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C++ IR: Remove redundant check for same function

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The check that an instruction is in the same function as its operands is
hopefully redundant and can be removed. Just to be sure, I've added the
check to a sanity query.

This check turned out to cause bad performance in the alias analysis
because it got inlined into `AliasAnalysis::resultEscapes` and then
pulled out to a loop-invariant predicate that got a bad join order. With
this check removed, the `ssa/AliasAnalysis.qll` file is orders of
magnitude faster.
This commit is contained in:
Jonas Jensen
2018-08-09 15:19:04 +02:00
parent badb167962
commit 8c06a68835
3 changed files with 21 additions and 3 deletions
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8
cpp/ql/src/semmle/code/cpp/ir/internal/Instruction.qll
View File

@@ -66,6 +66,13 @@ module InstructionSanity {
count(instr.getOperand(tag)) > 1 and
not tag instanceof UnmodeledUseOperand
}
query predicate operandAcrossFunctions(
Instruction op, Instruction operand, OperandTag tag
) {
operand = op.getOperand(tag) and
operand.getFunctionIR() != op.getFunctionIR()
}
}
/**
@@ -302,7 +309,6 @@ class Instruction extends Construction::TInstruction {
* an operand with tag `useTag`.
*/
final predicate hasUse(Instruction useInstruction, OperandTag useTag) {
useInstruction.getFunctionIR() = funcIR and
this = useInstruction.getOperand(useTag)
}
}

8
cpp/ql/src/semmle/code/cpp/ssa/internal/aliased_ssa/Instruction.qll
View File

@@ -66,6 +66,13 @@ module InstructionSanity {
count(instr.getOperand(tag)) > 1 and
not tag instanceof UnmodeledUseOperand
}
query predicate operandAcrossFunctions(
Instruction op, Instruction operand, OperandTag tag
) {
operand = op.getOperand(tag) and
operand.getFunctionIR() != op.getFunctionIR()
}
}
/**
@@ -302,7 +309,6 @@ class Instruction extends Construction::TInstruction {
* an operand with tag `useTag`.
*/
final predicate hasUse(Instruction useInstruction, OperandTag useTag) {
useInstruction.getFunctionIR() = funcIR and
this = useInstruction.getOperand(useTag)
}
}

8
cpp/ql/src/semmle/code/cpp/ssa/internal/ssa/Instruction.qll
View File

@@ -66,6 +66,13 @@ module InstructionSanity {
count(instr.getOperand(tag)) > 1 and
not tag instanceof UnmodeledUseOperand
}
query predicate operandAcrossFunctions(
Instruction op, Instruction operand, OperandTag tag
) {
operand = op.getOperand(tag) and
operand.getFunctionIR() != op.getFunctionIR()
}
}
/**
@@ -302,7 +309,6 @@ class Instruction extends Construction::TInstruction {
* an operand with tag `useTag`.
*/
final predicate hasUse(Instruction useInstruction, OperandTag useTag) {
useInstruction.getFunctionIR() = funcIR and
this = useInstruction.getOperand(useTag)
}
}