[InferAddressSpaces] NFC: For noop IntToPtr/PtrToInt pair cast to operator instead of PtrToInt

[rksharma]

Summary

Compiler crashes at an assertion while casting operands to PtrToIntInst at some cases when ptrtoint is present as an explicit operand to inttoptr. Explicit instruction operator as operand can not be casted to an Instruction.

This patch replaces cast from PtrToInst to Operator which are later checked for constant expressions.

[arsenm]

llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp

474

Can't you access the operator operand anyway and still handle constant expressions?

[rksharma]

llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp

474

Are you saying something like,

PushPtrOperand(cast<Operator>(I2P->getOperand(0))->getOperand(0));

[rksharma]

llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp

474

Yes, this will work because it does check for constant expressions inside PushPtrOperand

[arsenm]

llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp

474

Yes

[rksharma]

Updated the title, summary and the diff with casting to operator.

[hliao]

llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp

474

Yes, this will work because it does check for constant expressions inside PushPtrOperand

That original cast is unnecessary and should be removed.

[hliao]

llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp

474

Sorry, read the wrong code. LGTM

llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp

else if (ICmpInst *Cmp = dyn_cast<ICmpInst>(&I)) {
         PushPtrOperand(Cmp->getOperand(1));
       }
     } else if (auto *ASC = dyn_cast<AddrSpaceCastInst>(&I)) {
       if (!ASC->getType()->isVectorTy())
         PushPtrOperand(ASC->getPointerOperand());
     } else if (auto *I2P = dyn_cast<IntToPtrInst>(&I)) {
       if (isNoopPtrIntCastPair(cast<Operator>(I2P), *DL, TTI))
         PushPtrOperand(
-            cast<PtrToIntInst>(I2P->getOperand(0))->getPointerOperand());
+            cast<Operator>(I2P->getOperand(0))->getOperand(0));
     }
   }
 
   std::vector<WeakTrackingVH> Postorder; // The resultant postorder.
   while (!PostorderStack.empty()) {
     Value *TopVal = PostorderStack.back().getPointer();
     // If the operands of the expression on the top are already explored,
     // adds that expression to the resultant postorder.

llvm/test/Transforms/InferAddressSpaces/AMDGPU/noop-ptrint-pair.ll

 
 ; COMMON-LABEL: @noop_ptrint_pair_ce2(
 ; AMDGCN-NEXT: ret i32* addrspacecast (i32 addrspace(1)* @g to i32*)
 ; NOTTI-NEXT: ret i32* inttoptr (i64 ptrtoint (i32 addrspace(1)* @g to i64) to i32*)
 define i32* @noop_ptrint_pair_ce2() {
   ret i32* inttoptr (i64 ptrtoint (i32 addrspace(1)* @g to i64) to i32*)
 }
 
+; COMMON-LABEL: @noop_ptrint_pair_ce3(
+; AMDGCN-NEXT: %i = inttoptr i64 ptrtoint (i32 addrspace(1)* @g to i64) to i32*
+; AMDGCN-NEXT: ret void
+; NOTTI-NEXT: %i = inttoptr i64 ptrtoint (i32 addrspace(1)* @g to i64) to i32*
+; NOTTI-NEXT: ret void
+define void @noop_ptrint_pair_ce3() {
+  %i = inttoptr i64 ptrtoint (i32 addrspace(1)* @g to i64) to i32*
+  ret void
+}
+
 ; COMMON-LABEL: @non_noop_ptrint_pair_ce(
 ; AMDGCN-NEXT: store i32 0, i32* inttoptr (i64 ptrtoint (i32 addrspace(3)* @l to i64) to i32*)
 ; AMDGCN-NEXT: ret void
 ; NOTTI-NEXT: store i32 0, i32* inttoptr (i64 ptrtoint (i32 addrspace(3)* @l to i64) to i32*)
 ; NOTTI-NEXT: ret void
 define void @non_noop_ptrint_pair_ce() {
   store i32 0, i32* inttoptr (i64 ptrtoint (i32 addrspace(3)* @l to i64) to i32*)
   ret void