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Remove my scalar_copy_backend_type optimization attempt

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I added this back in 111999, but I no longer think it's a good idea
- It had to get scaled back to only power-of-two things to not break a bunch of targets
- LLVM seems to be getting better at memcpy removal anyway
- Introducing vector instructions has seemed to sometimes (115515) make autovectorization worse

So this removes it from the codegen crates entirely, and instead just tries to use <https://doc.rust-lang.org/nightly/nightly-rustc/rustc_codegen_ssa/traits/builder/trait.BuilderMethods.html#method.typed_place_copy> instead of direct `memcpy` so things will still use load/store for immediates.
This commit is contained in:
Scott McMurray
2024-03-29 00:00:24 -07:00
parent ff24ef91fc
commit b5376ba601
10 changed files with 60 additions and 154 deletions
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22
compiler/rustc_codegen_ssa/src/traits/builder.rs
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@@ -281,17 +281,31 @@ pub trait BuilderMethods<'a, 'tcx>:
dst: PlaceRef<'tcx, Self::Value>,
src: PlaceRef<'tcx, Self::Value>,
) {
debug_assert!(src.llextra.is_none());
debug_assert!(dst.llextra.is_none());
self.typed_place_copy_with_flags(dst, src, MemFlags::empty());
}
fn typed_place_copy_with_flags(
&mut self,
dst: PlaceRef<'tcx, Self::Value>,
src: PlaceRef<'tcx, Self::Value>,
flags: MemFlags,
) {
debug_assert!(src.llextra.is_none(), "cannot directly copy from unsized values");
debug_assert!(dst.llextra.is_none(), "cannot directly copy into unsized values");
debug_assert_eq!(dst.layout.size, src.layout.size);
if self.sess().opts.optimize == OptLevel::No && self.is_backend_immediate(dst.layout) {
// If we're not optimizing, the aliasing information from `memcpy`
// isn't useful, so just load-store the value for smaller code.
let temp = self.load_operand(src);
temp.val.store(self, dst);
temp.val.store_with_flags(self, dst, flags);
} else if flags.contains(MemFlags::NONTEMPORAL) {
// HACK(nox): This is inefficient but there is no nontemporal memcpy.
let ty = self.backend_type(dst.layout);
let val = self.load(ty, src.llval, src.align);
self.store_with_flags(val, dst.llval, dst.align, flags);
} else if !dst.layout.is_zst() {
let bytes = self.const_usize(dst.layout.size.bytes());
self.memcpy(dst.llval, dst.align, src.llval, src.align, bytes, MemFlags::empty());
self.memcpy(dst.llval, dst.align, src.llval, src.align, bytes, flags);
}
}