[X86] combinePTESTCC - canonicalize constants to the RHS if the PTEST/TESTP node just uses the ZF flag #165601
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…/TESTP node just uses the ZF flag If we're just comparing against zero then move the constant to the RHS to reduce duplicated folds. Noticed while triaging llvm#156233
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@llvm/pr-subscribers-backend-x86 Author: Simon Pilgrim (RKSimon) ChangesIf we're just comparing against zero then move the constant to the RHS to reduce duplicated folds. Noticed while triaging #156233 Full diff: https://github.com/llvm/llvm-project/pull/165601.diff 1 Files Affected:
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 89b42da9a40f0..624cff24ddf03 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -48787,6 +48787,11 @@ static SDValue combinePTESTCC(SDValue EFLAGS, X86::CondCode &CC,
}
if (CC == X86::COND_E || CC == X86::COND_NE) {
+ // Canonicalize constant to RHS if we're just using ZF.
+ if (Op0 != Op1 && DAG.isConstantIntBuildVectorOrConstantInt(Op0) &&
+ !DAG.isConstantIntBuildVectorOrConstantInt(Op1))
+ return DAG.getNode(EFLAGS.getOpcode(), SDLoc(EFLAGS), VT, Op1, Op0);
+
// TESTZ(X,~Y) == TESTC(Y,X)
if (SDValue NotOp1 = IsNOT(Op1, DAG)) {
CC = (CC == X86::COND_E ? X86::COND_B : X86::COND_AE);
@@ -48850,10 +48855,6 @@ static SDValue combinePTESTCC(SDValue EFLAGS, X86::CondCode &CC,
}
}
- // TESTZ(-1,X) == TESTZ(X,X)
- if (ISD::isBuildVectorAllOnes(Op0.getNode()))
- return DAG.getNode(EFLAGS.getOpcode(), SDLoc(EFLAGS), VT, Op1, Op1);
-
// TESTZ(X,-1) == TESTZ(X,X)
if (ISD::isBuildVectorAllOnes(Op1.getNode()))
return DAG.getNode(EFLAGS.getOpcode(), SDLoc(EFLAGS), VT, Op0, Op0);
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Collaborator
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/206/builds/8145 Here is the relevant piece of the build log for the reference |
Collaborator
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/186/builds/13558 Here is the relevant piece of the build log for the reference |
aokblast
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…/TESTP node just uses the ZF flag (llvm#165601) If we're just comparing against zero then move the constant to the RHS to reduce duplicated folds. Noticed while triaging llvm#156233
DEBADRIBASAK
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Nov 3, 2025
…/TESTP node just uses the ZF flag (llvm#165601) If we're just comparing against zero then move the constant to the RHS to reduce duplicated folds. Noticed while triaging llvm#156233
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If we're just comparing against zero then move the constant to the RHS to reduce duplicated folds.
Noticed while triaging #156233