https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82261
--- Comment #3 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Michael Clark from comment #2)
> Just refreshing this issue. I found it while testing some code-gen on
> Godbolt:
The combiner creates:
Failed to match this instruction:
(parallel [
(set (reg:SI 89)
(ior:SI (ashift:SI (reg:SI 94)
(subreg:QI (reg/v:SI 88 [ n ]) 0))
(lshiftrt:SI (reg:SI 95)
(minus:QI (subreg:QI (reg:SI 91) 0)
(subreg:QI (reg/v:SI 88 [ n ]) 0)))))
(clobber (reg:CC 17 flags))
])
This is *almost* matched by:
(define_insn "x86_shld"
[(set (match_operand:SI 0 "nonimmediate_operand" "+r*m")
(ior:SI (ashift:SI (match_dup 0)
(match_operand:QI 2 "nonmemory_operand" "Ic"))
(lshiftrt:SI (match_operand:SI 1 "register_operand" "r")
(minus:QI (const_int 32) (match_dup 2)))))
(clobber (reg:CC FLAGS_REG))]
but RTL combiner doesn't propagate (const_int 32) into the pattern.
I wonder if tree combiner can help here.
