https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122247
--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Andrew Pinski <[email protected]>: https://gcc.gnu.org/g:256fa1df0ed0e4ba955a1ea24b4b2b4a8325efa5 commit r16-4741-g256fa1df0ed0e4ba955a1ea24b4b2b4a8325efa5 Author: Andrew Pinski <[email protected]> Date: Tue Oct 28 20:29:45 2025 -0700 forwprop: Improve simple dse slightly more for eh but multiple incoming edges (phi) [PR122247] In this case we have a phi node for the use so we need to see if the result of the phi is a single usage with the clobber. That is the following IR: ``` # .MEM_6 = VDEF <.MEM_5(D)> inner = outer; # .MEM_7 = VDEF <.MEM_6> p (outer); <bb 3> : ... # .MEM_8 = VDEF <.MEM_7> g (_3, _2, _1); <bb 4> : # .MEM_9 = VDEF <.MEM_8> inner ={v} {CLOBBER(eos)}; ... <bb 5> : # .MEM_4 = PHI <.MEM_7(2), .MEM_8(3)> <L0>: # .MEM_10 = VDEF <.MEM_4> inner ={v} {CLOBBER(eos)}; ``` The two two clobber can be considered the same. So starting at `bb 4`'s. Bofore we walk back to the call of g statement and would notice that the use in the phi node of `bb5` and that would cause the walk to stop. But in this case since he phi node has a single use of the clobber and the clobber matches the original clobber it can be considered the same "one". So with the patch now, we walk back one more statement and allow it. Similar to the at the call to p statement. Bootstrapped and tested on x86_64-linux-gnu. PR tree-optimization/122247 gcc/ChangeLog: * tree-ssa-forwprop.cc (do_simple_agr_dse): Allow phi node for the usage if the usage of the phi result is just the "same" as the original clobber. gcc/testsuite/ChangeLog: * g++.dg/tree-ssa/copy-prop-aggregate-sra-2.C: New test. Signed-off-by: Andrew Pinski <[email protected]>
