This code is valid for any icmp, so we can safely look through a
freeze when trying to find one.
A caveat here is that replaceFoldableUses() may not end up replacing
any uses in this case. It might make sense to use the freeze as the
context instruction (rather than the terminator) if there is a
freeze, to ensure that it always gets folded. This would require
some changes to how replaceFoldedUses() works though, as it
currently assumes that the value is valid at the end of the block.
Compared to the optimized code with branch conditions never frozen,
limiting the type of freeze's operand causes generation of suboptimal code in
some cases.
I would like to suggest removing the constraint, as this patch does.
If the number of freeze instructions becomes significant, this can be revisited.
Differential Revision: https://reviews.llvm.org/D84949
This patch makes JumpThreading fold br(freeze(undef)) if the freeze instruction
is only used by the branch.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D84818
This patch adds a basic support for freeze instruction to JumpThreading
by making ComputeValueKnownInPredecessorsImpl look into its operand.
Reviewed By: efriedma, nikic
Differential Revision: https://reviews.llvm.org/D84598
