bjoernager/rust
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Let codegen decide when to mem::swap with immediates

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Making `libcore` decide this is silly; the backend has so much better information about when it's a good idea.

So introduce a new `typed_swap` intrinsic with a fallback body, but replace that implementation for immediates and scalar pairs.
This commit is contained in:
Scott McMurray 2024-03-15 22:09:05 -07:00
parent fd27e8745f
commit 7d537106a1
12 changed files with 270 additions and 33 deletions
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25
compiler/rustc_const_eval/src/interpret/intrinsics.rs
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@ -21,8 +21,8 @@ use rustc_span::symbol::{sym, Symbol};
use rustc_target::abi::Size;
use super::{
util::ensure_monomorphic_enough, CheckInAllocMsg, ImmTy, InterpCx, MPlaceTy, Machine, OpTy,
Pointer,
memory::MemoryKind, util::ensure_monomorphic_enough, CheckInAllocMsg, ImmTy, InterpCx,
MPlaceTy, Machine, OpTy, Pointer,
};
use crate::fluent_generated as fluent;
@ -415,6 +415,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
let result = self.raw_eq_intrinsic(&args[0], &args[1])?;
self.write_scalar(result, dest)?;
}
sym::typed_swap => {
self.typed_swap_intrinsic(&args[0], &args[1])?;
}
sym::vtable_size => {
let ptr = self.read_pointer(&args[0])?;
@ -608,6 +611,24 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
self.mem_copy(src, dst, size, nonoverlapping)
}
/// Does a *typed* swap of `*left` and `*right`.
fn typed_swap_intrinsic(
&mut self,
left: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::Provenance>,
right: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::Provenance>,
) -> InterpResult<'tcx> {
let left = self.deref_pointer(left)?;
let right = self.deref_pointer(right)?;
debug_assert_eq!(left.layout, right.layout);
let kind = MemoryKind::Stack;
let temp = self.allocate(left.layout, kind)?;
self.copy_op(&left, &temp)?;
self.copy_op(&right, &left)?;
self.copy_op(&temp, &right)?;
self.deallocate_ptr(temp.ptr(), None, kind)?;
Ok(())
}
pub(crate) fn write_bytes_intrinsic(
&mut self,
dst: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::Provenance>,