[Bug target/43118] New: vld4 and vst4 intrinsics are not handled correctly

[Bug target/43118] New: vld4 and vst4 intrinsics are not handled correctly

[samuel dot rodal at nokia dot com]

The vldX and vstX variation of NEON intrinsics, where X > 1, seem to cause the
compiler to generate an obscene amount of code.

Example:

void blend1(uint8_t *src, uint8_t *dst)
{
        uint8x8_t temp = vld1_u8(src);
        vst1_u8(dst, temp);
}

generates the sensible

        vld1.8  {d16}, [r0]
        vst1.8  {d16}, [r1]
        bx      lr

Whereas:

void blend4(uint8_t *src, uint8_t *dst)
{
        uint8x8x4_t temp = vld4_u8(src);
        vst4_u8(dst, temp);
}

generates

        stmfd   sp!, {r4, r5, r6}
        .save {r4, r5, r6}
.LCFI4:
        .pad #132
        sub     sp, sp, #132
.LCFI5:
        vld4.8  {d16-d19}, [r0]
        add     r6, sp, #64
        vstmia  r6, {d16-d19}
        mov     r5, r1
        ldmia   r6!, {r0, r1, r2, r3}
        add     ip, sp, #96
        mov     r4, ip
        stmia   r4!, {r0, r1, r2, r3}
        ldmia   r6, {r0, r1, r2, r3}
        stmia   r4, {r0, r1, r2, r3}
        ldmia   ip!, {r0, r1, r2, r3}
        add     ip, sp, #32
        mov     r6, ip
        stmia   r6!, {r0, r1, r2, r3}
        ldmia   r4, {r0, r1, r2, r3}
        stmia   r6, {r0, r1, r2, r3}
        ldmia   ip!, {r0, r1, r2, r3}
        mov     r4, sp
        stmia   r4!, {r0, r1, r2, r3}
        ldmia   r6, {r0, r1, r2, r3}
        stmia   r4, {r0, r1, r2, r3}
        vldmia  sp, {d16-d19}
        vst4.8  {d16-d19}, [r5]
        add     sp, sp, #132
        ldmfd   sp!, {r4, r5, r6}
        bx      lr

Compile flags used were "-mfloat-abi=softfp -mfpu=neon -O3".


-- 
           Summary: vld4 and vst4 intrinsics are not handled correctly
           Product: gcc
           Version: 4.4.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: samuel dot rodal at nokia dot com
 GCC build triplet: arm-none-linux-gnueabi-gcc
  GCC host triplet: arm-none-linux-gnueabi-gcc
GCC target triplet: arm-none-linux-gnueabi-gcc


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43118

[Bug target/43118] vld4 and vst4 intrinsics are not handled correctly

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2010-02-19 11:08 -------
Likely because of the union in

__extension__ static __inline void __attribute__ ((__always_inline__))
vst4_u8 (uint8_t * __a, uint8x8x4_t __b)
{
  union { uint8x8x4_t __i; __builtin_neon_oi __o; } __bu = { __b };
  __builtin_neon_vst4v8qi ((__builtin_neon_qi *) __a, __bu.__o);
}

which does copy-initialization of __bu.  Also try GCC 4.5.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43118

[Bug target/43118] vld4 and vst4 intrinsics are not handled correctly

[ramana at gcc dot gnu dot org]

------- Comment #2 from ramana at gcc dot gnu dot org  2010-02-19 13:45 -------
Trunk behaves similarly - I wonder if this is similar to 41021.

Here's what trunk generates. 

        push    {r4, r5, r6, r7}
        vld4.8  {d16-d19}, [r0]
        sub     sp, sp, #96
        mov     r7, r1
        vstmia  sp, {d16-d19}
        mov     r6, sp
        add     r5, sp, #64
        add     ip, sp, #32
        ldmia   r6!, {r0, r1, r2, r3}
        mov     r4, r5
        stmia   r5!, {r0, r1, r2, r3}
        ldmia   r6, {r0, r1, r2, r3}
        stmia   r5, {r0, r1, r2, r3}
        ldmia   r4!, {r0, r1, r2, r3}
        stmia   ip!, {r0, r1, r2, r3}
        ldmia   r4, {r0, r1, r2, r3}
        stmia   ip, {r0, r1, r2, r3}
        add     r3, sp, #32
        vldmia  r3, {d16-d19}
        vst4.8  {d16-d19}, [r7]
        add     sp, sp, #96
        pop     {r4, r5, r6, r7}
        bx      lr


-- 

ramana at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
      Known to fail|                            |4.4.3 4.5.0
   Last reconfirmed|0000-00-00 00:00:00         |2010-02-19 13:45:57
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43118

