ira.c update_equiv_regs patch causes gcc/testsuite/gcc.target/arm/pr43920-2.c regression

[Jeff Law]

On 04/17/2015 03:57 AM, Shiva Chen wrote:
> Hi,
>
> I think the rtl dump in
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64916
> is not jump2 phase rtl dump.
>
> Because jump2 is after ira, the register number should be hardware
> register number.
>
> the jump2 rtl dump should as follow
>
> ...
>     31: NOTE_INSN_BASIC_BLOCK 5
>     32: [r6:SI]=r4:SI
>        REG_DEAD r6:SI
>        REG_DEAD r4:SI
>     33: [r5:SI]=r0:SI
>        REG_DEAD r5:SI
>        REG_DEAD r0:SI
>      7: r0:SI=0
>        REG_EQUAL 0
>     85: use r0:SI
>     86: {return;sp:SI=sp:SI+0x18;r3:SI=[sp:SI];r4:SI=[sp:SI+0x4];r5:SI=[sp:SI+0x8];r6:SI=[sp:SI+0xc];r7:SI=[sp:SI+0x10];pc:SI=[sp:SI+0x14];}
>        REG_UNUSED pc:SI
>        REG_UNUSED r3:SI
>        REG_CFA_RESTORE r7:SI
>        REG_CFA_RESTORE r6:SI
>        REG_CFA_RESTORE r5:SI
>        REG_CFA_RESTORE r4:SI
>        REG_CFA_RESTORE r3:SI
>     77: barrier
>     46: L46:
>     45: NOTE_INSN_BASIC_BLOCK 6
>      8: r0:SI=r4:SI
>        REG_DEAD r4:SI
>        REG_EQUAL 0xffffffffffffffff
>     87: use r0:SI
>     88: {return;sp:SI=sp:SI+0x18;r3:SI=[sp:SI];r4:SI=[sp:SI+0x4];r5:SI=[sp:SI+0x8];r6:SI=[sp:SI+0xc];r7:SI=[sp:SI+0x10];pc:SI=[sp:SI+0x14];}
>        REG_UNUSED pc:SI
>        REG_UNUSED r3:SI
>        REG_CFA_RESTORE r7:SI
>        REG_CFA_RESTORE r6:SI
>        REG_CFA_RESTORE r5:SI
>        REG_CFA_RESTORE r4:SI
>        REG_CFA_RESTORE r3:SI
>     79: barrier
>     54: L54:
>     53: NOTE_INSN_BASIC_BLOCK 7
>      9: r0:SI=0xffffffffffffffff         <== lost REG_EQUAL after patch
>     34: L34:
>     35: NOTE_INSN_BASIC_BLOCK 8
>     41: use r0:SI
>     90: {return;sp:SI=sp:SI+0x18;r3:SI=[sp:SI];r4:SI=[sp:SI+0x4];r5:SI=[sp:SI+0x8];r6:SI=[sp:SI+0xc];r7:SI=[sp:SI+0x10];pc:SI=[sp:SI+0x14];}
>        REG_UNUSED pc:SI
>        REG_UNUSED r3:SI
>        REG_CFA_RESTORE r7:SI
>        REG_CFA_RESTORE r6:SI
>        REG_CFA_RESTORE r5:SI
>        REG_CFA_RESTORE r4:SI
>        REG_CFA_RESTORE r3:SI
>     89: barrier
Intead of the slim dump, can you please include the full RTL dump.  I 
find those much easier to read.



>
> Possible patch for  can_replace_by in cfgcleanup.c.
>
> -  if (!note1 || !note2 || !rtx_equal_p (XEXP (note1, 0), XEXP (note2, 0))
> -      || !CONST_INT_P (XEXP (note1, 0)))
> +
> +  if (!note1 || !CONST_INT_P (XEXP (note1, 0)))
>       return dir_none;
>
> +  if (note2)
> +    {
> +      if (!rtx_equal_p (XEXP (note1, 0), XEXP (note2, 0)))
> +       return dir_none;
> +    }
> +  else
> +    {
> +      if (!CONST_INT_P (SET_SRC (s2))
> +         || !rtx_equal_p (XEXP (note1, 0), SET_SRC (s2)))
> +       return dir_none;
> +    }
> +
>
> I'm not sure the idea is ok or it might crash something.
> Any suggestion would be very helpful.
Seems like you're on a reasonable path to me.  I suggest you stick with it.

Basically what it appears you're trying to do is unify insns from 
different blocks where one looks like

(set x y)  with an attached REG_EQUAL note

And the other looks like

(set x const_int)

Where the REG_EQUAL note has the same value as the const_int in the 
second set.

I think you'd want to handle both cases i1 has the note i2, no note and 
i1 has no note and i2 has a note.

Jeff

jeff