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.
Is there any documentation about __asm__ default behavior regarding this issue? Something like an Intel/AMD/AT&T manual explaining this? 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.
