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Merge pull request #2844 from MathiasVP/value-numbering-performance-fix-2

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C++: Ensure that there is just one overlap for an operand in value numbering
This commit is contained in:
Dave Bartolomeo
2020-02-14 16:40:03 -07:00
committed by GitHub
parent f3c788d1e9 8b8a8cae5b
commit 867581df91
3 changed files with 42 additions and 3 deletions
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15
cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/SSAConstruction.qll
View File

@@ -96,7 +96,7 @@ private module Cached {
}
cached
Instruction getMemoryOperandDefinition(
private Instruction getMemoryOperandDefinition0(
Instruction instruction, MemoryOperandTag tag, Overlap overlap
) {
exists(OldInstruction oldInstruction, OldIR::NonPhiMemoryOperand oldOperand |
@@ -142,6 +142,19 @@ private module Cached {
overlap instanceof MustExactlyOverlap
}
cached
Instruction getMemoryOperandDefinition(
Instruction instruction, MemoryOperandTag tag, Overlap overlap
) {
// getMemoryOperandDefinition0 currently has a bug where it can match with multiple overlaps.
// This predicate ensures that the chosen overlap is the most conservative if there's any doubt.
result = getMemoryOperandDefinition0(instruction, tag, overlap) and
not (
overlap instanceof MustExactlyOverlap and
exists(MustTotallyOverlap o | exists(getMemoryOperandDefinition0(instruction, tag, o)))
)
}
/**
* Holds if `instr` is part of a cycle in the operand graph that doesn't go
* through a phi instruction and therefore should be impossible.

15
cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/SSAConstruction.qll
View File

@@ -96,7 +96,7 @@ private module Cached {
}
cached
Instruction getMemoryOperandDefinition(
private Instruction getMemoryOperandDefinition0(
Instruction instruction, MemoryOperandTag tag, Overlap overlap
) {
exists(OldInstruction oldInstruction, OldIR::NonPhiMemoryOperand oldOperand |
@@ -142,6 +142,19 @@ private module Cached {
overlap instanceof MustExactlyOverlap
}
cached
Instruction getMemoryOperandDefinition(
Instruction instruction, MemoryOperandTag tag, Overlap overlap
) {
// getMemoryOperandDefinition0 currently has a bug where it can match with multiple overlaps.
// This predicate ensures that the chosen overlap is the most conservative if there's any doubt.
result = getMemoryOperandDefinition0(instruction, tag, overlap) and
not (
overlap instanceof MustExactlyOverlap and
exists(MustTotallyOverlap o | exists(getMemoryOperandDefinition0(instruction, tag, o)))
)
}
/**
* Holds if `instr` is part of a cycle in the operand graph that doesn't go
* through a phi instruction and therefore should be impossible.