[llvm] [InstCombine] Generalize ignoreSignBitOfZero/NaN to handle more cases (PR #141015)

[Matt Arsenault via llvm-commits]

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@@ -2783,15 +2784,41 @@ static bool ignoreSignBitOfZero(Instruction &I) {
   if (!I.hasOneUse())
     return false;
   Instruction *User = I.user_back();
+  if (auto *FPOp = dyn_cast<FPMathOperator>(User)) {
+    if (FPOp->hasNoSignedZeros())
+      return true;
+  }
 
-  // fcmp treats both positive and negative zero as equal.
-  if (User->getOpcode() == Instruction::FCmp)
+  switch (User->getOpcode()) {
+  case Instruction::FPToSI:
+  case Instruction::FPToUI:
     return true;
-
-  if (auto *FPOp = dyn_cast<FPMathOperator>(User))
-    return FPOp->hasNoSignedZeros();
-
-  return false;
+  case Instruction::FCmp:
+    // fcmp treats both positive and negative zero as equal.
+    return true;
+  case Instruction::Call:
+    if (auto *II = dyn_cast<IntrinsicInst>(User)) {
+      switch (II->getIntrinsicID()) {
+      case Intrinsic::fabs:
+        return true;
+      case Intrinsic::copysign:
+        return II->getArgOperand(0) == &I;
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arsenm wrote:

Missing negative test for the wrong operand?

https://github.com/llvm/llvm-project/pull/141015