bjoernager/rust
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[mir-opt] Disable the ConsideredEqual logic in SimplifyBranchSame opt

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The logic is currently broken and we need to disable it to fix a beta
regression (see #76803)
This commit is contained in:
Wesley Wiser 2020-09-17 09:29:39 -04:00
parent 95386b656e
commit dbd7226d29
3 changed files with 41 additions and 18 deletions
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11
compiler/rustc_mir/src/transform/simplify_try.rs
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@ -612,7 +612,7 @@ impl<'a, 'tcx> SimplifyBranchSameOptimizationFinder<'a, 'tcx> {
&& bb_l.terminator().kind == bb_r.terminator().kind;
let statement_check = || {
bb_l.statements.iter().zip(&bb_r.statements).try_fold(StatementEquality::TrivialEqual, |acc,(l,r)| {
let stmt_equality = self.statement_equality(*adt_matched_on, &l, bb_l_idx, &r, bb_r_idx);
let stmt_equality = self.statement_equality(*adt_matched_on, &l, bb_l_idx, &r, bb_r_idx, self.tcx.sess.opts.debugging_opts.mir_opt_level);
if matches!(stmt_equality, StatementEquality::NotEqual) {
// short circuit
None
@ -672,6 +672,7 @@ impl<'a, 'tcx> SimplifyBranchSameOptimizationFinder<'a, 'tcx> {
x_bb_idx: BasicBlock,
y: &Statement<'tcx>,
y_bb_idx: BasicBlock,
mir_opt_level: usize,
) -> StatementEquality {
let helper = |rhs: &Rvalue<'tcx>,
place: &Place<'tcx>,
@ -690,7 +691,13 @@ impl<'a, 'tcx> SimplifyBranchSameOptimizationFinder<'a, 'tcx> {
match rhs {
Rvalue::Use(operand) if operand.place() == Some(adt_matched_on) => {
StatementEquality::ConsideredEqual(side_to_choose)
// FIXME(76803): This logic is currently broken because it does not take into
// account the current discriminant value.
if mir_opt_level > 2 {
StatementEquality::ConsideredEqual(side_to_choose)
} else {
StatementEquality::NotEqual
}
}
_ => {
trace!(