) and
       kind instanceof GotoEdge
     else (
       exists(OldInstruction oldInstruction |
         oldInstruction = getOldInstruction(instruction) and
         (
           if Reachability::isInfeasibleInstructionSuccessor(oldInstruction, kind)
-          then result = Unreached(instruction.getEnclosingFunction())
+          then result = unreachedInstruction(instruction.getEnclosingIRFunction())
           else result = getNewInstruction(oldInstruction.getSuccessor(kind))
         )
       )
       or
       exists(OldInstruction oldInstruction |
-        instruction = Chi(oldInstruction) and
+        instruction = getChi(oldInstruction) and
         result = getNewInstruction(oldInstruction.getSuccessor(kind))
       )
     )
@@ -260,84 +249,61 @@ private module Cached {
       // `oldInstruction`, in which case the back edge should come out of the
       // chi node instead.
       if hasChiNode(_, oldInstruction)
-      then instruction = Chi(oldInstruction)
+      then instruction = getChi(oldInstruction)
       else instruction = getNewInstruction(oldInstruction)
     )
   }
 
   cached
-  Language::AST getInstructionAST(Instruction instruction) {
+  Language::AST getInstructionAST(TStageInstruction instr) {
-    exists(OldInstruction oldInstruction |
+    instr = rawInstruction(_, _, result, _)
-      instruction = WrappedInstruction(oldInstruction)
+    or
-      or
+    exists(RawIR::Instruction blockStartInstr |
-      instruction = Chi(oldInstruction)
+      instr = phiInstruction(_, _, blockStartInstr, _) and
-    |
+      result = blockStartInstr.getAST()
-      result = oldInstruction.getAST()
     )
     or
-    exists(OldBlock block |
+    exists(RawIR::Instruction primaryInstr |
-      instruction = Phi(block, _) and
+      instr = chiInstruction(_, _, primaryInstr) and
-      result = block.getFirstInstruction().getAST()
+      result = primaryInstr.getAST()
     )
     or
-    instruction = Unreached(result)
+    exists(IRFunctionBase irFunc |
+      instr = unreachedInstruction(irFunc) and result = irFunc.getFunction()
+    )
   }
 
   cached
-  Language::LanguageType getInstructionResultType(Instruction instruction) {
+  Language::LanguageType getInstructionResultType(TStageInstruction instr) {
-    exists(OldInstruction oldInstruction |
+    instr = rawInstruction(_, _, _, result)
-      instruction = WrappedInstruction(oldInstruction) and
-      result = oldInstruction.getResultLanguageType()
-    )
     or
-    exists(OldInstruction oldInstruction, Alias::VirtualVariable vvar |
+    instr = phiInstruction(_, result, _, _)
-      instruction = Chi(oldInstruction) and
-      hasChiNode(vvar, oldInstruction) and
-      result = vvar.getType()
-    )
     or
-    exists(Alias::MemoryLocation location |
+    instr = chiInstruction(_, result, _)
-      instruction = Phi(_, location) and
-      result = location.getType()
-    )
     or
-    instruction = Unreached(_) and
+    instr = unreachedInstruction(_) and result = Language::getVoidType()
-    result = Language::getVoidType()
   }
 
   cached
-  Opcode getInstructionOpcode(Instruction instruction) {
+  Opcode getInstructionOpcode(TStageInstruction instr) {
-    exists(OldInstruction oldInstruction |
+    instr = rawInstruction(_, result, _, _)
-      instruction = WrappedInstruction(oldInstruction) and
-      result = oldInstruction.getOpcode()
-    )
     or
-    instruction instanceof Chi and
+    instr = phiInstruction(_, _, _, _) and result instanceof Opcode::Phi
-    result instanceof Opcode::Chi
     or
-    instruction instanceof Phi and
+    instr = chiInstruction(_, _, _) and result instanceof Opcode::Chi
-    result instanceof Opcode::Phi
     or
-    instruction instanceof Unreached and
+    instr = unreachedInstruction(_) and result instanceof Opcode::Unreached
-    result instanceof Opcode::Unreached
   }
 
