[Nasm-bugs] [Bug 3392788] New: Missing size optimization in mov [ebp + ecx]
noreply-nasm at dev.nasm.us
noreply-nasm at dev.nasm.us
Wed Nov 24 04:28:39 PST 2021
https://bugzilla.nasm.us/show_bug.cgi?id=3392788
Bug ID: 3392788
Summary: Missing size optimization in mov [ebp + ecx]
Product: NASM
Version: 2.15.xx
Hardware: PC
OS: Linux
Status: OPEN
Severity: normal
Priority: Medium
Component: Assembler
Assignee: nobody at nasm.us
Reporter: negge at dgql.org
CC: chang.seok.bae at intel.com, gorcunov at gmail.com,
hpa at zytor.com, nasm-bugs at nasm.us
Obtained from: From OS distribution
I was surprised to see that nasm did not output the smaller, equivalent
instruction when assembling mov [ebp + ecx]. The following two are semantically
the same, but mov [ecx + ebp] is one byte smaller.
$ cat mov.asm
BITS 32
mov ch, [ecx + ebp]
mov ch, [ebp + ecx]
$ nasm mov.asm -o mov.bin
$ ndisasm -b32 mov.bin
00000000 8A2C29 mov ch,[ecx+ebp]
00000003 8A6C0D00 mov ch,[ebp+ecx+0x0]
I am running gentoo and compiled this from source using the OS package manager
portage:
# genlop nasm
* dev-lang/nasm
Sun Mar 21 12:43:05 2021 >>> dev-lang/nasm-2.15.05
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