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| author | bors <bors@rust-lang.org> | 2022-12-18 22:01:39 +0000 |
|---|---|---|
| committer | bors <bors@rust-lang.org> | 2022-12-18 22:01:39 +0000 |
| commit | 2b094b1ede1cb04095a3210eb2f40f398d4a832a (patch) | |
| tree | ec3775f15dcec456448837bfa51911bc1af0c194 /compiler/rustc_codegen_ssa | |
| parent | d0dc9efff14ac0a1eeceffd1e605e37eeb8362a0 (diff) | |
| parent | e01d944c6c33a76cdbd1a257743d8c41a8203e89 (diff) | |
| download | rust-2b094b1ede1cb04095a3210eb2f40f398d4a832a.tar.gz rust-2b094b1ede1cb04095a3210eb2f40f398d4a832a.zip | |
Auto merge of #105446 - erikdesjardins:vt-size, r=nikic
Add 0..=isize::MAX range metadata to size loads from vtables This is the (much belated) size counterpart to #91569. Inspired by https://rust-lang.zulipchat.com/#narrow/stream/187780-t-compiler.2Fwg-llvm/topic/Range.20metadata.20for.20.60size_of_val.60.20and.20other.20isize.3A.3AMAX.20limits. This could help optimize layout computations based on the size of a dyn trait. Though, admittedly, adding this to vtables wouldn't be as beneficial as adding it to slice len, which is used much more often. Miri detects this UB already: https://github.com/rust-lang/rust/blob/b7cc99142ad0cfe47e2fe9f7a82eaf5b672c0573/compiler/rustc_const_eval/src/interpret/traits.rs#L119-L121 (In fact Miri goes further, [assuming a 48-bit address space on 64-bit platforms](https://github.com/rust-lang/rust/blob/9db224fc908059986c179fc6ec433944e9cfce50/compiler/rustc_abi/src/lib.rs#L312-L331), but I don't think we can assume that in an optimization.)
Diffstat (limited to 'compiler/rustc_codegen_ssa')
| -rw-r--r-- | compiler/rustc_codegen_ssa/src/glue.rs | 3 | ||||
| -rw-r--r-- | compiler/rustc_codegen_ssa/src/mir/intrinsic.rs | 12 |
2 files changed, 12 insertions, 3 deletions
diff --git a/compiler/rustc_codegen_ssa/src/glue.rs b/compiler/rustc_codegen_ssa/src/glue.rs index 6015d48deca..0f6e6032f9b 100644 --- a/compiler/rustc_codegen_ssa/src/glue.rs +++ b/compiler/rustc_codegen_ssa/src/glue.rs @@ -29,6 +29,9 @@ pub fn size_and_align_of_dst<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>( let align = meth::VirtualIndex::from_index(ty::COMMON_VTABLE_ENTRIES_ALIGN) .get_usize(bx, vtable); + // Size is always <= isize::MAX. + let size_bound = bx.data_layout().ptr_sized_integer().signed_max() as u128; + bx.range_metadata(size, WrappingRange { start: 0, end: size_bound }); // Alignment is always nonzero. bx.range_metadata(align, WrappingRange { start: 1, end: !0 }); diff --git a/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs b/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs index 215edbe02c0..a75609260ed 100644 --- a/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs +++ b/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs @@ -110,10 +110,16 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { _ => bug!(), }; let value = meth::VirtualIndex::from_index(idx).get_usize(bx, vtable); - if name == sym::vtable_align { + match name { + // Size is always <= isize::MAX. + sym::vtable_size => { + let size_bound = bx.data_layout().ptr_sized_integer().signed_max() as u128; + bx.range_metadata(value, WrappingRange { start: 0, end: size_bound }); + }, // Alignment is always nonzero. - bx.range_metadata(value, WrappingRange { start: 1, end: !0 }); - }; + sym::vtable_align => bx.range_metadata(value, WrappingRange { start: 1, end: !0 }), + _ => {} + } value } sym::pref_align_of |