[Bug rtl-optimization/54792] [4.8 Regression] -fcompare-debug failures introduced by r191493

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54792

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-10-03 09:59:05 UTC ---
Created attachment 28340
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28340
gcc48-pr54792.patch

Untested fix.  The problem appears to be that find_modifiable_mems wasn't
scanning the TAIL insn, without -g on the testcase there was a load from memory
at the end of a basic block and it wasn't scanned, with -g there were some
DEBUG_INSNs after it, thus tail was a DEBUG_INSN and the load was scanned and
triggered the optimization.