https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85805
--- Comment #8 from Segher Boessenkool <segher at gcc dot gnu.org> --- Author: segher Date: Thu Jul 26 10:16:48 2018 New Revision: 262994 URL: https://gcc.gnu.org/viewcvs?rev=262994&root=gcc&view=rev Log: combine: Another hard register problem (PR85805) The current code in reg_nonzero_bits_for_combine allows using the reg_stat info when last_set_mode is a different integer mode. This is completely wrong for non-pseudos. For example, as in the PR, a value in a DImode hard register is set by eight writes to its constituent QImode parts. The value written to the DImode is not the same as that written to the lowest-numbered QImode! PR rtl-optimization/85805 * combine.c (reg_nonzero_bits_for_combine): Only use the last set value for hard registers if that was written in the same mode. Modified: trunk/gcc/ChangeLog trunk/gcc/combine.c
