[llvm] Decompose gep of complex type struct to its element type (PR #107848)

[via llvm-commits]

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@@ -2827,13 +2827,16 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
       bool NSW = GEPOp->hasNoUnsignedSignedWrap();
       bool NUW = GEPOp->hasNoUnsignedWrap();
       // We'll let instcombine(mul) convert this to a shl if possible.
-      auto IntTy = SExtI->getOperand(0)->getType();
-      Value *Offset =
-          Builder.CreateMul(SExtI->getOperand(0), ConstantInt::get(IntTy, 2),
-                            SExtI->getName() + ".scale", NUW, NSW);
-      return replaceInstUsesWith(
-          GEP, Builder.CreateGEP(GepResElTy->getStructElementType(0), PtrOp,
-                                 Offset, "", GEP.getNoWrapFlags()));
+      unsigned EleTypeBytes =
+          GepResElTy->getStructElementType(0)->getScalarSizeInBits() / 8;
+      if (EleTypeBytes > 0) {
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goldsteinn wrote:

Missing test with `{ i1, i1 }`?

https://github.com/llvm/llvm-project/pull/107848