https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110206
--- Comment #14 from Uroš Bizjak <ubizjak at gmail dot com> --- (In reply to Uroš Bizjak from comment #10) > (In reply to Uroš Bizjak from comment #9) > > and simplify_replace_rtx simplifies the above to: > > > > (gdb) p debug_rtx (src) > > (const_vector:V8HI [ > > (const_int 204 [0xcc]) repeated x8 > > ]) > > Patched compiler simplifies to: > > (gdb) p debug_rtx (src) > (const_vector:V8HI [ > (const_int 204 [0xcc]) repeated x4 > (const_int 0 [0]) repeated x4 > ]) The patched compiler puts the above in REG_EQUAL note. While the value is "more correct", I don't think the compiler has the right to set REG_EQUAL note when the top 4 bytes are actually undefined (as a result of an operation with an undefined input, which is the case with paradoxical subreg).
