Simon Kagstrom writes: > 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. I see this: static inline int puts (const char *string) { register unsigned long __v0 asm ("$2"); __asm__ volatile (".set push\n.set noreorder\n"); if (__builtin_constant_p (string)) { __asm__ volatile (".long 0xfffd0000\n" ".long %0\n"::"i,!r" (string)); } else { __asm__ volatile (".short 0xfffe\n" ".short %0\n"::"r" (string)); }; __asm__ volatile (".short 0xffff\t#" "puts" "\n\t" ".short %1\n":"=&r" (__v0):"i" (1)); __asm__ volatile (".set\tpop\n"); return (int) __v0; }; and it's pretty clear that string is not a constant in the context of this function: it's a parameter. Andrew.
