[Bug target/81763] Issues with BMI on 32bit x86 apps on GCC 7.1+

[manuel.lauss at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81763

--- Comment #27 from Manuel Lauss <manuel.lauss at googlemail dot com> ---
(In reply to Uroš Bizjak from comment #21)
> Following patch should fix the problem:
> 
> --cut here--
> Index: i386.md
> ===================================================================
> --- i386.md     (revision 256935)
> +++ i386.md     (working copy)
> @@ -9250,10 +9250,10 @@
>  })
>  
>  (define_insn "*andndi3_doubleword"
> -  [(set (match_operand:DI 0 "register_operand" "=r,&r")
> +  [(set (match_operand:DI 0 "register_operand" "=r,r")
>         (and:DI
>           (not:DI (match_operand:DI 1 "register_operand" "r,0"))
> -         (match_operand:DI 2 "nonimmediate_operand" "rm,rm")))
> +         (match_operand:DI 2 "nonimmediate_operand" "r,rm")))
>     (clobber (reg:CC FLAGS_REG))]
>    "!TARGET_64BIT && TARGET_STV && TARGET_SSE2"
>    "#"
> --cut here--
> 
> So, the pattern now reads:
> 
> (define_insn "*andndi3_doubleword"
>   [(set (match_operand:DI 0 "register_operand" "=r,r")
> 	(and:DI
> 	  (not:DI (match_operand:DI 1 "register_operand" "r,0"))
> 	  (match_operand:DI 2 "nonimmediate_operand" "r,rm")))
>    (clobber (reg:CC FLAGS_REG))]
>   "!TARGET_64BIT && TARGET_STV && TARGET_SSE2"
>   "#"
>   [(set_attr "isa" "bmi,*")])


I rebuilt gcc-7.3 with this applied, now the generated code looks much better:
  ab:   0f ad d0                shrd   %cl,%edx,%eax
  ae:   f6 c1 20                test   $0x20,%cl
  b1:   c4 e2 73 f7 d2          shrx   %ecx,%edx,%edx
  b6:   0f 45 c2                cmovne %edx,%eax
  b9:   0f 45 d5                cmovne %ebp,%edx
  bc:   c4 e2 68 f2 54 df 04    andn   0x4(%edi,%ebx,8),%edx,%edx
  c3:   89 d1                   mov    %edx,%ecx
  c5:   c4 e2 78 f2 04 df       andn   (%edi,%ebx,8),%eax,%eax
  cb:   09 c1                   or     %eax,%ecx

And it seems to work as well, 32bit llvm now built successfully.