[llvm] [GlobalIsel] Combine selects with constants (PR #76089)

[Thorsten Schütt via llvm-commits]

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@@ -6352,16 +6352,22 @@ bool CombinerHelper::tryFoldSelectOfConstants(GSelect *Select,
   LLT CondTy = MRI.getType(Select->getCondReg());
   LLT TrueTy = MRI.getType(Select->getTrueReg());
 
-  // Either both are scalars or both are vectors.
-  std::optional<APInt> TrueOpt = getConstantOrConstantSplatVector(True);
-  std::optional<APInt> FalseOpt = getConstantOrConstantSplatVector(False);
+  // Only do this before legalization to avoid conflicting with target-specific
+  // transforms in the other direction.
+  if (CondTy != LLT::scalar(1))
+    return false;
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tschuett wrote:

The text was inspired by the DAG combiner. I updated it.

https://github.com/llvm/llvm-project/pull/76089