[llvm] [X86] combinePTESTCC - fold PTESTZ(X,SIGNMASK) -> VTESTPD/PSZ(X,X) on AVX targets (PR #165676)

[Phoebe Wang via llvm-commits]

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@@ -48859,6 +48859,26 @@ static SDValue combinePTESTCC(SDValue EFLAGS, X86::CondCode &CC,
     if (ISD::isBuildVectorAllOnes(Op1.getNode()))
       return DAG.getNode(EFLAGS.getOpcode(), SDLoc(EFLAGS), VT, Op0, Op0);
 
+    // Attempt to convert PTESTZ(X,SIGNMASK) -> VTESTPD/PSZ(X,X) on AVX targets.
+    if (EFLAGS.getOpcode() == X86ISD::PTEST && Subtarget.hasAVX()) {
+      KnownBits KnownOp1 = DAG.computeKnownBits(Op1);
+      assert(KnownOp1.getBitWidth() == 64 &&
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phoebewang wrote:

SDM doesn't define element width, while `X86ptest` defines as `i32` vector. Why we check it's 64 here?

https://github.com/llvm/llvm-project/pull/165676