https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107407
--- Comment #6 from CVS Commits ---
The releases/gcc-12 branch has been updated by Richard Biener
:
https://gcc.gnu.org/g:e0e37f97e67c99604129eeac2e73ccd3719ccb28
commit r12-8973-ge0e37f97e67c99604129eeac2e73ccd3719ccb28
Author: Richard Biener
Date: Fri Oct 28 15:03:49 2022 +0200
tree-optimization/107407 - wrong code with DSE
So what happens is that we elide processing of this check with
/* In addition to kills we can remove defs whose only use
is another def in defs. That can only ever be PHIs of which
we track two for simplicity reasons, the first and last in
{first,last}_phi_def (we fail for multiple PHIs anyways).
We can also ignore defs that feed only into
already visited PHIs. */
else if (single_imm_use (vdef, _p, _stmt)
&& (use_stmt == first_phi_def
|| use_stmt == last_phi_def
|| (gimple_code (use_stmt) == GIMPLE_PHI
&& bitmap_bit_p (visited,
SSA_NAME_VERSION
(PHI_RESULT (use_stmt))
where we have the last PHI being the outer loop virtual PHI and the first
PHI being the loop exit PHI of the outer loop and we've already processed
the single immediate use of the outer loop PHI, the inner loop PHI. But
we still have to perform the above check!
It's easiest to perform the check when we visit the PHI node instead of
delaying it to the actual processing loop.
PR tree-optimization/107407
* tree-ssa-dse.cc (dse_classify_store): Perform backedge
varying index check when collecting PHI uses rather than
after optimizing processing of the candidate defs.
* gcc.dg/torture/pr107407.c: New testcase.
(cherry picked from commit 031a400e49d8db156c43f9ec0b21ab0c2aee8c6d)
