On Tue, 2009-08-04 at 11:09 +0530, Mohamed Shafi wrote: > >> i am not able to implement the alignment for short. > >> The following is are the macros that i used for this > >> #define PARM_BOUNDARY 8 > >> #define STACK_BOUNDARY 64 > The target is 32bit . The first two parameters are passed in registers > and the rest in stack. For the parameters that are passed in stack the > alignment is that of the data type. The stack pointer is 8 byte > aligned. char is 1 byte, int is 4 byte and short is 2 byte. The code > that is getting generated is give below (-O0 -fomit-frame-pointer)
Er, wait. You set PARM_BOUNDARY to 8. This means all arguments will be padded to at most an 8-bit boundary, which means that yes, a short after a char will have only 1 byte alignment. If you want all arguments to have 2-byte alignment, then you need to set PARM_BOUNDARY to 16. But you probably want a value of 32 here so that 4-byte ints get 4-byte alignment. This will allocate a minimum 4-byte stack slot for every argument. I don't know the calling convention, so I don't know exactly how you want arguments arranged on the stack. If you are pushing arguments, then you can lie in the PUSH_ROUNDING macro. You could say for instance that one byte pushes always push 2 bytes. This ensures that the stack always has 2-byte alignment while pushing arguments. If your push instruction doesn't actually do this, then you need to modify the pushqi pattern to emit two pushes or use a HImode push to get the right behaviour. Try looking at the code in store_one_arg in calls.c, and emit_push_insn in expr.c. Jim
