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Use size_of_val instead of manual calculation #109287

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Mar 18, 2023
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Use size_of_val instead of manual calculation #109287

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2 changes: 1 addition & 1 deletion compiler/rustc_codegen_ssa/src/glue.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -46,7 +46,7 @@ pub fn size_and_align_of_dst<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
// NOTE: ideally, we want the effects of both `unchecked_smul` and `unchecked_umul`
// (resulting in `mul nsw nuw` in LLVM IR), since we know that the multiplication
// cannot signed wrap, and that both operands are non-negative. But at the time of writing,
// `BuilderMethods` can't do this, and it doesn't seem to enable any further optimizations.
// the `LLVM-C` binding can't do this, and it doesn't seem to enable any further optimizations.
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Just to keep someone else from going "well adding it to our trait sounds easy" -- the actual hard part is adding it to

https://github.com/llvm/llvm-project/blob/681d5eecf7b32748763e5a8f56f7c334d8d6901e/llvm/include/llvm-c/Core.h#L3873-L3876

bx.unchecked_smul(info.unwrap(), bx.const_usize(unit.size.bytes())),
bx.const_usize(unit.align.abi.bytes()),
)
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2 changes: 1 addition & 1 deletion library/core/src/hash/mod.rs
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Expand Up @@ -834,7 +834,7 @@ mod impls {

#[inline]
fn hash_slice<H: ~const Hasher>(data: &[$ty], state: &mut H) {
let newlen = data.len() * mem::size_of::<$ty>();
let newlen = mem::size_of_val(data);
let ptr = data.as_ptr() as *const u8;
// SAFETY: `ptr` is valid and aligned, as this macro is only used
// for numeric primitives which have no padding. The new slice only
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