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Auto merge of #91279 - scottmcm:small-refactor, r=nagisa

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Small mir-opt refactor

Hopefully-non-controversial changes from some not-ready-yet work that I'd figured I'd submit on their own.
This commit is contained in:
bors 2021-12-06 13:04:18 +00:00
commit 0fb1c371d4
4 changed files with 11 additions and 23 deletions
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1
compiler/rustc_middle/src/mir/mod.rs
View File

@ -1519,6 +1519,7 @@ 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,

7
compiler/rustc_middle/src/mir/terminator.rs
View File

@ -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> {

15
compiler/rustc_mir_transform/src/const_goto.rs
View File

@ -83,20 +83,7 @@ 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,

11
compiler/rustc_mir_transform/src/simplify_branches.rs
View File

@ -33,15 +33,8 @@ impl<'tcx> MirPass<'tcx> for SimplifyConstCondition {
} => {
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;
}