On Thu, Jan 7, 2021 at 9:56 AM Jakub Jelinek <ja...@redhat.com> wrote:
>
> Hi!
>
> The BLSI instruction sets SF and ZF based on the result and clears OF.
> CF is set to something unrelated.
>
> The following patch optimizes BLSI followed by comparison, so we don't need
> to emit a TEST insn in between.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2021-01-07 Jakub Jelinek <ja...@redhat.com>
>
> PR target/98567
> * config/i386/i386.md (*bmi_blsi_<mode>_cmp): New define_insn.
>
> * gcc.target/i386/pr98567-1.c: New test.
> * gcc.target/i386/pr98567-2.c: New test.
>
> --- gcc/config/i386/i386.md.jj 2021-01-04 10:25:45.072163178 +0100
> +++ gcc/config/i386/i386.md 2021-01-06 17:49:13.251966127 +0100
> @@ -14568,6 +14568,21 @@ (define_insn "*bmi_blsi_<mode>"
> (set_attr "btver2_decode" "double")
> (set_attr "mode" "<MODE>")])
>
> +(define_insn "*bmi_blsi_<mode>_cmp"
> + [(set (reg FLAGS_REG)
> + (compare
> + (and:SWI48
> + (neg:SWI48 (match_operand:SWI48 1 "nonimmediate_operand" "rm"))
> + (match_dup 1))
> + (const_int 0)))
> + (set (match_operand:SWI48 0 "register_operand" "=r")
> + (and:SWI48 (neg:SWI48 (match_dup 1)) (match_dup 1)))]
> + "TARGET_BMI && ix86_match_ccmode (insn, CCNOmode)"
> + "blsi\t{%1, %0|%0, %1}"
> + [(set_attr "type" "bitmanip")
> + (set_attr "btver2_decode" "double")
> + (set_attr "mode" "<MODE>")])
I wonder if we should also add _cc variant where scratch is used:
(define_insn "*bmi_blsi_<mode>_cc"
[(set (reg FLAGS_REG)
(compare
(and:SWI48
(neg:SWI48 (match_operand:SWI48 1 "nonimmediate_operand" "rm"))
(match_dup 1))
(const_int 0)))
(clobber (match_scratch:SWI48 0 "=r"))]
"TARGET_BMI && ix86_match_ccmode (insn, CCNOmode)"
"blsi\t{%1, %0|%0, %1}"
[(set_attr "type" "bitmanip")
(set_attr "btver2_decode" "double")
(set_attr "mode" "<MODE>")])
The output is unused in the testcases, so there may be no difference
in the generated code, but it looks to me that additional pattern
gives the compiler more freedom. Also note, that all other CC setting
insns come in three variants.
Otherwise OK.
Uros.
