[Bug target/32201] New: [4.3 Regression] Can not allocate %xmm0 register for variable blend insn

[Bug target/32201] New: [4.3 Regression] Can not allocate %xmm0 register for variable blend insn

[ubizjak at gmail dot com]

Currently, it is not possible to use SSE 4.1 variable blend instructions in asm
statements. These instructions require the third argument to be in %xmm0, but
gcc fails to allocate correct register even when (new) "z" constraint is used.

--cut here--
typedef float V4SFmode __attribute__((vector_size(16)));

V4SFmode t (V4SFmode a, V4SFmode b, V4SFmode c)
{
  V4SFmode ret;

  asm ("blenvdps %0, %2, %3" : "=x" (ret) : "0" (a), "x" (b), "z" (c));
  return ret;
}
--cut here--

gcc -O1 -msse

prxxx.c: In function 't':
prxxx.c:7: error: can't find a register in class 'SSE_FIRST_REG' while
reloading 'asm'
prxxx.c:7: error: 'asm' operand has impossible constraints


-- 
           Summary: [4.3 Regression] Can not allocate %xmm0 register for
                    variable blend insn
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: ssemmx, ra
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: ubizjak at gmail dot com
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
OtherBugsDependingO 32189
             nThis:


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32201

[Bug target/32201] Can not allocate %xmm0 register for variable blend insn

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2007-06-04 07:22 -------
How can this be a regression if the constraint is new?
Also it seems like you could use register asm("xmm0") to get the correct
register to be used.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.3 Regression] Can not    |Can not allocate %xmm0
                   |allocate %xmm0 register for |register for variable blend
                   |variable blend insn         |insn


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32201

[Bug target/32201] Can not allocate %xmm0 register for variable blend insn

[ubizjak at gmail dot com]

------- Comment #2 from ubizjak at gmail dot com  2007-06-04 07:39 -------
(In reply to comment #1)
> How can this be a regression if the constraint is new?

This is the same failure as PR32189, and that one is marked as a regression.

> Also it seems like you could use register asm("xmm0") to get the correct
> register to be used.

But please note that "c" argument is passed to the function via xmm2.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32201

[Bug target/32201] Can not allocate %xmm0 register for variable blend insn

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2007-06-04 07:50 -------
> > Also it seems like you could use register asm("xmm0") to get the correct
> > register to be used.
> But please note that "c" argument is passed to the function via xmm2.
So this is why GCC has register asm() extension is to get the correct register
to be used.  The code would look like:
typedef float V4SFmode __attribute__((vector_size(16)));

V4SFmode t (V4SFmode a, V4SFmode b, V4SFmode c)
{
 V4SFmode ret;
 register V4SFmode c1 asm("xmm0");
 c1 = c;

 asm ("blenvdps %0, %2, %3" : "=x" (ret) : "0" (a), "x" (b), "x" (c1));
 return ret;
}

Since c1 is already in xmm0, the register allocator knows it cannot use a as
xmm0 so there is still a move before the other move and after the asm.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32201

[Bug target/32201] Can not allocate %xmm0 register for variable blend insn

[pinskia at gcc dot gnu dot org]

------- Comment #4 from pinskia at gcc dot gnu dot org  2007-06-04 07:58 -------
Note local allocate should be able to figure the "z" constraint is only one
register and assign it to that pesdu-register.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32201

[Bug target/32201] Can not allocate %xmm0 register for variable blend insn

[ubizjak at gmail dot com]

------- Comment #5 from ubizjak at gmail dot com  2007-06-04 08:06 -------
Created an attachment (id=13655)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=13655&action=view)
Local alloc RTL dump

RTL dump of .c.163r.lreg


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32201

[Bug target/32201] Can not allocate %xmm0 register for variable blend insn

[ubizjak at gmail dot com]

------- Comment #6 from ubizjak at gmail dot com  2007-06-14 19:11 -------
Fixed in mainline.


-- 

ubizjak at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32201