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JIT: Don't fold NEG(NEG(X)) to X when NEG(x) is a CSE candidate #57478

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Merged
EgorBo merged 4 commits into from
Aug 17, 2021
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JIT: Don't fold NEG(NEG(X)) to X when NEG(x) is a CSE candidate #57478

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83b8dd9
Don't do "neg(neg(x)) to x" where neg(x) is a cse candidate
EgorBo Aug 16, 2021
3312937
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EgorBo Aug 16, 2021
23efc52
Add Kunal's test
EgorBo Aug 16, 2021
011d1da
Merge branch 'main' of https://github.com/dotnet/runtime into fix-min…
EgorBo Aug 17, 2021
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Don't do "neg(neg(x)) to x" where neg(x) is a cse candidate
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@EgorBo
EgorBo committed Aug 16, 2021
commit 83b8dd95f806ae1a735917c648327952960cfe22
9 changes: 6 additions & 3 deletions src/coreclr/jit/morph.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -13117,10 +13117,13 @@ GenTree* Compiler::fgMorphSmpOp(GenTree* tree, MorphAddrContext* mac)
// Consider for example the following expression: NEG(NEG(OP)), where the top-level
// NEG is a CSE candidate. Were we to morph this to just OP, CSE would fail to find
// the original NEG in the statement.
if (op1->OperIs(oper) && opts.OptimizationEnabled() && !gtIsActiveCSE_Candidate(tree))
if (op1->OperIs(oper) && opts.OptimizationEnabled() && !gtIsActiveCSE_Candidate(tree) &&
!gtIsActiveCSE_Candidate(op1))
{
GenTree* child = op1->AsOp()->gtGetOp1();
return child;
GenTree* op1op1 = op1->gtGetOp1();
DEBUG_DESTROY_NODE(tree);
DEBUG_DESTROY_NODE(op1);
return op1op1;
}

// Distribute negation over simple multiplication/division expressions
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