Re: [Qemu-devel] cvttps2dq, movdq2q, movq2dq incorrect behaviour

[malc <malc@pulsesoft.com>]

On Tue, 20 Jun 2006, Julian Seward wrote:

>> As for cvttps2dq i ran it with interpreter which uses outdated(i.e. non
>> soft-float) conversion routines and it passed, so my guess would be that
>> this is float32_to_int32_round_to_zero vs (int32_t) cast issue.
>
> I had a feeling this is a garbage-in-memory (or regs, or somewhere)
> problem.  Reason is that the wrong results kept changing as I cut
> the full test program down to just the small one I posted.  Can you
> try on a vanilla build of i386-softmmu from cvs?

soft-float was a red herring, translate.c is at fault here (interpreter
does not use it, hence behaved correctly)

translate.c:3009
if (b1 >= 2 && ((b >= 0x50 && b <= 0x5f) ||
                 b == 0xc2)) {
     /* specific case for SSE single instructions */
     if (b1 == 2) {
         /* 32 bit access */
         gen_op_ld_T0_A0[OT_LONG + s->mem_index]();
         gen_op_movl_env_T0(offsetof(CPUX86State,xmm_t0.XMM_L(0)));
     } else {
         /* 64 bit access */
         gen_ldq_env_A0[s->mem_index >> 2](offsetof(CPUX86State,xmm_t0.XMM_D(0)));
     }
} else {
     gen_ldo_env_A0[s->mem_index >> 2](op2_offset);
}

cvttps2dq is 0x5b(b=0x5b) with repn prefix (b1=2) the above code is optimized
a bit more than it should have been, as it loads only 4 bytes into xmm_t0
instead of 16.

--
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