nordic-dev.net/rust
nordic-dev.net/rust
2
0
Fork 0
mirror of https://github.com/rust-lang/rust.git synced 2024-11-22 23:04:33 +00:00
Code Issues Packages Projects Releases Wiki Activity

Optimize large array creation in const-eval

Browse Source 
This changes repeated memcpy's to a memset for the case that we're
propagating a single byte into a region of memory.
This commit is contained in:
Mark Rousskov 2024-01-17 13:53:25 -05:00
parent c58a5da7d4
commit e68f3039d4
1 changed files with 19 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
compiler/rustc_const_eval/src/interpret/memory.rs
View File

@ -1209,21 +1209,28 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
throw_ub_custom!(fluent::const_eval_copy_nonoverlapping_overlapping);
}
}
}
for i in 0..num_copies {
ptr::copy(
src_bytes,
dest_bytes.add((size * i).bytes_usize()), // `Size` multiplication
size.bytes_usize(),
);
let size_in_bytes = size.bytes_usize();
// For particularly large arrays (where this is perf-sensitive) it's common that
// we're writing a single byte repeatedly. So, optimize that case to a memset.
if size_in_bytes == 1 && num_copies >= 1 {
// SAFETY: `src_bytes` would be read from anyway by copies below (num_copies >= 1).
// Since size_in_bytes = 1, then the `init.no_bytes_init()` check above guarantees
// that this read at type `u8` is OK -- it must be an initialized byte.
let value = *src_bytes;
dest_bytes.write_bytes(value, (size * num_copies).bytes_usize());
} else if src_alloc_id == dest_alloc_id {
let mut dest_ptr = dest_bytes;
for _ in 0..num_copies {
ptr::copy(src_bytes, dest_ptr, size_in_bytes);
dest_ptr = dest_ptr.add(size_in_bytes);
}
} else {
for i in 0..num_copies {
ptr::copy_nonoverlapping(
src_bytes,
dest_bytes.add((size * i).bytes_usize()), // `Size` multiplication
size.bytes_usize(),
);
let mut dest_ptr = dest_bytes;
for _ in 0..num_copies {
ptr::copy_nonoverlapping(src_bytes, dest_ptr, size_in_bytes);
dest_ptr = dest_ptr.add(size_in_bytes);
}
}
}