[Local] Move OverflowTracking to Local.h, move logic to helpers (NFC) (#140403)

Move parts of the logic used by Reassociate to OverflowTracking
(mergeFlags & applyFlags) and move the definition to Local.h.

For now it just moves the NUW/NSW handling, as this matches the uses in
LICM. I'll look into the FP math handling separately, as it looks like
there's a difference between Reassociate (takes all flags from I, while
LICM takes the intersection of the flags on both instructions).

PR: https://github.com/llvm/llvm-project/pull/140403

1 files changed, 18 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 3dbd605..4d168ce 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -4362,3 +4362,21 @@ bool llvm::inferAttributesFromOthers(Function &F) {
 
   return Changed;
 }
+
+void OverflowTracking::mergeFlags(Instruction &I) {
+  if (isa<OverflowingBinaryOperator>(&I)) {
+    HasNUW &= I.hasNoUnsignedWrap();
+    HasNSW &= I.hasNoSignedWrap();
+  }
+}
+
+void OverflowTracking::applyFlags(Instruction &I) {
+  I.clearSubclassOptionalData();
+  if (I.getOpcode() == Instruction::Add ||
+      (I.getOpcode() == Instruction::Mul && AllKnownNonZero)) {
+    if (HasNUW)
+      I.setHasNoUnsignedWrap();
+    if (HasNSW && (AllKnownNonNegative || HasNUW))
+      I.setHasNoSignedWrap();
+  }
+}