2009/8/5 Jim Wilson <wil...@codesourcery.com>:
> 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.
>
What i did was to define FUNCTION_ARG_BOUNDARY macro to return the
alignment as per the requirement. i.e 8bits for char, 16bits for
short, 32bits for int and kept PARM_BOUNDARY to 8. Now the complier is
emitting the alignment prperly.
Is this OK?
Regards,
Shafi
