Simon Kagstrom writes: > Hello! > > 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 > > I use the first word as encoding of the "argument" type and the second > as the constant or register number. My problem is: How can I generate > this reliably from inline assembly? It seems to me that > __builtin_constant_p doesn't work as I would expect it to. Looking at the source of fold_builtin_constant_p(), I see this: if (TREE_CODE (arglist) == ADDR_EXPR) { tree op = TREE_OPERAND (arglist, 0); if (TREE_CODE (op) == STRING_CST || (TREE_CODE (op) == ARRAY_REF && integer_zerop (TREE_OPERAND (op, 1)) && TREE_CODE (TREE_OPERAND (op, 0)) == STRING_CST)) return integer_one_node; } which looks like it ought to work. Trying something simpler, #include <stdio.h> int main() { printf("%d\n", __builtin_constant_p("Hello!")); } returns 1. 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. Andrew.
