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JIT: Fold SequenceEqual self-comparisons with constant length #135307

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Merged
EgorBo merged 1 commit into from
Oct 7, 2026
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JIT: Fold SequenceEqual self-comparisons with constant length #135307

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18 changes: 9 additions & 9 deletions src/coreclr/jit/assertionprop.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2655,19 +2655,19 @@ GenTree* Compiler::optVNBasedFoldExpr_Call_Memcmp(GenTreeCall* call)
CallArg* arg2 = call->gtArgs.GetUserArgByIndex(1);
CallArg* lenArg = call->gtArgs.GetUserArgByIndex(2);

// See if arguments are the same - in that case we can optimize to constant true
ValueNum arg1VN = optConservativeNormalVN(arg1->GetNode());
ValueNum arg2VN = optConservativeNormalVN(arg2->GetNode());
if ((arg1VN != ValueNumStore::NoVN) && (arg1VN == arg2VN))
{
JITDUMP("...both arguments have the same VN -> optimize to constant true.\n");
return gtWrapWithSideEffects(gtNewIconNode(1), call, GTF_ALL_EFFECT, true);
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}

ValueNum lenVN = optConservativeNormalVN(lenArg->GetNode());
size_t len;
if (!vnStore->IsVNIntegralConstant(lenVN, &len))
{
// See if arguments are the same - in that case we can optimize to constant true
ValueNum arg1VN = optConservativeNormalVN(arg1->GetNode());
ValueNum arg2VN = optConservativeNormalVN(arg2->GetNode());
if ((arg1VN != ValueNumStore::NoVN) && (arg1VN == arg2VN))
{
JITDUMP("...both arguments have the same VN -> optimize to constant true.\n");
return gtWrapWithSideEffects(gtNewIconNode(1), call, GTF_ALL_EFFECT, true);
}

JITDUMP("...length is not a constant - bail out.\n");
return nullptr;
}
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