Fix x86 setcc + movzbl peephole2s (PR target/86314)

Hi!

These peephole2s assume that when matching insns like:
  [(parallel [(set (reg FLAGS_REG) (match_operand 0))
              (match_operand 4)])
that operands[4] must be a set of a register with operands[0]
as SET_SRC, but that isn't the case e.g. for:
(insn 9 8 10 2 (parallel [
            (set (reg:CCC 17 flags)
                (compare:CCC (unspec_volatile:DI [
                            (mem/v:DI (reg/v/f:DI 5 di [orig:94 p ] [94]) [-1  S8 A64])
                            (const_int 5 [0x5])
                        ] UNSPECV_XCHG)
                    (const_int 0 [0])))
            (set (zero_extract:DI (mem/v:DI (reg/v/f:DI 5 di [orig:94 p ] [94]) [-1  S8 A64])
                    (const_int 1 [0x1])
                    (reg:DI 0 ax [96]))
                (const_int 1 [0x1]))
        ]) "pr86314.C":7 5268 {atomic_bit_test_and_setdi_1}
     (expr_list:REG_DEAD (reg/v/f:DI 5 di [orig:94 p ] [94])
        (expr_list:REG_DEAD (reg:DI 0 ax [96])
            (nil))))

As we want to clear operands[3] before this instruction, we need to
verify that it isn't used in operands[0] (we check that) and that
operands[4] does not set it (also checked), but also need to check that
operands[4] doesn't use it (which we don't do).  In the usual case
when SET_DEST of operands[4] is a REG and SET_SRC is operands[0] it
makes no difference, but if SET_DEST sets something that uses operands[3]
in it, or if SET_SRC is different from operands[0] and uses operands[3],
then this results in a wrong peephole2 transformation.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk and release branches?

2018-06-26  Jakub Jelinek  <jakub@redhat.com>

	PR target/86314
	* config/i386/i386.md (setcc + movzbl to xor + setcc peephole2s):
	Check reg_overlap_mentioned_p in addition to reg_set_p with the same
	operands.

	* gcc.dg/pr86314.c: New test.


	Jakub

On Tue, Jun 26, 2018 at 12:52 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> These peephole2s assume that when matching insns like:
>   [(parallel [(set (reg FLAGS_REG) (match_operand 0))
>               (match_operand 4)])
> that operands[4] must be a set of a register with operands[0]
> as SET_SRC, but that isn't the case e.g. for:
> (insn 9 8 10 2 (parallel [
>             (set (reg:CCC 17 flags)
>                 (compare:CCC (unspec_volatile:DI [
>                             (mem/v:DI (reg/v/f:DI 5 di [orig:94 p ] [94]) [-1  S8 A64])
>                             (const_int 5 [0x5])
>                         ] UNSPECV_XCHG)
>                     (const_int 0 [0])))
>             (set (zero_extract:DI (mem/v:DI (reg/v/f:DI 5 di [orig:94 p ] [94]) [-1  S8 A64])
>                     (const_int 1 [0x1])
>                     (reg:DI 0 ax [96]))
>                 (const_int 1 [0x1]))
>         ]) "pr86314.C":7 5268 {atomic_bit_test_and_setdi_1}
>      (expr_list:REG_DEAD (reg/v/f:DI 5 di [orig:94 p ] [94])
>         (expr_list:REG_DEAD (reg:DI 0 ax [96])
>             (nil))))
>
> As we want to clear operands[3] before this instruction, we need to
> verify that it isn't used in operands[0] (we check that) and that
> operands[4] does not set it (also checked), but also need to check that
> operands[4] doesn't use it (which we don't do).  In the usual case
> when SET_DEST of operands[4] is a REG and SET_SRC is operands[0] it
> makes no difference, but if SET_DEST sets something that uses operands[3]
> in it, or if SET_SRC is different from operands[0] and uses operands[3],
> then this results in a wrong peephole2 transformation.
>
> Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> trunk and release branches?
>
> 2018-06-26  Jakub Jelinek  <jakub@redhat.com>
>
>         PR target/86314
>         * config/i386/i386.md (setcc + movzbl to xor + setcc peephole2s):
>         Check reg_overlap_mentioned_p in addition to reg_set_p with the same
>         operands.
>
>         * gcc.dg/pr86314.c: New test.

OK everywhere.

Thanks,
Uros.

> --- gcc/config/i386/i386.md.jj  2018-06-25 14:51:24.878990827 +0200
> +++ gcc/config/i386/i386.md     2018-06-26 10:01:43.042907384 +0200
> @@ -12761,6 +12761,7 @@ (define_peephole2
>    "(peep2_reg_dead_p (3, operands[1])
>      || operands_match_p (operands[1], operands[3]))
>     && ! reg_overlap_mentioned_p (operands[3], operands[0])
> +   && ! reg_overlap_mentioned_p (operands[3], operands[4])
>     && ! reg_set_p (operands[3], operands[4])
>     && peep2_regno_dead_p (0, FLAGS_REG)"
>    [(parallel [(set (match_dup 5) (match_dup 0))
> @@ -12786,6 +12787,7 @@ (define_peephole2
>      || operands_match_p (operands[2], operands[4]))
>     && ! reg_overlap_mentioned_p (operands[4], operands[0])
>     && ! reg_overlap_mentioned_p (operands[4], operands[1])
> +   && ! reg_overlap_mentioned_p (operands[4], operands[5])
>     && ! reg_set_p (operands[4], operands[5])
>     && refers_to_regno_p (FLAGS_REG, operands[1], (rtx *)NULL)
>     && peep2_regno_dead_p (0, FLAGS_REG)"
> @@ -12835,6 +12837,7 @@ (define_peephole2
>    "(peep2_reg_dead_p (3, operands[1])
>      || operands_match_p (operands[1], operands[3]))
>     && ! reg_overlap_mentioned_p (operands[3], operands[0])
> +   && ! reg_overlap_mentioned_p (operands[3], operands[4])
>     && ! reg_set_p (operands[3], operands[4])
>     && peep2_regno_dead_p (0, FLAGS_REG)"
>    [(parallel [(set (match_dup 5) (match_dup 0))
> @@ -12861,6 +12864,7 @@ (define_peephole2
>      || operands_match_p (operands[2], operands[4]))
>     && ! reg_overlap_mentioned_p (operands[4], operands[0])
>     && ! reg_overlap_mentioned_p (operands[4], operands[1])
> +   && ! reg_overlap_mentioned_p (operands[4], operands[5])
>     && ! reg_set_p (operands[4], operands[5])
>     && refers_to_regno_p (FLAGS_REG, operands[1], (rtx *)NULL)
>     && peep2_regno_dead_p (0, FLAGS_REG)"
> --- gcc/testsuite/gcc.dg/pr86314.c.jj   2018-06-26 10:25:35.190160477 +0200
> +++ gcc/testsuite/gcc.dg/pr86314.c      2018-06-26 10:24:42.310077331 +0200
> @@ -0,0 +1,20 @@
> +// PR target/86314
> +// { dg-do run { target sync_int_long } }
> +// { dg-options "-O2" }
> +
> +__attribute__((noinline, noclone)) unsigned long
> +foo (unsigned long *p)
> +{
> +  unsigned long m = 1UL << ((*p & 1) ? 1 : 0);
> +  unsigned long n = __atomic_fetch_or (p, m, __ATOMIC_SEQ_CST);
> +  return (n & m) == 0;
> +}
> +
> +int
> +main ()
> +{
> +  unsigned long v = 1;
> +  if (foo (&v) != 1)
> +    __builtin_abort ();
> +  return 0;
> +}
>
>         Jakub