On Sun, 2008-04-20 at 11:16 -0700, Brian Dessent wrote: > The stack pointer is always kept aligned to 16 bytes so that functions > that require it (e.g. those that use SIMD operands) don't have to emit > instructions to align it in the prologue. > > Brian That's what I thought. But notice the prologue: main: pushq %rbp movq %rsp, %rbp subq $88, %rsp Now the stack pointer is not on a 16-byte boundary. Reading the ABI carefully (n+1 times), I see that it says that the 16-byte boundary for the stack is the condition upon entry to a function. The easiest way to do this is to allocate local variable space in multiples of 16 in the prologue. Since this function does not call a function, my take is that the 16-byte rule does not apply. I ran this in gdb, and sure enough, the stack pointer is at an 8-byte boundary, not 16-byte. -- Bob
