Mathieu Desnoyers wrote:
I have tried generating asm-to-"register" c variables for char, short and int on i386 and I do not see this happening. The char opcode is always 1 byte, short 2 bytes and int 1 byte. Result:
The comment was referring to x86-64, but I incorrectly remembered that applying to "movq $imm,%reg" as opposed to loading from an absolute address. gas actually has a special opcode (movabs) for the 64-bit version of the latter variant, which is only available with %rax and its subregisters.
Nevermind, in other words. It's still true, though, that the immediate will always be the last thing in the instruction -- that's a fixture of the instruction format.
gcc version 4.1.3 20070812 (prerelease) (Debian 4.1.2-15) 8: b3 02 mov $0x2,%bl a: b1 03 mov $0x3,%cl c: b2 04 mov $0x4,%dl e: b0 05 mov $0x5,%al 4f: 66 be 06 00 mov $0x6,%si 53: 66 bb 07 00 mov $0x7,%bx 57: 66 b9 08 00 mov $0x8,%cx 5b: 66 ba 09 00 mov $0x9,%dx 5f: 66 b8 0a 00 mov $0xa,%ax 9f: bb 0b 00 00 00 mov $0xb,%ebx a4: be 0c 00 00 00 mov $0xc,%esi a9: b9 0d 00 00 00 mov $0xd,%ecx ae: ba 0e 00 00 00 mov $0xe,%edx b3: b8 0f 00 00 00 mov $0xf,%eax I notice that having a "=r" inline assembly that outputs to the first "register char" variable seems to be problematic. It fails with the following error: /tmp/ccy35Hq1.s: Assembler messages: /tmp/ccy35Hq1.s:15: Error: bad register name `%sil'
'r' is wrong for 8-bit variables on i386. It needs to be 'q'. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
