diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs index 253ac266bed..d113dc696a1 100644 --- a/compiler/rustc_middle/src/mir/mod.rs +++ b/compiler/rustc_middle/src/mir/mod.rs @@ -1504,6 +1504,7 @@ impl Statement<'_> { } /// Changes a statement to a nop and returns the original statement. + #[must_use = "If you don't need the statement, use `make_nop` instead"] pub fn replace_nop(&mut self) -> Self { Statement { source_info: self.source_info, diff --git a/compiler/rustc_middle/src/mir/terminator.rs b/compiler/rustc_middle/src/mir/terminator.rs index e78b6fd092d..e33fb1acb6e 100644 --- a/compiler/rustc_middle/src/mir/terminator.rs +++ b/compiler/rustc_middle/src/mir/terminator.rs @@ -78,6 +78,13 @@ impl SwitchTargets { pub fn all_targets_mut(&mut self) -> &mut [BasicBlock] { &mut self.targets } + + /// Finds the `BasicBlock` to which this `SwitchInt` will branch given the + /// specific value. This cannot fail, as it'll return the `otherwise` + /// branch if there's not a specific match for the value. + pub fn target_for_value(&self, value: u128) -> BasicBlock { + self.iter().find_map(|(v, t)| (v == value).then_some(t)).unwrap_or_else(|| self.otherwise()) + } } pub struct SwitchTargetsIter<'a> { diff --git a/compiler/rustc_mir_transform/src/const_goto.rs b/compiler/rustc_mir_transform/src/const_goto.rs index d319fdcaa6b..c96e6f9d80b 100644 --- a/compiler/rustc_mir_transform/src/const_goto.rs +++ b/compiler/rustc_mir_transform/src/const_goto.rs @@ -82,20 +82,7 @@ impl<'a, 'tcx> Visitor<'tcx> for ConstGotoOptimizationFinder<'a, 'tcx> { // Now find which value in the Switch matches the const value. let const_value = _const.literal.try_eval_bits(self.tcx, self.param_env, switch_ty)?; - let found_value_idx_option = targets - .iter() - .enumerate() - .find(|(_, (value, _))| const_value == *value) - .map(|(idx, _)| idx); - - let target_to_use_in_goto = - if let Some(found_value_idx) = found_value_idx_option { - targets.iter().nth(found_value_idx).unwrap().1 - } else { - // If we did not find the const value in values, it must be the otherwise case - targets.otherwise() - }; - + let target_to_use_in_goto = targets.target_for_value(const_value); self.optimizations.push(OptimizationToApply { bb_with_goto: location.block, target_to_use_in_goto, diff --git a/compiler/rustc_mir_transform/src/simplify_branches.rs b/compiler/rustc_mir_transform/src/simplify_branches.rs index df90cfa318d..d8fc4aa9a6a 100644 --- a/compiler/rustc_mir_transform/src/simplify_branches.rs +++ b/compiler/rustc_mir_transform/src/simplify_branches.rs @@ -34,15 +34,8 @@ impl<'tcx> MirPass<'tcx> for SimplifyBranches { } => { let constant = c.literal.try_eval_bits(tcx, param_env, switch_ty); if let Some(constant) = constant { - let otherwise = targets.otherwise(); - let mut ret = TerminatorKind::Goto { target: otherwise }; - for (v, t) in targets.iter() { - if v == constant { - ret = TerminatorKind::Goto { target: t }; - break; - } - } - ret + let target = targets.target_for_value(constant); + TerminatorKind::Goto { target } } else { continue; }