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fold compound-assign write into the compound-rhs instruction
A compound assignment (`x += y`) previously produced two sequential control-flow nodes: a 'compound-rhs' node computing the binary operation `x + y`, followed by an 'assign:0' write node storing the result. Make the compound-rhs instruction itself perform the write (it becomes a WriteInstruction whose right-hand side is its own value), and stop emitting the separate assign:0 node for compound assignments. This saves one CFG node per compound assignment while preserving the BinaryOperationNode model (so string-concatenation taint through `s += ...` still holds) and SSA semantics (the def value is the binary operation).
This commit is contained in:
Owen Mansel-Chan
@@ -502,6 +502,11 @@ module GoCfg {
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exists(int i |
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(
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notBlankIdent(n.(Go::Assignment).getLhs(i)) and
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// A compound assignment (`x += y`) folds its write into the
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// `compound-rhs` binary-operation instruction rather than emitting a
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// separate `assign:i` write node (see
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// `IR::EvalCompoundAssignRhsInstruction`).
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not n instanceof Go::CompoundAssignStmt and
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// The `y := x.(type)` test statement of a type switch is transparent
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// (see `skipCfg`): the per-case implicit variables are written at the
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// case match nodes (see `IR::TypeSwitchImplicitVariableInstruction`),
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@@ -1139,7 +1144,10 @@ module GoCfg {
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)
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or
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(
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notBlankIdent(assgn.(Go::Assignment).getLhs(j))
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notBlankIdent(assgn.(Go::Assignment).getLhs(j)) and
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// Compound assignments fold their write into `compound-rhs` (ord -1)
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// above, so they emit no separate `assign:j` node.
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not assgn instanceof Go::CompoundAssignStmt
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or
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notBlankIdent(assgn.(Go::ValueSpec).getNameExpr(j))
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or
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@@ -726,8 +726,6 @@ module IR {
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implicitInitInstruction(any(ValueEntity v | spec.getNameExpr(i) = v.getDeclaration()))
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)
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or
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result.(EvalCompoundAssignRhsInstruction).isAdditional(assgn, "compound-rhs")
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or
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result.(ExtractTupleElementInstruction).isAdditional(assgn, "extract:" + i.toString())
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}
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@@ -735,9 +733,11 @@ module IR {
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}
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/**
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* An instruction that computes the (implicit) right-hand side of a compound assignment.
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* An instruction that computes the (implicit) right-hand side of a compound assignment,
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* such as the `x + y` in `x += y`, and writes the resulting value to the assignment's
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* left-hand side.
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*/
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class EvalCompoundAssignRhsInstruction extends Instruction {
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class EvalCompoundAssignRhsInstruction extends WriteInstruction {
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CompoundAssignStmt assgn;
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EvalCompoundAssignRhsInstruction() { this.isAdditional(assgn, "compound-rhs") }
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@@ -745,6 +745,8 @@ module IR {
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/** Gets the corresponding compound assignment statement. */
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CompoundAssignStmt getAssignment() { result = assgn }
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override Instruction getRhs() { result = this }
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override Type getResultType() { result = assgn.getRhs().getType() }
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override ControlFlow::Root getRoot() { result.isRootOf(assgn) }
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@@ -1228,6 +1230,10 @@ module IR {
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or
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exists(IncDecStmt ids | write.isIn(ids) | lhs = ids.getOperand().stripParens())
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or
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exists(CompoundAssignStmt ca | write.isAdditional(ca, "compound-rhs") |
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lhs = ca.getLhs().stripParens()
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)
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or
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exists(FuncDef fd, int idx |
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write.isAdditional(fd.getBody(), "param-init:" + idx.toString()) and
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lhs = fd.getParameter(idx).getDeclaration()
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@@ -1375,8 +1375,7 @@
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| exprs.go:51:3:51:5 | res | exprs.go:51:3:51:5 | After res |
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| exprs.go:51:3:51:14 | ... += ... | exprs.go:51:3:51:5 | Before res |
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| exprs.go:51:3:51:14 | After ... += ... | exprs.go:50:31:52:2 | After block statement |
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| exprs.go:51:3:51:14 | assign:0 ... += ... | exprs.go:51:3:51:14 | After ... += ... |
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| exprs.go:51:3:51:14 | compound-rhs ... += ... | exprs.go:51:3:51:14 | assign:0 ... += ... |
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| exprs.go:51:3:51:14 | compound-rhs ... += ... | exprs.go:51:3:51:14 | After ... += ... |
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| exprs.go:51:10:51:11 | After xs | exprs.go:51:13:51:13 | Before i |
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| exprs.go:51:10:51:11 | Before xs | exprs.go:51:10:51:11 | xs |
