[llvm] [ConstantFolding] Support ptrtoaddr in cast folds (PR #162480)

[Hongyu Chen via llvm-commits]

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@@ -1495,17 +1495,17 @@ Constant *llvm::ConstantFoldCastOperand(unsigned Opcode, Constant *C,
   default:
     llvm_unreachable("Missing case");
   case Instruction::PtrToAddr:
-    // TODO: Add some of the ptrtoint folds here as well.
-    break;
   case Instruction::PtrToInt:
     if (auto *CE = dyn_cast<ConstantExpr>(C)) {
       Constant *FoldedValue = nullptr;
       // If the input is a inttoptr, eliminate the pair.  This requires knowing
       // the width of a pointer, so it can't be done in ConstantExpr::getCast.
       if (CE->getOpcode() == Instruction::IntToPtr) {
-        // zext/trunc the inttoptr to pointer size.
-        FoldedValue = ConstantFoldIntegerCast(CE->getOperand(0),
-                                              DL.getIntPtrType(CE->getType()),
+        // zext/trunc the inttoptr to pointer/address size.
+        Type *MidTy = Opcode == Instruction::PtrToInt
+                          ? DL.getAddressType(CE->getType())
+                          : DL.getIntPtrType(CE->getType());
+        FoldedValue = ConstantFoldIntegerCast(CE->getOperand(0), MidTy,
                                               /*IsSigned=*/false, DL);
       } else if (auto *GEP = dyn_cast<GEPOperator>(CE)) {
         // If we have GEP, we can perform the following folds:
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XChy wrote:

Replace the `ptrtoint` in the below comments with `ptrtoint/ptrtoaddr`.

https://github.com/llvm/llvm-project/pull/162480