[PATCH] D110245: [ConstantFolding] Fold ptrtoint(gep i8 null, x) -> x
Alexander Richardson via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Sep 23 02:25:14 PDT 2021
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
}
```
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D110245/new/
https://reviews.llvm.org/D110245
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