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Auto merge of #134117 - DianQK:gep-i8, r=oli-obk

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Modifies the index instruction from `gep [0 x %Type]` to `gep %Type`

Fixes #133979.

This PR modifies the index instruction from `gep [0 x %Type]` to `gep %Type`, which is the same with pointer offset calculation.

This will help LLVM calculate various formats of GEP instructions. According to [[RFC] Replacing getelementptr with ptradd](https://discourse.llvm.org/t/rfc-replacing-getelementptr-with-ptradd/68699), we ultimately aim to canonicalize everything to `gep i8`. Based on the results from https://github.com/rust-lang/rust/pull/134117#issuecomment-2531717076, I think we still need to investigate some missing optimizations, so this PR is just a small step forward.

r? compiler
This commit is contained in:
bors 2024-12-15 13:50:38 +00:00
commit a611773d80
3 changed files with 60 additions and 4 deletions
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5
compiler/rustc_codegen_ssa/src/mir/place.rs
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@ -422,10 +422,7 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
layout.size
};
let llval = bx.inbounds_gep(bx.cx().backend_type(self.layout), self.val.llval, &[
bx.cx().const_usize(0),
llindex,
]);
let llval = bx.inbounds_gep(bx.cx().backend_type(layout), self.val.llval, &[llindex]);
let align = self.val.align.restrict_for_offset(offset);
PlaceValue::new_sized(llval, align).with_type(layout)
}