[Ping ^ 4] [PATCH] Fix PR 61225

[Zhenqiang Chen <zhenqiang dot chen at linaro dot org>]

Ping?

Thanks!
-Zhenqiang

On 17 June 2014 12:53, Zhenqiang Chen <zhenqiang.chen@linaro.org> wrote:
> Ping?
>
> Thanks!
> -Zhenqiang
>
> On 9 June 2014 17:08, Zhenqiang Chen <zhenqiang.chen@linaro.org> wrote:
>> Ping ^2?
>>
>> Thanks!
>> -Zhenqiang
>>
>> On 28 May 2014 15:02, Zhenqiang Chen <zhenqiang.chen@linaro.org> wrote:
>>> Ping?
>>>
>>> Thanks!
>>> -Zhenqiang
>>>
>>> On 22 May 2014 17:52, Zhenqiang Chen <zhenqiang.chen@linaro.org> wrote:
>>>> On 21 May 2014 20:43, Steven Bosscher <stevenb.gcc@gmail.com> wrote:
>>>>> On Wed, May 21, 2014 at 11:58 AM, Zhenqiang Chen wrote:
>>>>>> Hi,
>>>>>>
>>>>>> The patch fixes the gcc.target/i386/pr49095.c FAIL in PR61225. The
>>>>>> test case tends to check a peephole2 optimization, which optimizes the
>>>>>> following sequence
>>>>>>
>>>>>>     2: bx:SI=ax:SI
>>>>>>     25: ax:SI=[bx:SI]
>>>>>>     7: {ax:SI=ax:SI-0x1;clobber flags:CC;}
>>>>>>     8: [bx:SI]=ax:SI
>>>>>>     9: flags:CCZ=cmp(ax:SI,0)
>>>>>> to
>>>>>>    2: bx:SI=ax:SI
>>>>>>    41: {flags:CCZ=cmp([bx:SI]-0x1,0);[bx:SI]=[bx:SI]-0x1;}
>>>>>>
>>>>>> The enhanced shrink-wrapping, which calls copyprop_hardreg_forward
>>>>>> changes the INSN 25 to
>>>>>>
>>>>>>     25: ax:SI=[ax:SI]
>>>>>>
>>>>>> Then peephole2 can not optimize it since two memory_operands look like
>>>>>> different.
>>>>>>
>>>>>> To fix it, the patch adds another peephole2 rule to read one more
>>>>>> insn. From the register copy, it knows the address is the same.
>>>>>
>>>>> That is one complex peephole2 to deal with a transformation like this.
>>>>> It seems to be like it's a too specific solution for a bigger problem.
>>>>>
>>>>> Could you please try one of the following solutions instead:
>>>>>
>>>>> 1. Track register values for peephole2 and try different alternatives
>>>>> based on known register equivalences? E.g. in your example, perhaps
>>>>> there is already a REG_EQUAL/REG_EQUIV note available on insn 25 after
>>>>> copyprop_hardreg_forward, to annotate that [ax:SI] is equivalent to
>>>>> [bx:SI] at that point (or if that information is not available, it is
>>>>> not very difficult to make it available). Then you could try applying
>>>>> peephole2 on the original pattern but also on patterns modified with
>>>>> the known equivalences (i.e. try peephole2 on multiple equivalent
>>>>> patterns for the same insn). This may expose other peephole2
>>>>> opportunities, not just the specific one your patch addresses.
>>>>
>>>> Patch is updated according to the comment. There is no REG_EQUAL. So I
>>>> add it when replace_oldest_value_reg.
>>>>
>>>> ChangeLog:
>>>> 2014-05-22  Zhenqiang Chen  <zhenqiang.chen@linaro.org>
>>>>
>>>>         Part of PR rtl-optimization/61225
>>>>         * config/i386/i386-protos.h (ix86_peephole2_rtx_equal_p): New proto.
>>>>         * config/i386/i386.c (ix86_peephole2_rtx_equal_p): New function.
>>>>         * regcprop.c (replace_oldest_value_reg): Add REG_EQUAL note when
>>>>         propagating to SET.
>>>>
>>>> diff --git a/gcc/config/i386/i386-protos.h b/gcc/config/i386/i386-protos.h
>>>> index 39462bd..0c4a2b9 100644
>>>> --- a/gcc/config/i386/i386-protos.h
>>>> +++ b/gcc/config/i386/i386-protos.h
>>>> @@ -42,6 +42,7 @@ extern enum calling_abi ix86_function_type_abi (const_tree);
>>>>
>>>>  extern void ix86_reset_previous_fndecl (void);
>>>>
>>>> +extern bool ix86_peephole2_rtx_equal_p (rtx, rtx, rtx, rtx);
>>>>  #ifdef RTX_CODE
>>>>  extern int standard_80387_constant_p (rtx);
