On 1/26/2022 8:56 AM, Richard Biener via Gcc-patches wrote:
This adds the capability to value-numbering of treating complex
address expressions where the offset becomes invariant as equal
to a POINTER_PLUS_EXPR. This restores CSE that is now prevented
by early lowering of &MEM[ptr + CST] to a POINTER_PLUS_EXPR.
Unfortunately this regresses gcc.dg/asan/pr99673.c again.
Bootstrapped and tested on x86_64-unknown-linux-gnu - any
opinions?
Richard.
2022-01-26 Richard Biener <rguent...@suse.de>
PR tree-optimization/104162
* tree-ssa-sccvn.cc (vn_reference_lookup): Handle
&MEM[_1 + 5].a[i] like a POINTER_PLUS_EXPR if the offset
becomes invariant.
(vn_reference_insert): Likewise.
* gcc.dg/tree-ssa/ssa-fre-99.c: New testcase.
IIRC there's a handful of old regressions this might help. More than
once I've been tempted to do something similar in DOM -- with this
addition it's just one more reason we should be looking to drop DOM and
replace it with FRE going forward.
jeff
