On Tue, Mar 24, 2009 at 1:18 PM, Rodrigo Dominguez <rodd...@hotmail.com> wrote:
> H.J,
>
> Thanks for replying but this doesn't answer my question. Shouldn't __asm__
> generate the right code without using the %b1 trick? The reason I am asking
> is I have a 350 line macro which I can't change.
Those macros are wrong.
> Is there any documentation about __asm__ default behavior regarding this
> issue? Something like an Intel/AMD/AT&T manual explaining this?
asm statement is compiler specific. It is documented in gcc manual. You
can take a look at *.md in i386 to see how asm statement may be used:
[...@gnu-13 i386]$ grep shr i386.md | grep %b
shr{q}\t{%b2, %0|%0, %b2}"
shr{l}\t{%b2, %0|%0, %b2}"
shr{l}\t{%b2, %k0|%k0, %b2}"
shr{w}\t{%b2, %0|%0, %b2}"
shr{b}\t{%b2, %0|%0, %b2}"
shr{b}\t{%b1, %0|%0, %b1}"
[...@gnu-13 i386]$
H.J.
---
> Thank you,
>
> Rodrigo
>
>> -----Original Message-----
>> From: H.J. Lu [mailto:hjl.to...@gmail.com]
>> Sent: Tuesday, March 24, 2009 2:09 PM
>> To: Rodrigo Dominguez
>> Cc: gcc@gcc.gnu.org
>> Subject: Re: Inline Assembly Error: suffix or operands invalid for
>> 'shr'
>>
>> On Tue, Mar 24, 2009 at 11:02 AM, Rodrigo Dominguez
>> <rodd...@hotmail.com> wrote:
>> > Hi,
>> >
>> > While debugging a problem with Open64, I ran into a similar problem
>> with
>> > GCC. I created the following unit test program:
>> >
>> > #include <stdint.h>
>> >
>> > int main(void)
>> > {
>> > uint32_t a = 7;
>> > int8_t s = -1;
>> >
>> > __asm__ ("shrl %1, %0\n\t"
>> > : "+r" (a)
>> > : "c" (-s)
>> > );
>> >
>> > return a;
>> > }
>> >
>> > When assembling this program, 'cc1' emits a 'shrl %ecx, %eax'
>> instruction.
>> > The 'shr' instruction can only take an 8-bit register as the first
>> operand.
>> > The emitted instruction should have been 'shrl %cl, %eax'. Therefore,
>> the
>> > compilation fails with a 'suffix or operands invalid for shr'
>> message.
>> >
>>
>> Please use
>>
>> __asm__ ("shrl %b1, %0\n\t"
>> : "+r" (a)
>> : "c" (-s)
>> );
>>
>> --
>> H.J.
>
>
--
H.J.
