bjoernager/rust
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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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38
compiler/rustc_codegen_ssa/src/base.rs
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@ -12,7 +12,7 @@ use crate::mir;
use crate::mir::operand::OperandValue;
use crate::mir::place::PlaceRef;
use crate::traits::*;
use crate::{CachedModuleCodegen, CompiledModule, CrateInfo, MemFlags, ModuleCodegen, ModuleKind};
use crate::{CachedModuleCodegen, CompiledModule, CrateInfo, ModuleCodegen, ModuleKind};
use rustc_ast::expand::allocator::{global_fn_name, AllocatorKind, ALLOCATOR_METHODS};
use rustc_attr as attr;
@ -37,7 +37,7 @@ use rustc_session::config::{self, CrateType, EntryFnType, OptLevel, OutputType};
use rustc_session::Session;
use rustc_span::symbol::sym;
use rustc_span::Symbol;
use rustc_target::abi::{Align, FIRST_VARIANT};
use rustc_target::abi::FIRST_VARIANT;
use std::cmp;
use std::collections::BTreeSet;
@ -282,15 +282,7 @@ pub fn coerce_unsized_into<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
}
if src_f.layout.ty == dst_f.layout.ty {
memcpy_ty(
bx,
dst_f.llval,
dst_f.align,
src_f.llval,
src_f.align,
src_f.layout,
MemFlags::empty(),
);
bx.typed_place_copy(dst_f, src_f);
} else {
coerce_unsized_into(bx, src_f, dst_f);
}
@ -382,30 +374,6 @@ pub fn wants_new_eh_instructions(sess: &Session) -> bool {
wants_wasm_eh(sess) || wants_msvc_seh(sess)
}
pub fn memcpy_ty<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
bx: &mut Bx,
dst: Bx::Value,
dst_align: Align,
src: Bx::Value,
src_align: Align,
layout: TyAndLayout<'tcx>,
flags: MemFlags,
) {
let size = layout.size.bytes();
if size == 0 {
return;
}
if flags == MemFlags::empty()
&& let Some(bty) = bx.cx().scalar_copy_backend_type(layout)
{
let temp = bx.load(bty, src, src_align);
bx.store(temp, dst, dst_align);
} else {
bx.memcpy(dst, dst_align, src, src_align, bx.cx().const_usize(size), flags);
}
}
pub fn codegen_instance<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
cx: &'a Bx::CodegenCx,
instance: Instance<'tcx>,