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ASM: Another sign extend bug in #3421 #3471

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merged 1 commit into from
Mar 1, 2024
Merged

ASM: Another sign extend bug in #3421 #3471

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17 changes: 15 additions & 2 deletions unittests/32Bit_ASM/FEX_bugs/SignExtendBug.asm
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Original file line number Diff line number Diff line change
Expand Up @@ -2,13 +2,16 @@
{
"RegData": {
"RAX": "0x41424344",
"RBX": "0x41424344"
"RBX": "0x41424344",
"RCX": "0x51525354"
},
"MemoryRegions": {
"0x00fd0000": "4096",
"0xf0000000": "4096"
},
"MemoryData": {
"0xf0000000": "0x41424344"
"0xf0000000": "0x41424344",
"0x00fd0000": "0x51525354"
},
"Mode": "32BIT"
}
Expand All @@ -27,4 +30,14 @@ jmp .test
.test:
mov ebx, [ebx+ecx]

; Ensures that zext occurs correctly with SIB indexing with second argument not having sign bit set but "index" having sign bit.
; Originally saw in Metal Gear Rising Revengeance with a `jmp dword [ecx*4+0xfdbf10]` instruction.
; With ecx = 0xfffffff4 = -12. This is them loading a switch table's branches just before the switch base.
mov ecx, -12

; Break the block so it can't optimize through.
jmp .test2
.test2:

mov ecx, [ecx*4+0x00fd_0030]
hlt
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