[llvm] [InstCombine] Resolve TODO: Remove one-time check if other logic operand (Y) is constant (PR #77973)

[via llvm-commits]

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@@ -368,12 +368,17 @@ static Instruction *foldShiftOfShiftedBinOp(BinaryOperator &I,
 
   // Find a matching one-use shift by constant. The fold is not valid if the sum
   // of the shift values equals or exceeds bitwidth.
-  // TODO: Remove the one-use check if the other logic operand (Y) is constant.
   Value *X, *Y;
-  auto matchFirstShift = [&](Value *V) {
+  auto matchFirstShift = [&](Value *V, Value *W) {
     APInt Threshold(Ty->getScalarSizeInBits(), Ty->getScalarSizeInBits());
-    return match(V,
-                 m_OneUse(m_BinOp(ShiftOpcode, m_Value(X), m_Constant(C0)))) &&
+    bool matchFirst;
+    if (match(W, m_ImmConstant()))
+      matchFirst = match(V, (m_BinOp(ShiftOpcode, m_Value(X), m_Constant(C0))));
+    else
+      matchFirst =
+          match(V, m_OneUse(m_BinOp(ShiftOpcode, m_Value(X), m_Constant(C0))));
+
+    return matchFirst &&
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AtariDreams wrote:

@nikic Done!

https://github.com/llvm/llvm-project/pull/77973