Re: PATCH [10/n]: Prepare x32: PR rtl-optimization/49114: Reload failed to handle (set reg:X (plus:X (subreg:X (reg:Y) 0) (const

["H.J. Lu" <hjl.tools@gmail.com>]

On Mon, Jun 27, 2011 at 3:25 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Mon, Jun 27, 2011 at 3:19 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Mon, Jun 27, 2011 at 3:08 PM, Ulrich Weigand <uweigand@de.ibm.com> wrote:
>>> H.J. Lu wrote:
>>>
>>>> reload generates:
>>>>
>>>> (insn 914 912 0 (set (reg:SI 0 ax)
>>>>         (plus:SI (subreg:SI (reg/v/f:DI 182 [ b ]) 0)
>>>>             (const_int 8 [0x8]))) 248 {*lea_1_x32}
>>>>      (nil))
>>>>
>>>> from
>>>>
>>>> insn = emit_insn_if_valid_for_reload (gen_rtx_SET (VOIDmode, out, in));
>>>
>>> Interesting.  The pseudo should have been replaced by the
>>> hard register (reg:DI 1) during the preceding call to
>>>      op0 = find_replacement (&XEXP (in, 0));
>>> (since reload 0 should have pushed a replacement record.)
>>>
>>> Interestingly enough, in the final output that replacement *is*
>>> performed in the REG_EQUIV note:
>>>
>>> (insn 1023 1022 1024 34 (set (reg:SI 1 dx)
>>>        (plus:SI (reg:SI 1 dx)
>>>            (const_int 8 [0x8]))) spooles.c:291 248 {*lea_1_x32}
>>>     (expr_list:REG_EQUIV (plus:SI (subreg:SI (reg:DI 1 dx) 0)
>>>            (const_int 8 [0x8]))
>>>        (nil)))
>>>
>>> which is why I hadn't expected this to be a problem here.
>>>
>>> Can you try to find out why the find_replacement doesn't work
>>> with your test case?
>>>
>>
>> I will investigate.  Could (reg:SI 1 dx) vs  (subreg:SI (reg:DI 1 dx) 0)
>> a problem?
>>
>
> find_replacement never checks subreg:
>
> Breakpoint 3, find_replacement (loc=0x7ffff068ab00)
>    at /export/gnu/import/git/gcc-x32/gcc/reload.c:6411
> 6411          if (reloadreg && r->where == loc)
> (reg:DI 0 ax)
> (reg/v/f:DI 182 [ b ])
> (gdb) call debug_rtx (*loc)
> (subreg:SI (reg/v/f:DI 182 [ b ]) 0)
> (gdb)
>

This seems to work.  Does it make any senses?

Thanks.


-- 
H.J.
---
diff --git a/gcc/reload.c b/gcc/reload.c
index 3ad46b9..bdc47d3 100644
--- a/gcc/reload.c
+++ b/gcc/reload.c
@@ -6415,6 +6415,26 @@ find_replacement (rtx *loc)

 	  return reloadreg;
 	}
+      else if (reloadreg
+	       && REG_P (reloadreg)
+	       && !r->subreg_loc
+	       && GET_CODE (*loc) == SUBREG
+	       && r->where == &SUBREG_REG (*loc))
+	{
+	  int offset;
+
+	  if (r->mode != VOIDmode && GET_MODE (reloadreg) != r->mode)
+	    reloadreg = gen_rtx_REG (r->mode, REGNO (reloadreg));
+
+	  offset = (GET_MODE_SIZE (GET_MODE (reloadreg))
+		    - GET_MODE_SIZE (GET_MODE (*loc)));
+
+	  if (! BYTES_BIG_ENDIAN)
+	    offset = (offset / UNITS_PER_WORD) * UNITS_PER_WORD;
+	  else if (! WORDS_BIG_ENDIAN)
+	    offset %= UNITS_PER_WORD;
+	  return gen_rtx_SUBREG (GET_MODE (*loc), reloadreg, offset);
+	}
       else if (reloadreg && r->subreg_loc == loc)
 	{
 	  /* RELOADREG must be either a REG or a SUBREG.