diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/librustc_infer/infer/error_reporting/mod.rs | 2 | ||||
| -rw-r--r-- | src/librustc_mir/transform/match_branches.rs | 93 | ||||
| -rw-r--r-- | src/librustc_mir/transform/mod.rs | 2 |
3 files changed, 40 insertions, 57 deletions
diff --git a/src/librustc_infer/infer/error_reporting/mod.rs b/src/librustc_infer/infer/error_reporting/mod.rs index 26220698190..063246f79fe 100644 --- a/src/librustc_infer/infer/error_reporting/mod.rs +++ b/src/librustc_infer/infer/error_reporting/mod.rs @@ -827,7 +827,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { ty::GenericParamDefKind::Type { has_default, .. } => { Some((param.def_id, has_default)) } - ty::GenericParamDefKind::Const { .. } => None, // FIXME(const_generics:defaults) + ty::GenericParamDefKind::Const => None, // FIXME(const_generics:defaults) }) .peekable(); let has_default = { diff --git a/src/librustc_mir/transform/match_branches.rs b/src/librustc_mir/transform/match_branches.rs index 5dc84955add..5fab46f029f 100644 --- a/src/librustc_mir/transform/match_branches.rs +++ b/src/librustc_mir/transform/match_branches.rs @@ -1,4 +1,4 @@ -use crate::transform::{simplify, MirPass, MirSource}; +use crate::transform::{MirPass, MirSource}; use rustc_middle::mir::*; use rustc_middle::ty::TyCtxt; @@ -12,10 +12,9 @@ pub struct MatchBranchSimplification; impl<'tcx> MirPass<'tcx> for MatchBranchSimplification { fn run_pass(&self, tcx: TyCtxt<'tcx>, src: MirSource<'tcx>, body: &mut Body<'tcx>) { let param_env = tcx.param_env(src.def_id()); - let mut did_remove_blocks = false; let bbs = body.basic_blocks_mut(); 'outer: for bb_idx in bbs.indices() { - let (discr, val, switch_ty, targets) = match bbs[bb_idx].terminator().kind { + let (discr, val, switch_ty, first, second) = match bbs[bb_idx].terminator().kind { TerminatorKind::SwitchInt { discr: Operand::Move(ref place), switch_ty, @@ -23,60 +22,53 @@ impl<'tcx> MirPass<'tcx> for MatchBranchSimplification { ref values, .. } if targets.len() == 2 && values.len() == 1 => { - (place.clone(), values[0], switch_ty, targets) + (place, values[0], switch_ty, targets[0], targets[1]) } + // Only optimize switch int statements _ => continue, }; - let (first, rest) = if let ([first], rest) = targets.split_at(1) { - (*first, rest) - } else { - unreachable!(); - }; - let first_dest = bbs[first].terminator().kind.clone(); - let same_destinations = rest - .iter() - .map(|target| &bbs[*target].terminator().kind) - .all(|t_kind| t_kind == &first_dest); - if !same_destinations { + + // Check that destinations are identical, and if not, then don't optimize this block + if &bbs[first].terminator().kind != &bbs[second].terminator().kind { continue; } + + // Check that blocks are assignments of consts to the same place or same statement, + // and match up 1-1, if not don't optimize this block. let first_stmts = &bbs[first].statements; - for s in first_stmts.iter() { - match &s.kind { - StatementKind::Assign(box (_, rhs)) => { - if let Rvalue::Use(Operand::Constant(_)) = rhs { - } else { - continue 'outer; - } - } - _ => continue 'outer, - } + let scnd_stmts = &bbs[second].statements; + if first_stmts.len() != scnd_stmts.len() { + continue; } - for target in rest.iter() { - for s in bbs[*target].statements.iter() { - if let StatementKind::Assign(box (ref lhs, rhs)) = &s.kind { - if let Rvalue::Use(Operand::Constant(_)) = rhs { - let has_matching_assn = first_stmts - .iter() - .find(|s| { - if let StatementKind::Assign(box (lhs_f, _)) = &s.kind { - lhs_f == lhs - } else { - false - } - }) - .is_some(); - if has_matching_assn { - continue; + for (f, s) in first_stmts.iter().zip(scnd_stmts.iter()) { + match (&f.kind, &s.kind) { + // If two statements are exactly the same just ignore them. + (f_s, s_s) if f_s == s_s => (), + + ( + StatementKind::Assign(box (lhs_f, Rvalue::Use(Operand::Constant(f_c)))), + StatementKind::Assign(box (lhs_s, Rvalue::Use(Operand::Constant(s_c)))), + ) if lhs_f == lhs_s => { + if let Some(f_c) = f_c.literal.try_eval_bool(tcx, param_env) { + // This should also be a bool because it's writing to the same place + let s_c = s_c.literal.try_eval_bool(tcx, param_env).unwrap(); + // Check that only const assignments of opposite bool values are + // permitted. + if f_c != s_c { + continue } } + continue 'outer; } - - continue 'outer; + // If there are not exclusively assignments, then ignore this + _ => continue 'outer, } } - let (first_block, to_add) = bbs.pick2_mut(first, bb_idx); - let new_stmts = first_block.statements.iter().cloned().map(|mut s| { + // Take owenership of items now that we know we can optimize. + let discr = discr.clone(); + + bbs[bb_idx].terminator_mut().kind = TerminatorKind::Goto { target: first }; + for s in bbs[first].statements.iter_mut() { if let StatementKind::Assign(box (_, ref mut rhs)) = s.kind { let size = tcx.layout_of(param_env.and(switch_ty)).unwrap().size; let const_cmp = Operand::const_from_scalar( @@ -86,17 +78,8 @@ impl<'tcx> MirPass<'tcx> for MatchBranchSimplification { rustc_span::DUMMY_SP, ); *rhs = Rvalue::BinaryOp(BinOp::Eq, Operand::Move(discr), const_cmp); - } else { - unreachable!() } - s - }); - to_add.statements.extend(new_stmts); - to_add.terminator_mut().kind = first_dest; - did_remove_blocks = true; - } - if did_remove_blocks { - simplify::remove_dead_blocks(body); + } } } } diff --git a/src/librustc_mir/transform/mod.rs b/src/librustc_mir/transform/mod.rs index b84514d1e94..4f26f3bb459 100644 --- a/src/librustc_mir/transform/mod.rs +++ b/src/librustc_mir/transform/mod.rs @@ -441,6 +441,7 @@ fn run_optimization_passes<'tcx>( // with async primitives. &generator::StateTransform, &instcombine::InstCombine, + &match_branches::MatchBranchSimplification, &const_prop::ConstProp, &simplify_branches::SimplifyBranches::new("after-const-prop"), &simplify_try::SimplifyArmIdentity, @@ -452,7 +453,6 @@ fn run_optimization_passes<'tcx>( &simplify::SimplifyCfg::new("final"), &nrvo::RenameReturnPlace, &simplify::SimplifyLocals, - &match_branches::MatchBranchSimplification, ]; let no_optimizations: &[&dyn MirPass<'tcx>] = &[ |