Extends cvtsi2ss unit test to ensure 32bit correctness

This puts some data in the upper 32bits and makes the number negative to
see if the code gets translated incorrectly.
The x86 JIT currently hits this

unittests/ASM/REP/F3_2A.asm

@@ -4,7 +4,9 @@
     "XMM0":  ["0x414243443f800000", "0x5152535455565758"],
     "XMM1":  ["0x4142434440000000", "0x5152535455565758"],
     "XMM2":  ["0x4142434440400000", "0x5152535455565758"],
-    "XMM3":  ["0x4142434440800000", "0x5152535455565758"]
+    "XMM3":  ["0x4142434440800000", "0x5152535455565758"],
+    "XMM4":  ["0x41424344C0800000", "0x5152535455565758"],
+    "XMM5":  ["0x41424344C0800000", "0x5152535455565758"]
   },
   "MemoryRegions": {
     "0x100000000": "4096"
@@ -28,10 +30,16 @@ mov [rdx + 8 * 4], rax
 mov rax, 0x4
 mov [rdx + 8 * 5], rax
 
+; Stick something in the top 32bits to ensure correctness
+mov rax, 0x7fc00000FFFFFFFC
+mov [rdx + 8 * 6], rax
+
 movapd xmm0, [rdx + 8 * 0]
 movapd xmm1, [rdx + 8 * 0]
 movapd xmm2, [rdx + 8 * 0]
 movapd xmm3, [rdx + 8 * 0]
+movapd xmm4, [rdx + 8 * 0]
+movapd xmm5, [rdx + 8 * 0]
 
 mov rax, [rdx + 8 * 2]
 mov rbx, [rdx + 8 * 3]
@@ -42,4 +50,9 @@ cvtsi2ss xmm1, ebx
 cvtsi2ss xmm2, dword [rdx + 8 * 4]
 cvtsi2ss xmm3, qword [rdx + 8 * 5]
 
+mov rbx, [rdx + 8 * 6]
+
+cvtsi2ss xmm4, ebx
+cvtsi2ss xmm5, dword [rdx + 8 * 6]
+
 hlt