[PATCH] D110245: [ConstantFolding] Fold ptrtoint(gep i8 null, x) -> x

[Alexander Richardson via Phabricator via llvm-commits]

arichardson marked an inline comment as done.
arichardson added inline comments.


================
Comment at: llvm/lib/Analysis/ConstantFolding.cpp:1365
+        APInt BaseOffset(BitWidth, 0);
+        auto *Base = cast<Constant>(
+            GEP->stripAndAccumulateConstantOffsets(DL, BaseOffset, true));
----------------
lebedev.ri wrote:
> How do you know the result is a constant?
Don't all inputs need to be constants if the GEP is a `ConstantExpr`? I couldn't think of a counter-example:

Even for globals this cast works fine:
```
@a = external addrspace(1) global i16

define i64 @nofold_ptrtoint_gep_global(i32 %x) {
  %ptr = getelementptr i16, i16 addrspace(1)* @a, i32 1
  %ret = ptrtoint i16 addrspace(1)* %ptr to i64
  ret i64 %ret
}
```


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  https://reviews.llvm.org/D110245/new/

https://reviews.llvm.org/D110245