[InstCombine] fix crash due to ignored addrspacecast

[JeffBezanson]

Summary

Part of the InstCombine code for simplifying GEPs looks through
addrspacecasts. However, this was done by updating a variable
also used by the next transformation, for marking GEPs as
inbounds. This led to replacing a GEP with a similar instruction
in a different addrspace, which caused an assertion failure in RAUW.

This caused julia issue https://github.com/JuliaLang/julia/issues/27055

[arsenm]

test/Transforms/InstCombine/gep-addrspace.ll

45 ↗

(On Diff #146210)

Seems like more should be checked, like the GEP from the broken transform (as well as the source/dest address spaces)

[JeffBezanson]

Add more checks

[arsenm]

LGTM

llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp

if (HasZeroPointerIndex) {
         }
       }
     }
   }
 
   // addrspacecast between types is canonicalized as a bitcast, then an
   // addrspacecast. To take advantage of the below bitcast + struct GEP, look
   // through the addrspacecast.
+  Value *ASCStrippedPtrOp = PtrOp;
   if (auto *ASC = dyn_cast<AddrSpaceCastInst>(PtrOp)) {
     //   X = bitcast A addrspace(1)* to B addrspace(1)*
     //   Y = addrspacecast A addrspace(1)* to B addrspace(2)*
     //   Z = gep Y, <...constant indices...>
     // Into an addrspacecasted GEP of the struct.
     if (auto *BC = dyn_cast<BitCastInst>(ASC->getOperand(0)))
-      PtrOp = BC;
+      ASCStrippedPtrOp = BC;
   }
 
-  if (auto *BCI = dyn_cast<BitCastInst>(PtrOp)) {
+  if (auto *BCI = dyn_cast<BitCastInst>(ASCStrippedPtrOp)) {
     Value *SrcOp = BCI->getOperand(0);
     PointerType *SrcType = cast<PointerType>(BCI->getSrcTy());
     Type *SrcEltType = SrcType->getElementType();
 
     // GEP directly using the source operand if this GEP is accessing an element
     // of a bitcasted pointer to vector or array of the same dimensions:
     // gep (bitcast <c x ty>* X to [c x ty]*), Y, Z --> gep X, Y, Z
     // gep (bitcast [c x ty]* X to <c x ty>*), Y, Z --> gep X, Y, Z

llvm/trunk/test/Transforms/InstCombine/gep-addrspace.ll

 ; CHECK: addrspacecast float addrspace(3)* %{{[0-9]+}} to float*
   %1 = getelementptr [0 x float], [0 x float]* addrspacecast (float addrspace(3)* @scalar to [0 x float]*), i64 0, i64 %i
 ; CHECK: addrspacecast float addrspace(3)* %{{[0-9]+}} to float*
   store float* %0, float** %out0, align 4
   store float* %1, float** %out1, align 4
   ret void
 }
 
+declare void @escape_alloca(i16*)
+
+; check that addrspacecast is not ignored (leading to an assertion failure)
+; when trying to mark a GEP as inbounds
+define { i8, i8 } @inbounds_after_addrspacecast() {
+top:
+; CHECK-LABEL: @inbounds_after_addrspacecast
+  %0 = alloca i16, align 2
+  call void @escape_alloca(i16* %0)
+  %tmpcast = bitcast i16* %0 to [2 x i8]*
+; CHECK: addrspacecast [2 x i8]* %tmpcast to [2 x i8] addrspace(11)*
+  %1 = addrspacecast [2 x i8]* %tmpcast to [2 x i8] addrspace(11)*
+; CHECK: getelementptr [2 x i8], [2 x i8] addrspace(11)* %1, i64 0, i64 1
+  %2 = getelementptr [2 x i8], [2 x i8] addrspace(11)* %1, i64 0, i64 1
+; CHECK: addrspace(11)
+  %3 = load i8, i8 addrspace(11)* %2, align 1
+  %.fca.1.insert = insertvalue { i8, i8 } zeroinitializer, i8 %3, 1
+  ret { i8, i8 } %.fca.1.insert
+}