Reload bug

[Jan Hubicka]

> > Concerning this testcase, the reload used to manage to get around this
> > problem.  It didn't get around intentionally and just because the
> > instruction contrain does not accept SSE register so reload is needed
> > anyway.
> 
> I think you're completely right: the reload pass has no specific 
> infrastructure for dealing with invalid subregs. It may "fix" these subregs, 
> but only if it happens that the operand needs reloading because of the insn 
> constraints.
> 
> I now have an example: PR target/10286
> 
> We pass
> 
> (insn 33 30 35 (set (subreg:SI (reg/v:DI 67) 4)
>         (mem/f:SI (plus:SI (reg/f:SI 16 argp)
>                 (const_int 4 [0x4])) [0 hi+0 S4 A32])) 45 {*movsi_1} 
> (insn_list 30 (nil))
> 
> to reload, which produces
> 
> (insn 33 30 35 (set (reg:SI 29 emm0)
>         (mem/f:SI (plus:SI (reg/f:SI 6 ebp)
>                 (const_int 12 [0xc])) [0 hi+0 S4 A32])) 45 {*movsi_1} 
> (insn_list 30 (nil))
>     (nil))
> 
> that is, the only reload for insn 33 is
> 
> Reloads for insn # 33
> Reload 0: reload_in (SI) = (mem/f:SI (plus:SI (reg/f:SI 6 ebp)
>                                                         (const_int 12 [0xc])) 
> [0 hi+0 S4 A32])
> 	GENERAL_REGS, RELOAD_FOR_INPUT (opnum = 1), optional
> 	reload_in_reg: (mem/f:SI (plus:SI (reg/f:SI 6 ebp)
>                                                         (const_int 12 [0xc])) 
> [0 hi+0 S4 A32])
> 
> 
> Incidentally, PR target/10286 is a regression from GCC 3.2 present in
> GCC 3.2.1 and later. The culprit is this patch:
> 
> Sat Oct 19 15:49:14 CEST 2002  Jan Hubicka  <jh@suse.cz>
> 
> 	* mmintrin.h (__m64): typedef it to v2si.
> 	(_mm_cvtsi32_si64, _mm_cvtsi32_si64_mm_sll_pi16,
> 	_mm_sll_pi32, _mm_sll_pi64, _mm_slli_pi64, _mm_sra_pi16,
> 	_mm_sra_pi32, _mm_srl_pi16, _mm_srl_pi32, _mm_srl_pi64,
> 	_mm_srli_pi64, _mm_and_si64, _mm_andnot_si64,
> 	_mm_or_si64, _mm_xor_si64): Add neccesary casts.
> 	* xmmintrin.h (_mm_setzero_si64): Likewise.
> 
> See http://gcc.gnu.org/ml/gcc-patches/2002-10/msg01091.html
> 
> Before the patch, __m64 was defined as 'unsigned long long' so (%eax, %edx) 
> was used instead of %rmm0 and we didn't produce invalid subregs. I think 
> this patch has opened a can of worms and the MMX intrinsics are seriously 
> broken on the 3.2 branch now.

They always have been - I've fixed 50+ different bugs exposed by simple
testsuite executing each individual intrincisc with few diferent args,
so I would not brother about this on the 3.2.  3.3 is different issue
and should be the first GCC where intrincisc are generaly usable.  I
hope.

Will look into this in the detail this evening, now I have about -10
minutes of time.  Thanks!

Honza
> 
> -- 
> Eric Botcazou