   cached
-  IRFunction getInstructionEnclosingIRFunction(Instruction instruction) {
+  IRFunctionBase getInstructionEnclosingIRFunction(TStageInstruction instr) {
-    exists(OldInstruction oldInstruction |
+    instr = rawInstruction(result, _, _, _)
-      instruction = WrappedInstruction(oldInstruction)
-      or
-      instruction = Chi(oldInstruction)
-    |
-      result.getFunction() = oldInstruction.getEnclosingFunction()
-    )
     or
-    exists(OldBlock block |
+    instr = phiInstruction(result, _, _, _)
-      instruction = Phi(block, _) and
-      result.getFunction() = block.getEnclosingFunction()
-    )
     or
-    instruction = Unreached(result.getFunction())
+    instr = chiInstruction(result, _, _)
+    or
+    instr = unreachedInstruction(result)
   }
 
   cached
@@ -401,7 +367,7 @@ private module Cached {
     )
     or
     exists(OldIR::Instruction oldInstruction |
-      instruction = Chi(oldInstruction) and
+      instruction = getChi(oldInstruction) and
       result = getNewInstruction(oldInstruction)
     )
   }
@@ -409,6 +375,14 @@ private module Cached {
 
 private Instruction getNewInstruction(OldInstruction instr) { getOldInstruction(result) = instr }
 
+private ChiInstruction getChi(OldInstruction primaryInstr) {
+  result = chiInstruction(_, _, primaryInstr)
+}
+
+private PhiInstruction getPhi(OldBlock defBlock, Alias::MemoryLocation defLocation) {
+  result = phiInstruction(_, _, defBlock.getFirstInstruction(), defLocation)
+}
+
 /**
  * Holds if instruction `def` needs to have a `Chi` instruction inserted after it, to account for a partial definition
  * of a virtual variable. The `Chi` instruction provides a definition of the entire virtual variable of which the
@@ -588,7 +562,7 @@ module DefUse {
     |
       // An odd offset corresponds to the `Chi` instruction.
       defOffset = oldOffset * 2 + 1 and
-      result = Chi(oldInstr) and
+      result = getChi(oldInstr) and
       (
         defLocation = Alias::getResultMemoryLocation(oldInstr) or
         defLocation = Alias::getResultMemoryLocation(oldInstr).getVirtualVariable()
@@ -607,7 +581,7 @@ module DefUse {
     or
     defOffset = -1 and
     hasDefinition(_, defLocation, defBlock, defOffset) and
-    result = Phi(defBlock, defLocation) and
+    result = getPhi(defBlock, defLocation) and
     actualDefLocation = defLocation
   }
 
@@ -891,7 +865,7 @@ private module CachedForDebugging {
     )
     or
     exists(Alias::MemoryLocation location, OldBlock phiBlock, string specificity |
-      instr = Phi(phiBlock, location) and
+      instr = getPhi(phiBlock, location) and
       result =
         "Phi Block(" + phiBlock.getUniqueId() + ")[" + specificity + "]: " + location.getUniqueId() and
       if location instanceof Alias::VirtualVariable
@@ -901,7 +875,7 @@ private module CachedForDebugging {
       else specificity = "s"
     )
     or
-    instr = Unreached(_) and
+    instr = unreachedInstruction(_) and
     result = "Unreached"
   }
 
@@ -961,3 +935,44 @@ module SSAConsistency {
     )
   }
 }
+
+/**
+ * Provides the portion of the parameterized IR interface that is used to construct the SSA stages
+ * of the IR. The raw stage of the IR does not expose these predicates.
+ */
+cached
+module SSA {
+  class MemoryLocation = Alias::MemoryLocation;
+
+  cached
+  predicate hasPhiInstruction(
+    IRFunction irFunc, Language::LanguageType resultType, OldInstruction blockStartInstr,
+    Alias::MemoryLocation defLocation
+  ) {
+    exists(OldBlock oldBlock |
+      definitionHasPhiNode(defLocation, oldBlock) and
+      irFunc = oldBlock.getEnclosingIRFunction() and
+      blockStartInstr = oldBlock.getFirstInstruction() and
+      resultType = defLocation.getType()
+    )
+  }
+
+  cached
+  predicate hasChiInstruction(
+    IRFunctionBase irFunc, Language::LanguageType resultType, OldInstruction primaryInstruction
+  ) {
+    exists(Alias::VirtualVariable vvar |
+      hasChiNode(vvar, primaryInstruction) and
+      irFunc = primaryInstruction.getEnclosingIRFunction() and
+      resultType = vvar.getType()
+    )
+  }
+
+  cached
+  predicate hasUnreachedInstruction(IRFunction irFunc) {
+    exists(OldInstruction oldInstruction |
+      irFunc = oldInstruction.getEnclosingIRFunction() and
+      Reachability::isInfeasibleInstructionSuccessor(oldInstruction, _)
+    )
+  }
+}