[flang-commits] [clang] [flang] [llvm] [InstCombine] Canonicalize GEP source element types (PR #180745)

[Yingwei Zheng via flang-commits]

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@@ -3488,6 +3488,24 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
         BackIndices, GEP.getNoWrapFlags());
   }
 
+  // Canonicalize gep %T to gep [sizeof(%T) x i8]:
+  auto IsCanonicalType = [](Type *Ty) {
+    if (auto *AT = dyn_cast<ArrayType>(Ty))
+      Ty = AT->getElementType();
+    return Ty->isIntegerTy(8);
+  };
+  if (Indices.size() == 1 && !IsCanonicalType(GEPEltType)) {
+    TypeSize Scale = DL.getTypeAllocSize(GEPEltType);
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dtcxzyw wrote:

I am not sure if we should respect ABI alignment in GEP: https://godbolt.org/z/bM1zdT96h
The current canonicalization doubles the stride.
If the answer is yes, it may be problematic to strip the leading zero index of a GEP with a vector source element type.
See also https://github.com/llvm/llvm-project/pull/75448.


https://github.com/llvm/llvm-project/pull/180745