On Fri, May 8, 2020 at 9:47 AM Jakub Jelinek <ja...@redhat.com> wrote:
>
> Hi!
>
> The following peephole2 changes:
> - addl (%rdi), %esi
> + xorl %eax, %eax
> + addl %esi, (%rdi)
> setc %al
> - movl %esi, (%rdi)
> - movzbl %al, %eax
> ret
> on the testcase. *add<mode>3_cc_overflow_1, being an add{l,q} insn, is
> commutative, so if TARGET_READ_MODIFY_WRITE we can replace
> addl (%rdi), %esi; movl %esi, (%rdi)
> with
> addl %esi, (%rdi)
> if %edi is dead after those two insns.
I assume you meant %esi here.
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2020-05-08 Jakub Jelinek <ja...@redhat.com>
>
> PR target/94857
> * config/i386/i386.md (peephole2 after *add<mode>3_cc_overflow_1): New
> define_peephole2.
>
> * gcc.target/i386/pr94857.c: New test.
OK with a small test adjustment.
Thanks,
Uros.
> --- gcc/config/i386/i386.md.jj 2020-05-06 20:03:38.489391717 +0200
> +++ gcc/config/i386/i386.md 2020-05-07 19:59:45.650521607 +0200
> @@ -6992,6 +6992,23 @@ (define_insn "*add<mode>3_cc_overflow_1"
> [(set_attr "type" "alu")
> (set_attr "mode" "<MODE>")])
>
> +(define_peephole2
> + [(parallel [(set (reg:CCC FLAGS_REG)
> + (compare:CCC
> + (plus:SWI (match_operand:SWI 0 "general_reg_operand")
> + (match_operand:SWI 1 "memory_operand"))
> + (match_dup 0)))
> + (set (match_dup 0) (plus:SWI (match_dup 0) (match_dup 1)))])
> + (set (match_dup 1) (match_dup 0))]
> + "(TARGET_READ_MODIFY_WRITE || optimize_insn_for_size_p ())
> + && peep2_reg_dead_p (2, operands[0])
> + && !reg_overlap_mentioned_p (operands[0], operands[1])"
> + [(parallel [(set (reg:CCC FLAGS_REG)
> + (compare:CCC
> + (plus:SWI (match_dup 1) (match_dup 0))
> + (match_dup 1)))
> + (set (match_dup 1) (plus:SWI (match_dup 1) (match_dup 0)))])])
> +
> (define_insn "*addsi3_zext_cc_overflow_1"
> [(set (reg:CCC FLAGS_REG)
> (compare:CCC
> --- gcc/testsuite/gcc.target/i386/pr94857.c.jj 2020-05-07 20:09:16.002907217
> +0200
> +++ gcc/testsuite/gcc.target/i386/pr94857.c 2020-05-07 20:08:46.533351730
> +0200
> @@ -0,0 +1,15 @@
> +/* PR target/94857 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -mtune=skylake -masm=att" } */
> +/* { dg-final { scan-assembler "\taddl\t%\[a-z0-9]\*, \\\(" } } */
> +
> +#ifndef __x86_64__
> +__attribute__((regparm(2)))
> +#endif
Better use:
/* { dg-additional-options "-mregparm=2" { target ia32 } } */
> +int
> +foo (unsigned *p, unsigned x)
> +{
> + unsigned u = *p;
> + *p += x;
> + return u > *p;
> +}
>
> Jakub
>
