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Rollup merge of #139644 - yotamofek:pr/mir_transform/instsimplify/simplify_primitive_clone, r=compiler-errors

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Micro-optimize `InstSimplify`'s `simplify_primitive_clone`

r? ````@compiler-errors```` , since you already did #139411 and got randomly selected for #139638 (feel free to reassign!)

Another one similar in spirit to #139411, but this time for `simplify_primitive_clone`, which is doing a bit of redundant work. Might not show up in benches, but probably worth micro-optimizing since the transformation is run even for debug builds.

See inline comments for my reasoning for making these changes.
This commit is contained in:
Jacob Pratt 2025-04-13 17:37:54 -04:00 • committed by GitHub
commit 388d612765
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1 changed files with 8 additions and 17 deletions
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25
compiler/rustc_mir_transform/src/instsimplify.rs
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@ -10,7 +10,6 @@ use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt, layout};
use rustc_span::{DUMMY_SP, Symbol, sym};
use crate::simplify::simplify_duplicate_switch_targets;
use crate::take_array;
pub(super) enum InstSimplify {
BeforeInline,
@ -214,7 +213,9 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
terminator: &mut Terminator<'tcx>,
statements: &mut Vec<Statement<'tcx>>,
) {
let TerminatorKind::Call { func, args, destination, target, .. } = &mut terminator.kind
let TerminatorKind::Call {
func, args, destination, target: Some(destination_block), ..
} = &terminator.kind
else {
return;
};
@ -222,15 +223,8 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
// It's definitely not a clone if there are multiple arguments
let [arg] = &args[..] else { return };
let Some(destination_block) = *target else { return };
// Only bother looking more if it's easy to know what we're calling
let Some((fn_def_id, fn_args)) = func.const_fn_def() else { return };
// Clone needs one arg, so we can cheaply rule out other stuff
if fn_args.len() != 1 {
return;
}
let Some((fn_def_id, ..)) = func.const_fn_def() else { return };
// These types are easily available from locals, so check that before
// doing DefId lookups to figure out what we're actually calling.
@ -238,15 +232,12 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
let ty::Ref(_region, inner_ty, Mutability::Not) = *arg_ty.kind() else { return };
if !inner_ty.is_trivially_pure_clone_copy() {
if !self.tcx.is_lang_item(fn_def_id, LangItem::CloneFn)
|| !inner_ty.is_trivially_pure_clone_copy()
{
return;
}
if !self.tcx.is_lang_item(fn_def_id, LangItem::CloneFn) {
return;
}
let Ok([arg]) = take_array(args) else { return };
let Some(arg_place) = arg.node.place() else { return };
statements.push(Statement {
@ -258,7 +249,7 @@ impl<'tcx> InstSimplifyContext<'_, 'tcx> {
)),
))),
});
terminator.kind = TerminatorKind::Goto { target: destination_block };
terminator.kind = TerminatorKind::Goto { target: *destination_block };
}
fn simplify_nounwind_call(&self, terminator: &mut Terminator<'tcx>) {