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Auto merge of #139411 - yotamofek:pr/mir_transform/instsimplify, r=compiler-errors

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In `simplify_repeated_aggregate`, don't test first element against itself

r? `@saethlin`
Noticed that in `InstSimplifyContext::simplify_repeated_aggregate`, we're accidentally evaluating the first element's value twice, and then comparing it with itself, instead of just checking whether the rest of the elements are equal to the first one.
This will probably save very few cycles, but since `InstSimplify` is always enabled, this might improve perf by a bit.
This commit is contained in:
bors
2025-04-06 01:45:33 +00:00
parent c2110769cd 5b596cd28b
commit 1de931283d
1 changed files with 3 additions and 3 deletions
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compiler/rustc_mir_transform/src/instsimplify.rs
+3 -3
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@@ -78,20 +78,20 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
/// GVN can also do this optimization, but GVN is only run at mir-opt-level 2 so having this in
/// InstSimplify helps unoptimized builds.
fn simplify_repeated_aggregate(&self, rvalue: &mut Rvalue<'tcx>) {
let Rvalue::Aggregate(box AggregateKind::Array(_), fields) = rvalue else {
let Rvalue::Aggregate(box AggregateKind::Array(_), fields) = &*rvalue else {
return;
};
if fields.len() < 5 {
return;
}
let first = &fields[rustc_abi::FieldIdx::ZERO];
let (first, rest) = fields[..].split_first().unwrap();
let Operand::Constant(first) = first else {
return;
};
let Ok(first_val) = first.const_.eval(self.tcx, self.typing_env, first.span) else {
return;
};
if fields.iter().all(|field| {
if rest.iter().all(|field| {
let Operand::Constant(field) = field else {
return false;
};