[Nasm-bugs] [Bug 3392467] New: use short immediate opcode when available
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Fri Feb 23 12:26:11 PST 2018
https://bugzilla.nasm.us/show_bug.cgi?id=3392467
Bug ID: 3392467
Summary: use short immediate opcode when available
Product: NASM
Version: 2.12.xx
Hardware: All
OS: Linux
Status: OPEN
Severity: normal
Priority: Medium
Component: Assembler
Assignee: nobody at nasm.us
Reporter: negge at dgql.org
CC: gorcunov at gmail.com, hpa at zytor.com, nasm-bugs at nasm.us
Obtained from: From OS distribution
Created attachment 411626
--> https://bugzilla.nasm.us/attachment.cgi?id=411626&action=edit
nasm_bug.asm
Some opcodes allow byte immediate's when they value is -128 to 127. However,
if that value is defined with arithmetic, the assembler picks the larger size.
See the following example:
$ cat nasm_bug.asm
bits 16
org 0x100
segment .text
jmp @end_data
val1: dw 0x1234
@end_data:
fild word [si + 0x2]
fild word [si + val1 - 0x100]
ret
$ ndisasm -b16 nasm_bug.com
00000000 EB02 jmp short 0x4
00000002 3412 xor al,0x12
00000004 DF4402 fild word [si+0x2]
00000007 DF840200 fild word [si+0x2]
0000000B C3 ret
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