[x64] Emit vcvtss2sd & vcvtsd2ss when AVX is enabled.

test/cctest/test-assembler-x64.cc

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1342 matching lines @@
     // arguments in xmm0, xmm1 and xmm2
     __ subq(rsp, Immediate(kDoubleSize * 2));  // For memory operand
     __ movl(rax, Immediate(0));
 
     __ vmaxsd(xmm4, xmm0, xmm1);
     __ vmovsd(Operand(rsp, kDoubleSize), xmm4);
     __ vmovsd(xmm5, Operand(rsp, kDoubleSize));
     __ vmovsd(xmm6, xmm5);
     __ vmovapd(xmm3, xmm6);
 
+    // Test vcvtss2sd & vcvtsd2ss
+    __ movl(rax, Immediate(9));
+    __ movq(rdx, V8_INT64_C(0x426D1A0000000000));
+    __ movq(Operand(rsp, 0), rdx);
+    __ vcvtsd2ss(xmm6, xmm6, Operand(rsp, 0));
+    __ vcvtss2sd(xmm7, xmm6, xmm6);
+    __ vcvtsd2ss(xmm8, xmm7, xmm7);
+    __ movss(Operand(rsp, 0), xmm8);
+    __ vcvtss2sd(xmm9, xmm8, Operand(rsp, 0));
+    __ vmovq(rcx, xmm9);
+    __ cmpq(rcx, rdx);
+    __ j(not_equal, &exit);
+
     // Test vcvttsd2si
     __ movl(rax, Immediate(10));
     __ movl(rdx, Immediate(123));
     __ vcvtlsi2sd(xmm6, xmm6, rdx);
     __ vcvttsd2si(rcx, xmm6);
     __ cmpl(rcx, rdx);
     __ j(not_equal, &exit);
     __ xorl(rcx, rcx);
     __ vmovsd(Operand(rsp, 0), xmm6);
     __ vcvttsd2si(rcx, Operand(rsp, 0));
@@ skipping 744 matching lines @@
 
   F1 f = FUNCTION_CAST<F1>(code->entry());
   for (int i = 0; i < kNumCases; ++i) {
     int res = f(i);
     PrintF("f(%d) = %d\n", i, res);
     CHECK_EQ(values[i], res);
   }
 }
 
 #undef __