[llvm] [EarlyCSE] Compare GEP instructions based on offset (PR #65875)

[Nikita Popov via llvm-commits]

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@@ -1561,6 +1646,31 @@ bool EarlyCSE::processNode(DomTreeNode *Node) {
       continue;
     }
 
+    // Compare GEP instructions based on offset.
+    if (GEPValue::canHandle(&Inst)) {
+      auto *GEP = cast<GetElementPtrInst>(&Inst);
+      APInt Offset = APInt(SQ.DL.getIndexTypeSizeInBits(GEP->getType()), 0);
+      GEPValue GEPVal(GEP, GEP->accumulateConstantOffset(SQ.DL, Offset)
+                               ? Offset.tryZExtValue()
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nikic wrote:

I think the offset should be `int64_t` and use `trySExtValue()` here. GEP offsets are signed. (Mainly for clarify, I think it will not make a functional difference?)

https://github.com/llvm/llvm-project/pull/65875