unittests/ASM: Adds test to test imul flag calculation

This was incorrect before.

unittests/ASM/FEX_bugs/IMUL_garbagedata_negative.asm

@@ -0,0 +1,100 @@
+%ifdef CONFIG
+{
+  "RegData": {
+    "R15": "0x0000000000003fff"
+  }
+}
+%endif
+
+%macro cfmerge 0
+
+; Get CF
+lahf
+shr rax, 8
+and rax, 1
+
+; Merge in to results
+shl r15, 1
+or r15, rax
+
+%endmacro
+
+; FEX had a bug where imul flag calculation was incorrect.
+; CF and OF are set due to overflow.
+
+mov r15, 0
+mov rax, 0
+
+; Multiply starting value
+mov ebx, 0x6D
+
+; imul 1-src
+mov ebx, 0xaaaaaaab
+mov ecx, 0x6D
+imul cx, bx
+cfmerge
+
+mov ebx, 0xaaaaaaab
+mov ecx, 0x6D
+imul ecx, ebx
+cfmerge
+
+mov rbx, 0xaaaaaaaa_aaaaaaab
+mov rcx, 0x6D
+imul rcx, rbx
+cfmerge
+
+; imul 2-src 8-bit check
+mov ebx, 0xaaaaaaab
+imul cx, bx, 0x6D
+cfmerge
+
+mov ebx, 0xaaaaaaab
+imul ecx, ebx, 0x6D
+cfmerge
+
+mov rbx, 0xaaaaaaaa_aaaaaaab
+imul ecx, ebx, 0x6D
+cfmerge
+
+; imul 2-src 16-bit, 32-bit, 64-bit check
+mov rbx, 0xaaaaaaaa_aaaaaaab
+imul cx, bx, 0x600D
+cfmerge
+
+mov rbx, 0xaaaaaaaa_aaaaaaab
+imul ecx, ebx, 0x600D0000
+cfmerge
+
+
+mov rbx, 0xaaaaaaaa_aaaaaaab
+imul rcx, rbx, 0x600D0000
+cfmerge
+
+mov rbx, 0x0aaaaaaa_aaaaaaab
+imul rcx, rbx, -0x600D0000
+cfmerge
+
+
+; IMUL implicit dest
+mov rax, 0x0aaaaaaa_aaaaaaab
+mov ecx, 0x6D
+imul cl
+cfmerge
+
+mov rax, 0x0aaaaaaa_aaaaaaab
+mov ecx, 0x600D
+imul cx
+cfmerge
+
+mov rax, 0x0aaaaaaa_aaaaaaab
+mov ecx, 0x600D0000
+imul ecx
+cfmerge
+
+mov rax, 0x0aaaaaaa_aaaaaaab
+mov rcx, 0x600D0000_00000000
+imul rcx
+cfmerge
+
+hlt