From 9b0fc6202bf295e2518f7a781ca069c71c81698f Mon Sep 17 00:00:00 2001 From: Simon Vandel Sillesen Date: Thu, 3 Sep 2020 19:48:27 +0200 Subject: [PATCH] Generalize to Eq(true, _place) and Eq(_place, true) --- .../rustc_mir/src/transform/instcombine.rs | 45 ++++++++++++------- .../mir-opt/equal_true.opt.InstCombine.diff | 35 +++++++++++++++ src/test/mir-opt/equal_true.rs | 9 ++++ 3 files changed, 74 insertions(+), 15 deletions(-) create mode 100644 src/test/mir-opt/equal_true.opt.InstCombine.diff create mode 100644 src/test/mir-opt/equal_true.rs diff --git a/compiler/rustc_mir/src/transform/instcombine.rs b/compiler/rustc_mir/src/transform/instcombine.rs index 18cf2a2ff21..c4924cf16ab 100644 --- a/compiler/rustc_mir/src/transform/instcombine.rs +++ b/compiler/rustc_mir/src/transform/instcombine.rs @@ -66,7 +66,7 @@ impl<'tcx> MutVisitor<'tcx> for InstCombineVisitor<'tcx> { *rvalue = Rvalue::Use(Operand::Constant(box constant)); } - if let Some(operand) = self.optimizations.unneeded_not_equal.remove(&location) { + if let Some(operand) = self.optimizations.unneeded_equality_comparison.remove(&location) { debug!("replacing {:?} with {:?}", rvalue, operand); *rvalue = Rvalue::Use(operand); } @@ -87,14 +87,39 @@ impl OptimizationFinder<'b, 'tcx> { OptimizationFinder { body, tcx, optimizations: OptimizationList::default() } } - fn find_operand_in_ne_false_pattern( + fn find_unneeded_equality_comparison(&mut self, rvalue: &Rvalue<'tcx>, location: Location) { + // find Ne(_place, false) or Ne(false, _place) + // or Eq(_place, true) or Eq(true, _place) + if let Rvalue::BinaryOp(op, l, r) = rvalue { + let const_to_find = if *op == BinOp::Ne { + false + } else if *op == BinOp::Eq { + true + } else { + return; + }; + // (const, _place) + if let Some(o) = self.find_operand_in_equality_comparison_pattern(l, r, const_to_find) { + self.optimizations.unneeded_equality_comparison.insert(location, o.clone()); + } + // (_place, const) + else if let Some(o) = + self.find_operand_in_equality_comparison_pattern(r, l, const_to_find) + { + self.optimizations.unneeded_equality_comparison.insert(location, o.clone()); + } + } + } + + fn find_operand_in_equality_comparison_pattern( &self, l: &Operand<'tcx>, r: &'a Operand<'tcx>, + const_to_find: bool, ) -> Option<&'a Operand<'tcx>> { let const_ = l.constant()?; if const_.literal.ty == self.tcx.types.bool - && const_.literal.val.try_to_bool() == Some(false) + && const_.literal.val.try_to_bool() == Some(const_to_find) { if r.place().is_some() { return Some(r); @@ -128,17 +153,7 @@ impl Visitor<'tcx> for OptimizationFinder<'b, 'tcx> { } } - // find Ne(_place, false) or Ne(false, _place) - if let Rvalue::BinaryOp(BinOp::Ne, l, r) = rvalue { - // (false, _place) - if let Some(o) = self.find_operand_in_ne_false_pattern(l, r) { - self.optimizations.unneeded_not_equal.insert(location, o.clone()); - } - // (_place, false) - else if let Some(o) = self.find_operand_in_ne_false_pattern(r, l) { - self.optimizations.unneeded_not_equal.insert(location, o.clone()); - } - } + self.find_unneeded_equality_comparison(rvalue, location); self.super_rvalue(rvalue, location) } @@ -148,5 +163,5 @@ impl Visitor<'tcx> for OptimizationFinder<'b, 'tcx> { struct OptimizationList<'tcx> { and_stars: FxHashSet, arrays_lengths: FxHashMap>, - unneeded_not_equal: FxHashMap>, + unneeded_equality_comparison: FxHashMap>, } diff --git a/src/test/mir-opt/equal_true.opt.InstCombine.diff b/src/test/mir-opt/equal_true.opt.InstCombine.diff new file mode 100644 index 00000000000..a26776e70d6 --- /dev/null +++ b/src/test/mir-opt/equal_true.opt.InstCombine.diff @@ -0,0 +1,35 @@ +- // MIR for `opt` before InstCombine ++ // MIR for `opt` after InstCombine + + fn opt(_1: bool) -> i32 { + debug x => _1; // in scope 0 at $DIR/equal_true.rs:3:8: 3:9 + let mut _0: i32; // return place in scope 0 at $DIR/equal_true.rs:3:20: 3:23 + let mut _2: bool; // in scope 0 at $DIR/equal_true.rs:4:8: 4:17 + let mut _3: bool; // in scope 0 at $DIR/equal_true.rs:4:8: 4:9 + + bb0: { + StorageLive(_2); // scope 0 at $DIR/equal_true.rs:4:8: 4:17 + StorageLive(_3); // scope 0 at $DIR/equal_true.rs:4:8: 4:9 + _3 = _1; // scope 0 at $DIR/equal_true.rs:4:8: 4:9 +- _2 = Eq(move _3, const true); // scope 0 at $DIR/equal_true.rs:4:8: 4:17 ++ _2 = move _3; // scope 0 at $DIR/equal_true.rs:4:8: 4:17 + StorageDead(_3); // scope 0 at $DIR/equal_true.rs:4:16: 4:17 + switchInt(_2) -> [false: bb1, otherwise: bb2]; // scope 0 at $DIR/equal_true.rs:4:5: 4:34 + } + + bb1: { + _0 = const 1_i32; // scope 0 at $DIR/equal_true.rs:4:31: 4:32 + goto -> bb3; // scope 0 at $DIR/equal_true.rs:4:5: 4:34 + } + + bb2: { + _0 = const 0_i32; // scope 0 at $DIR/equal_true.rs:4:20: 4:21 + goto -> bb3; // scope 0 at $DIR/equal_true.rs:4:5: 4:34 + } + + bb3: { + StorageDead(_2); // scope 0 at $DIR/equal_true.rs:5:1: 5:2 + return; // scope 0 at $DIR/equal_true.rs:5:2: 5:2 + } + } + diff --git a/src/test/mir-opt/equal_true.rs b/src/test/mir-opt/equal_true.rs new file mode 100644 index 00000000000..994cd194a45 --- /dev/null +++ b/src/test/mir-opt/equal_true.rs @@ -0,0 +1,9 @@ +// EMIT_MIR equal_true.opt.InstCombine.diff + +fn opt(x: bool) -> i32 { + if x == true { 0 } else { 1 } +} + +fn main() { + opt(true); +}