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

[malc <malc@pulsesoft.com>]

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On Tue, 20 Jun 2006, Julian Seward wrote:

>
> The SSE2 instructions cvttps2dq, movdq2q, movq2dq do not behave
> correctly, as shown by the attached program.  It should print
>
>  cvttps2dq_1 ... ok
>  cvttps2dq_2 ... ok
>  movdq2q_1 ... ok
>  movq2dq_1 ... ok
>
> but instead produces
>
>  cvttps2dq_1 ... ok
>  cvttps2dq_2 ... not ok
>    result0.sd[0] = 12 (expected 12)
>    result0.sd[1] = 3 (expected 56)
>    result0.sd[2] = -2147483648 (expected 43)
>    result0.sd[3] = 3 (expected 87)
>  movdq2q_1 ... not ok
>    result0.uq[0] = 1302123111658042420 (expected 5124095577148911)
>  movq2dq_1 ... not ok
>    result0.uq[0] = 1302123111658042420 (expected 5124095577148911)
>    result0.uq[1] = 6221254864647256184 (expected 0)
>
> I looked at QEMU's instruction decoders for these, and compared them
> to Valgrind's, but could not see what the problem was.  The decode
> logic looks OK.  Maybe the problem is elsewhere.

The signature of movdq2q is Pq, VRq and for movq2dq - Vo, PRq it appears
that translate.c gets it backwards, attached patch should deal with it.

As for cvttps2dq i ran it with interpreter which uses outdated(i.e. non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.

--
mailto:malc@pulsesoft.com

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--- translate.c	Tue Jun 20 15:19:01 2006
+++ /mnt/big/npf/cvs/qemux/qemu/target-i386/translate.c	Tue Jun 20 15:19:20 2006
@@ -2947,15 +2947,15 @@
         case 0x2d6: /* movq2dq */
             gen_op_enter_mmx();
             rm = (modrm & 7) | REX_B(s);
-            gen_op_movq(offsetof(CPUX86State,xmm_regs[reg & 7].XMM_Q(0)),
-                        offsetof(CPUX86State,fpregs[rm].mmx));
-            gen_op_movq_env_0(offsetof(CPUX86State,xmm_regs[reg & 7].XMM_Q(1)));
+            gen_op_movq(offsetof(CPUX86State,xmm_regs[rm].XMM_Q(0)),
+                        offsetof(CPUX86State,fpregs[reg & 7].mmx));
+            gen_op_movq_env_0(offsetof(CPUX86State,xmm_regs[rm].XMM_Q(1)));
             break;
         case 0x3d6: /* movdq2q */
             gen_op_enter_mmx();
             rm = (modrm & 7);
-            gen_op_movq(offsetof(CPUX86State,fpregs[reg].mmx),
-                        offsetof(CPUX86State,xmm_regs[rm].XMM_Q(0)));
+            gen_op_movq(offsetof(CPUX86State,fpregs[rm].mmx),
+                        offsetof(CPUX86State,xmm_regs[reg].XMM_Q(0)));
             break;
         case 0xd7: /* pmovmskb */
         case 0x1d7: