bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

Auto merge of #106340 - saethlin:propagate-operands, r=oli-obk

Browse source 
Always permit ConstProp to exploit arithmetic identities

Fixes https://github.com/rust-lang/rust/issues/72751

Initially, I thought I would need to enable operand propagation then do something else, but actually https://github.com/rust-lang/rust/pull/74491 already has the fix for the issue in question! It looks like this optimization was put under MIR opt level 3 due to possible soundness/stability implications, then demoted further to MIR opt level 4 when MIR opt level 2 became associated with `--release`.

Perhaps in the past we were doing CTFE on optimized MIR? We aren't anymore, so this optimization has no stability implications.

r? `@oli-obk`
This commit is contained in:
bors 2023-01-09 11:59:51 +00:00
commit 89e0576bd3
4 changed files with 47 additions and 5 deletions
Download patch file Download diff file Expand all files Collapse all files

6
compiler/rustc_mir_transform/src/const_prop.rs
View file

@ -655,11 +655,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
return None;
}
if self.tcx.sess.mir_opt_level() >= 4 {
self.eval_rvalue_with_identities(rvalue, place)
} else {
self.use_ecx(|this| this.ecx.eval_rvalue_into_place(rvalue, place))
}
self.eval_rvalue_with_identities(rvalue, place)
}
// Attempt to use algebraic identities to eliminate constant expressions