diff options
| -rw-r--r-- | compiler/rustc_mir/src/transform/instcombine.rs | 27 | ||||
| -rw-r--r-- | compiler/rustc_mir/src/transform/mod.rs | 2 | ||||
| -rw-r--r-- | compiler/rustc_mir/src/transform/remove_zsts.rs | 49 |
3 files changed, 52 insertions, 26 deletions
diff --git a/compiler/rustc_mir/src/transform/instcombine.rs b/compiler/rustc_mir/src/transform/instcombine.rs index 5ac2ff1fc9a..bad82fe893e 100644 --- a/compiler/rustc_mir/src/transform/instcombine.rs +++ b/compiler/rustc_mir/src/transform/instcombine.rs @@ -12,12 +12,10 @@ pub struct InstCombine; impl<'tcx> MirPass<'tcx> for InstCombine { fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { - let param_env = tcx.param_env(body.source.def_id()); let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut(); - let ctx = InstCombineContext { tcx, local_decls, param_env }; + let ctx = InstCombineContext { tcx, local_decls }; for block in basic_blocks.iter_mut() { for statement in block.statements.iter_mut() { - ctx.combine_zst(&statement.source_info, &mut statement.kind); match statement.kind { StatementKind::Assign(box (_place, ref mut rvalue)) => { ctx.combine_bool_cmp(&statement.source_info, rvalue); @@ -34,7 +32,6 @@ impl<'tcx> MirPass<'tcx> for InstCombine { struct InstCombineContext<'tcx, 'a> { tcx: TyCtxt<'tcx>, local_decls: &'a LocalDecls<'tcx>, - param_env: ty::ParamEnv<'tcx>, } impl<'tcx, 'a> InstCombineContext<'tcx, 'a> { @@ -44,28 +41,6 @@ impl<'tcx, 'a> InstCombineContext<'tcx, 'a> { }) } - /// Remove assignments to inhabited ZST places. - fn combine_zst(&self, source_info: &SourceInfo, kind: &mut StatementKind<'tcx>) { - match kind { - StatementKind::Assign(box (place, _)) => { - let place_ty = place.ty(self.local_decls, self.tcx).ty; - if let Ok(layout) = self.tcx.layout_of(self.param_env.and(place_ty)) { - if layout.is_zst() && !layout.abi.is_uninhabited() { - if self.tcx.consider_optimizing(|| { - format!( - "InstCombine ZST - Place: {:?} SourceInfo: {:?}", - place, source_info - ) - }) { - *kind = StatementKind::Nop; - } - } - } - } - _ => {} - } - } - /// Transform boolean comparisons into logical operations. fn combine_bool_cmp(&self, source_info: &SourceInfo, rvalue: &mut Rvalue<'tcx>) { match rvalue { diff --git a/compiler/rustc_mir/src/transform/mod.rs b/compiler/rustc_mir/src/transform/mod.rs index 13546442f66..c9187fdeced 100644 --- a/compiler/rustc_mir/src/transform/mod.rs +++ b/compiler/rustc_mir/src/transform/mod.rs @@ -44,6 +44,7 @@ pub mod promote_consts; pub mod remove_noop_landing_pads; pub mod remove_storage_markers; pub mod remove_unneeded_drops; +pub mod remove_zsts; pub mod required_consts; pub mod rustc_peek; pub mod simplify; @@ -494,6 +495,7 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { // The main optimizations that we do on MIR. let optimizations: &[&dyn MirPass<'tcx>] = &[ &remove_storage_markers::RemoveStorageMarkers, + &remove_zsts::RemoveZsts, &const_goto::ConstGoto, &remove_unneeded_drops::RemoveUnneededDrops, &match_branches::MatchBranchSimplification, diff --git a/compiler/rustc_mir/src/transform/remove_zsts.rs b/compiler/rustc_mir/src/transform/remove_zsts.rs new file mode 100644 index 00000000000..838ffe9b596 --- /dev/null +++ b/compiler/rustc_mir/src/transform/remove_zsts.rs @@ -0,0 +1,49 @@ +//! Removes assignments to ZST places. + +use crate::transform::MirPass; +use rustc_data_structures::fx::FxHashMap; +use rustc_middle::mir::{Body, StatementKind}; +use rustc_middle::ty::TyCtxt; + +pub struct RemoveZsts; + +impl<'tcx> MirPass<'tcx> for RemoveZsts { + fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { + let param_env = tcx.param_env(body.source.def_id()); + + let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut(); + + let mut is_zst_cache = FxHashMap::default(); + + for block in basic_blocks.iter_mut() { + for statement in block.statements.iter_mut() { + match statement.kind { + StatementKind::Assign(box (place, _)) => { + let place_ty = place.ty(local_decls, tcx).ty; + + let is_inhabited_zst = *is_zst_cache.entry(place_ty).or_insert_with(|| { + if let Ok(layout) = tcx.layout_of(param_env.and(place_ty)) { + if layout.is_zst() && !layout.abi.is_uninhabited() { + return true; + } + } + false + }); + + if is_inhabited_zst { + if tcx.consider_optimizing(|| { + format!( + "RemoveZsts - Place: {:?} SourceInfo: {:?}", + place, statement.source_info + ) + }) { + statement.make_nop(); + } + } + } + _ => {} + } + } + } + } +} |