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| exprs.go:51:10:51:11 | xs | exprs.go:51:10:51:11 | After xs |
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@@ -2013,8 +2012,7 @@
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| main.go:17:3:17:3 | y | main.go:17:3:17:3 | After y |
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| main.go:17:3:17:9 | ... += ... | main.go:17:3:17:3 | Before y |
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| main.go:17:3:17:9 | After ... += ... | main.go:16:12:18:2 | After block statement |
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| main.go:17:3:17:9 | assign:0 ... += ... | main.go:17:3:17:9 | After ... += ... |
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| main.go:17:3:17:9 | compound-rhs ... += ... | main.go:17:3:17:9 | assign:0 ... += ... |
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| main.go:17:3:17:9 | compound-rhs ... += ... | main.go:17:3:17:9 | After ... += ... |
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| main.go:17:8:17:9 | 19 | main.go:17:8:17:9 | After 19 |
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| main.go:17:8:17:9 | After 19 | main.go:17:3:17:9 | compound-rhs ... += ... |
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| main.go:17:8:17:9 | Before 19 | main.go:17:8:17:9 | 19 |
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@@ -2131,8 +2129,7 @@
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| main.go:35:2:35:3 | star expression | main.go:35:2:35:3 | After star expression |
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| main.go:35:2:35:9 | ... += ... | main.go:35:2:35:3 | Before star expression |
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| main.go:35:2:35:9 | After ... += ... | main.go:34:19:36:1 | After block statement |
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| main.go:35:2:35:9 | assign:0 ... += ... | main.go:35:2:35:9 | After ... += ... |
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| main.go:35:2:35:9 | compound-rhs ... += ... | main.go:35:2:35:9 | assign:0 ... += ... |
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| main.go:35:2:35:9 | compound-rhs ... += ... | main.go:35:2:35:9 | After ... += ... |
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| main.go:35:3:35:3 | After x | main.go:35:2:35:3 | star expression |
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| main.go:35:3:35:3 | Before x | main.go:35:3:35:3 | x |
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| main.go:35:3:35:3 | x | main.go:35:3:35:3 | After x |
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@@ -2968,8 +2965,7 @@
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| stmts5.go:8:2:8:7 | selection of val | stmts5.go:8:2:8:7 | After selection of val |
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| stmts5.go:8:2:8:16 | ... += ... | stmts5.go:8:2:8:7 | Before selection of val |
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| stmts5.go:8:2:8:16 | After ... += ... | stmts5.go:7:33:9:1 | After block statement |
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| stmts5.go:8:2:8:16 | assign:0 ... += ... | stmts5.go:8:2:8:16 | After ... += ... |
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| stmts5.go:8:2:8:16 | compound-rhs ... += ... | stmts5.go:8:2:8:16 | assign:0 ... += ... |
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| stmts5.go:8:2:8:16 | compound-rhs ... += ... | stmts5.go:8:2:8:16 | After ... += ... |
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| stmts5.go:8:12:8:16 | After other | stmts5.go:8:2:8:16 | compound-rhs ... += ... |
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| stmts5.go:8:12:8:16 | Before other | stmts5.go:8:12:8:16 | other |
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| stmts5.go:8:12:8:16 | other | stmts5.go:8:12:8:16 | After other |
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@@ -1,6 +1,6 @@
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| main.go:13:6:13:10 | assign:0 value declaration specifier | main.go:13:6:13:6 | x | main.go:13:6:13:10 | zero-init:0 value declaration specifier |
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| main.go:14:2:14:8 | assign:0 ... := ... | main.go:14:2:14:2 | y | main.go:14:7:14:8 | 23 |
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| main.go:17:3:17:9 | assign:0 ... += ... | main.go:14:2:14:2 | y | main.go:17:3:17:9 | compound-rhs ... += ... |
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| main.go:17:3:17:9 | compound-rhs ... += ... | main.go:14:2:14:2 | y | main.go:17:3:17:9 | compound-rhs ... += ... |
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| main.go:21:3:21:7 | assign:0 ... = ... | main.go:13:6:13:6 | x | main.go:21:7:21:7 | y |
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| main.go:26:28:32:1 | param-init:0 block statement | main.go:26:10:26:10 | x | main.go:26:28:32:1 | arg:0 block statement |
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| main.go:27:2:27:13 | assign:0 ... := ... | main.go:27:2:27:2 | a | main.go:27:10:27:10 | x |
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@@ -13,13 +13,13 @@
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| testdata.go:134:3:134:17 | assign:0 ... = ... | This definition of x is never used. |
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| testdata.go:143:3:143:17 | assign:0 ... = ... | This definition of x is never used. |
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| testdata.go:164:3:164:17 | assign:0 ... = ... | This definition of x is never used. |
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| testdata.go:172:3:172:18 | assign:0 ... += ... | This definition of x is never used. |
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| testdata.go:172:3:172:18 | compound-rhs ... += ... | This definition of x is never used. |
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| testdata.go:180:3:180:5 | increment statement | This definition of x is never used. |
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| testdata.go:201:2:201:24 | assign:0 ... = ... | This definition of x is never used. |
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| testdata.go:262:2:262:16 | assign:0 ... = ... | This definition of x is never used. |
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| testdata.go:268:2:268:16 | assign:0 ... = ... | This definition of x is never used. |
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| testdata.go:309:2:309:7 | assign:0 ... /= ... | This definition of a is never used. |
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| testdata.go:321:2:321:7 | assign:0 ... %= ... | This definition of a is never used. |
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| testdata.go:309:2:309:7 | compound-rhs ... /= ... | This definition of a is never used. |
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| testdata.go:321:2:321:7 | compound-rhs ... %= ... | This definition of a is never used. |
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| testdata.go:387:3:387:17 | assign:0 ... = ... | This definition of x is never used. |
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| testdata.go:432:3:432:17 | assign:0 ... = ... | This definition of x is never used. |
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| testdata.go:434:3:434:17 | assign:0 ... = ... | This definition of x is never used. |
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