>>>>  extern const char *standard_80387_constant_opcode (rtx);
>>>> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
>>>> index 6ffb788..583ebe8 100644
>>>> --- a/gcc/config/i386/i386.c
>>>> +++ b/gcc/config/i386/i386.c
>>>> @@ -46856,6 +46856,29 @@ ix86_atomic_assign_expand_fenv (tree *hold,
>>>> tree *clear, tree *update)
>>>>                     atomic_feraiseexcept_call);
>>>>  }
>>>>
>>>> +/* OP0 is the SET_DEST of INSN and OP1 is the SET_SRC of INSN.
>>>> +   Check whether OP1 and OP6 is equal.  */
>>>> +
>>>> +bool
>>>> +ix86_peephole2_rtx_equal_p (rtx insn, rtx op0, rtx op1, rtx op6)
>>>> +{
>>>> +  rtx note;
>>>> +
>>>> +  if (!reg_overlap_mentioned_p (op0, op1) && rtx_equal_p (op1, op6))
>>>> +    return true;
>>>> +
>>>> +  gcc_assert (single_set (insn)
>>>> +             && op0 == SET_DEST (single_set (insn))
>>>> +             && op1 == SET_SRC (single_set (insn)));
>>>> +
>>>> +  note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
>>>> +  if (note
>>>> +      && !reg_overlap_mentioned_p (op0, XEXP (note, 0))
>>>> +      && rtx_equal_p (XEXP (note, 0), op6))
>>>> +    return true;
>>>> +
>>>> +  return false;
>>>> +}
>>>>  /* Initialize the GCC target structure.  */
>>>>  #undef TARGET_RETURN_IN_MEMORY
>>>>  #define TARGET_RETURN_IN_MEMORY ix86_return_in_memory
>>>> diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
>>>> index 44e80ec..b57fc86 100644
>>>> --- a/gcc/config/i386/i386.md
>>>> +++ b/gcc/config/i386/i386.md
>>>> @@ -16996,11 +16996,12 @@
>>>>                      [(match_dup 0)
>>>>                       (match_operand:SWI 2 "<nonmemory_operand>")]))
>>>>               (clobber (reg:CC FLAGS_REG))])
>>>> -   (set (match_dup 1) (match_dup 0))
>>>> +   (set (match_operand:SWI 6 "memory_operand") (match_dup 0))
>>>>     (set (reg FLAGS_REG) (compare (match_dup 0) (const_int 0)))]
>>>>    "(TARGET_READ_MODIFY_WRITE || optimize_insn_for_size_p ())
>>>>     && peep2_reg_dead_p (4, operands[0])
>>>> -   && !reg_overlap_mentioned_p (operands[0], operands[1])
>>>> +   && ix86_peephole2_rtx_equal_p (peep2_next_insn (0), operands[0],
>>>> +                                 operands[1], operands[6])
>>>>     && !reg_overlap_mentioned_p (operands[0], operands[2])
>>>>     && (<MODE>mode != QImode
>>>>         || immediate_operand (operands[2], QImode)
>>>> diff --git a/gcc/regcprop.c b/gcc/regcprop.c
>>>> index 7a5a4f6..4e09724 100644
>>>> --- a/gcc/regcprop.c
>>>> +++ b/gcc/regcprop.c
>>>> @@ -510,6 +510,22 @@ replace_oldest_value_reg (rtx *loc, enum
>>>> reg_class cl, rtx insn,
>>>>         fprintf (dump_file, "insn %u: replaced reg %u with %u\n",
>>>>                  INSN_UID (insn), REGNO (*loc), REGNO (new_rtx));
>>>>
>>>> +      if (single_set (insn) && GET_CODE (PATTERN (insn)) == SET
>>>> +         && GET_MODE_CLASS (GET_MODE (SET_DEST (insn))) != MODE_CC
>>>> +         && GET_CODE (SET_SRC (single_set (insn))) != COMPARE)
>>>> +       {
>>>> +         rtx set = single_set (insn);
>>>> +         rtx dest = SET_DEST (set);
>>>> +
>>>> +         if (REG_P (dest) && REG_P (new_rtx)
>>>> +             && REGNO (dest) == REGNO (new_rtx))
>>>> +           /* REGNO of the NEW_RTX is modified by INSN.  No way to forwarded
>>>> +              it any more.  So add REG_EQUAL note to record its previous
>>>> +              value.  This note can be used to check whether two RTXs
>>>> +              equal or not.  */
>>>> +           add_reg_note (insn, REG_EQUAL, copy_rtx (SET_SRC (set)));
>>>> +       }
>>>> +
>>>>        validate_change (insn, loc, new_rtx, 1);
>>>>        return true;
>>>>      }