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

[malc <malc@pulsesoft.com>]

On Wed, 21 Jun 2006, Julian Seward wrote:

>
> Malc, your sse-movq.patch works for me.  Thanks.
>
>> 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.
>
> Uh, fine, but I don't understand how/what to fix.  Can you advise?

Following will fix the _specific_ case of cvttps2dq, ideally one
should go through all the [0x50..0x5f, 0xc2] with (repnz,repz prefix)
range and check wether the rules imposed by the above snippet apply.

--- /mnt/big/npf/cvs/qemux/qemu/target-i386/translate.c Tue Jun 20 15:19:20 2006
+++ translate.c Tue Jun 20 18:17:19 2006
@@ -3009,7 +3009,9 @@
                  if (b1 >= 2 && ((b >= 0x50 && b <= 0x5f) ||
                                  b == 0xc2)) {
                      /* specific case for SSE single instructions */
-                    if (b1 == 2) {
+                    if (b1 == 2 && b == 0x5b) {
+                        gen_ldo_env_A0[s->mem_index >> 2](offsetof(CPUX86State,xmm_t0.XMM_Q(0)));
+                    } else 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)));

-- 
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