bjoernager/rust
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Auto merge of #105323 - cjgillot:simplify-const-prop, r=davidtwco

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Perform SimplifyLocals before ConstProp.

MIR before `ConstProp` may have a lot of dead writes, this makes `ConstProp` do unnecessary work.

r? `@ghost`
This commit is contained in:
bors 2023-01-07 16:13:18 +00:00
commit b1691f6413
81 changed files with 379 additions and 512 deletions
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2
compiler/rustc_mir_transform/src/dead_store_elimination.rs
View file

@ -71,7 +71,7 @@ pub fn eliminate<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>, borrowed: &BitS
bbs[block].statements[statement_index].make_nop();
}
crate::simplify::SimplifyLocals.run_pass(tcx, body)
crate::simplify::simplify_locals(body, tcx)
}
pub struct DeadStoreElimination;

3
compiler/rustc_mir_transform/src/lib.rs
View file

@ -557,6 +557,7 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
&multiple_return_terminators::MultipleReturnTerminators,
&instcombine::InstCombine,
&separate_const_switch::SeparateConstSwitch,
&simplify::SimplifyLocals::new("before-const-prop"),
//
// FIXME(#70073): This pass is responsible for both optimization as well as some lints.
&const_prop::ConstProp,
@ -575,7 +576,7 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
&o1(remove_noop_landing_pads::RemoveNoopLandingPads),
&o1(simplify::SimplifyCfg::new("final")),
&nrvo::RenameReturnPlace,
&simplify::SimplifyLocals,
&simplify::SimplifyLocals::new("final"),
&multiple_return_terminators::MultipleReturnTerminators,
&deduplicate_blocks::DeduplicateBlocks,
// Some cleanup necessary at least for LLVM and potentially other codegen backends.

15
compiler/rustc_mir_transform/src/simplify.rs
View file

@ -379,9 +379,21 @@ fn save_unreachable_coverage(
));
}
pub struct SimplifyLocals;
pub struct SimplifyLocals {
label: String,
}
impl SimplifyLocals {
pub fn new(label: &str) -> SimplifyLocals {
SimplifyLocals { label: format!("SimplifyLocals-{}", label) }
}
}
impl<'tcx> MirPass<'tcx> for SimplifyLocals {
fn name(&self) -> &str {
&self.label
}
fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
sess.mir_opt_level() > 0
}
@ -557,6 +569,7 @@ fn remove_unused_definitions(used_locals: &mut UsedLocals, body: &mut Body<'_>)
StatementKind::SetDiscriminant { ref place, .. }
| StatementKind::Deinit(ref place) => used_locals.is_used(place.local),
StatementKind::Nop => false,
_ => true,
};