[llvm] a7edc95 - [IR] Optimize stripAndAccumulateConstantOffsets() for common case (NFC)

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2025-07-23T12:19:50+02:00
New Revision: a7edc95c799c46665ecf4465a4dc7ff4bee3ced0

URL: https://github.com/llvm/llvm-project/commit/a7edc95c799c46665ecf4465a4dc7ff4bee3ced0
DIFF: https://github.com/llvm/llvm-project/commit/a7edc95c799c46665ecf4465a4dc7ff4bee3ced0.diff

LOG: [IR] Optimize stripAndAccumulateConstantOffsets() for common case (NFC)

For the common case where we don't have bit width changing address
space casts, we can directly call accumulateConstantOffset() on the
original Offset. Skip the bit width reconciliation logic in that
case.

Added: 
    

Modified: 
    llvm/lib/IR/Value.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/IR/Value.cpp b/llvm/lib/IR/Value.cpp
index 5928c89029b87..129ca4a57de5a 100644
--- a/llvm/lib/IR/Value.cpp
+++ b/llvm/lib/IR/Value.cpp
@@ -747,28 +747,34 @@ const Value *Value::stripAndAccumulateConstantOffsets(
       // means when we construct GEPOffset, we need to use the size
       // of GEP's pointer type rather than the size of the original
       // pointer type.
-      APInt GEPOffset(DL.getIndexTypeSizeInBits(V->getType()), 0);
-      if (!GEP->accumulateConstantOffset(DL, GEPOffset, ExternalAnalysis))
-        return V;
-
-      // Stop traversal if the pointer offset wouldn't fit in the bit-width
-      // provided by the Offset argument. This can happen due to AddrSpaceCast
-      // stripping.
-      if (GEPOffset.getSignificantBits() > BitWidth)
-        return V;
-
-      // External Analysis can return a result higher/lower than the value
-      // represents. We need to detect overflow/underflow.
-      APInt GEPOffsetST = GEPOffset.sextOrTrunc(BitWidth);
-      if (!ExternalAnalysis) {
-        Offset += GEPOffsetST;
+      unsigned CurBitWidth = DL.getIndexTypeSizeInBits(V->getType());
+      if (CurBitWidth == BitWidth) {
+        if (!GEP->accumulateConstantOffset(DL, Offset, ExternalAnalysis))
+          return V;
       } else {
-        bool Overflow = false;
-        APInt OldOffset = Offset;
-        Offset = Offset.sadd_ov(GEPOffsetST, Overflow);
-        if (Overflow) {
-          Offset = OldOffset;
+        APInt GEPOffset(CurBitWidth, 0);
+        if (!GEP->accumulateConstantOffset(DL, GEPOffset, ExternalAnalysis))
+          return V;
+
+        // Stop traversal if the pointer offset wouldn't fit in the bit-width
+        // provided by the Offset argument. This can happen due to AddrSpaceCast
+        // stripping.
+        if (GEPOffset.getSignificantBits() > BitWidth)
           return V;
+
+        // External Analysis can return a result higher/lower than the value
+        // represents. We need to detect overflow/underflow.
+        APInt GEPOffsetST = GEPOffset.sextOrTrunc(BitWidth);
+        if (!ExternalAnalysis) {
+          Offset += GEPOffsetST;
+        } else {
+          bool Overflow = false;
+          APInt OldOffset = Offset;
+          Offset = Offset.sadd_ov(GEPOffsetST, Overflow);
+          if (Overflow) {
+            Offset = OldOffset;
+            return V;
+          }
         }
       }
       V = GEP->getPointerOperand();