[Bug target/43118] vld4 and vst4 intrinsics are not handled correctly

[drow at false dot org]

------- Comment #3 from drow at gcc dot gnu dot org  2010-02-22 21:14 -------
Subject: Re:  vld4 and vst4 intrinsics are not handled
 correctly

On Fri, Feb 19, 2010 at 11:08:18AM -0000, rguenth at gcc dot gnu dot org wrote:
> Likely because of the union in
> 
> __extension__ static __inline void __attribute__ ((__always_inline__))
> vst4_u8 (uint8_t * __a, uint8x8x4_t __b)
> {
>   union { uint8x8x4_t __i; __builtin_neon_oi __o; } __bu = { __b };
>   __builtin_neon_vst4v8qi ((__builtin_neon_qi *) __a, __bu.__o);
> }
> 
> which does copy-initialization of __bu.

Right.  FYI, my best idea to date of how to fix this is to convert the
multiple-vector types (like uint8x8x4_t) to builtin types.  At that
point we can use the neon_reinterpret patterns to do the necessary
type punning without involving __builtin_neon_oi and the union.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43118

[Bug target/43118] vld4 and vst4 intrinsics are not handled correctly

[rguenth at gcc dot gnu dot org]

------- Comment #4 from rguenth at gcc dot gnu dot org  2010-02-23 10:42 -------
(In reply to comment #3)
> Subject: Re:  vld4 and vst4 intrinsics are not handled
>  correctly
> 
> On Fri, Feb 19, 2010 at 11:08:18AM -0000, rguenth at gcc dot gnu dot org wrote:
> > Likely because of the union in
> > 
> > __extension__ static __inline void __attribute__ ((__always_inline__))
> > vst4_u8 (uint8_t * __a, uint8x8x4_t __b)
> > {
> >   union { uint8x8x4_t __i; __builtin_neon_oi __o; } __bu = { __b };
> >   __builtin_neon_vst4v8qi ((__builtin_neon_qi *) __a, __bu.__o);
> > }
> > 
> > which does copy-initialization of __bu.
> 
> Right.  FYI, my best idea to date of how to fix this is to convert the
> multiple-vector types (like uint8x8x4_t) to builtin types.  At that
> point we can use the neon_reinterpret patterns to do the necessary
> type punning without involving __builtin_neon_oi and the union.

Ideally we'd be able to get rid of the extra temporary at the tree level.
Value-numbering can in theory do that, but I suppose the testcase at
hand is obfuscated enough to not do it.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43118

[Bug target/43118] vld4 and vst4 intrinsics are not handled correctly

[ramana at gcc dot gnu dot org]

-- 

ramana at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
           Keywords|                            |missed-optimization


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43118

[Bug target/43118] vld4 and vst4 intrinsics are not handled correctly

[justin dot lebar+bug at gmail dot com]

------- Comment #5 from justin dot lebar+bug at gmail dot com  2010-04-28 21:56 -------
Is there a workaround for this, short of writing inline assembly?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43118

[Bug target/43118] vld4 and vst4 intrinsics are not handled correctly

[generalruzzmo at gmail dot com]

------- Comment #6 from generalruzzmo at gmail dot com  2010-09-15 20:54 -------
this bug is bugging me too..


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43118

[Bug target/43118] vld4 and vst4 intrinsics are not handled correctly

[ramana at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43118

Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ramana at gcc dot gnu.org
      Known to fail|                            |

--- Comment #7 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> 2011-07-08 11:57:04 UTC ---
A recent version of 4.6.1 at O1 appears to give me . That would indicate this
is fixed in trunk.

blend4:
    @ args = 0, pretend = 0, frame = 0
    @ frame_needed = 0, uses_anonymous_args = 0
    @ link register save eliminated.
    vld4.8    {d16-d19}, [r0]
    vst4.8    {d16-d19}, [r1]
    bx    lr
    .size    blend4, .-blend4
    .ident    "GCC: (GNU) 4.7.0 20110616 (experimental)"
    .section    .note.GNU-stack,"",%progbits


Ramana

[Bug target/43118] vld4 and vst4 intrinsics are not handled correctly

[rsandifo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43118

rsandifo@gcc.gnu.org <rsandifo at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |rsandifo at gcc dot gnu.org
         Resolution|                            |FIXED

--- Comment #8 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> 2011-07-19 08:41:04 UTC ---
(In reply to comment #7)
> A recent version of 4.6.1 at O1 appears to give me . That would indicate this
> is fixed in trunk.

Yeah, the bug was fixed as part of the load-lanes stuff.
Since it isn't a regression, and since the fix is too
invasive to backport, I hope it's OK to close as fixed.