At Tue, 22 Aug 2006 14:44:44 +0100, Andrew Haley wrote: > Simon Kagstrom writes: > > I'm trying to dyanmically generate different bitpatterns using inline > > assembly depeding on a value is constant or not. I'm using it to issue > > system calls (see http://spel.bth.se/index.php/Cibyl) and avoid > > clobbering registers with constant values. What I'm trying to achieve > > is this: > > > > move a0,v0 # Normal MIPS instruction > > 0000fffd # Argument, is a constant > > 00000020 # Constant 32 > > ffff0001 # System call number 1 > [...] > Trying something simpler, > > #include <stdio.h> > int main() { > printf("%d\n", __builtin_constant_p("Hello!")); > } > > returns 1. Hmm... I tried this example and it seems that this might be a problem with my version of GCC for MIPS. It works fine with Debian/testing GCC 3.3.6, 3.4.6 and 4.1.2 but the MIPS cross compiler (3.4.3) doesn't work. The flags I use to compile are -Wall -mips1 -fno-delayed-branch -Os -fno-pic -mno-abicalls > Can you try expanding your example with gcc -E, and paste the result > here so I can try it? Then we'll have a test case we can use. I've attached it below. The code is slightly changed but the result is the same. I now do #define __emit_parameter(x) \ if (__builtin_constant_p(x)) { \ __asm__ volatile ( \ ".long 0xfffd0000\n" \ ".long %0\n" \ : \ : "i,!r"(x) \ ); \ } \ else { \ __asm__ volatile ( \ ".short 0xfffe\n" \ ".short %0\n" \ : \ : "r"(x) \ ); \ } #define _syscall1(type,name,atype,a) \ type name(atype a) \ { \ register unsigned long __v0 asm("$2"); \ \ __asm__ volatile (".set push\n.set noreorder\n"); \ __emit_parameter(a); \ ... but the result is the same. Thanks for looking into this. // Simon
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