Stack and Function parameters alignment

[Petar Penchev]

Hello All,
The CPU ,I am porting GCC to , has PUSH instruction for half-word (byte)  
and PUSH instruction for word as well.
GCC is using them well, until I was told to add a command-line option  
which allows GCC to align on word.
It has been done, however, there samoe problems. GCC generates following  
code:

PUSH AL ; AL is 8-bit reister
INC S ;	increment stack pointer

This is correct code, but it is longer than

PUSH A ; where A is 16 bit register

And if RAM does not allow access on ODD addresses.

I have define following macros as follows

/ *tm.h */
#define PARM_BOUNDARY		(TARGET_STACK_BYTE_ALLIGN?BITS_PER_WORD / 2:  
BITS_PER_WORD)
#define STACK_BOUNDARY		((TARGET_STACK_BYTE_ALLIGN?BITS_PER_WORD / 2:  
BITS_PER_WORD))
/***/

In .md file  have defined

(define_expand "pushqi"
[
  (set (mem:QI (post_inc (reg:HI S_HREG)))
	  (match_operand:QI 0 "general_operand" "")
  )
]
""
""
)

(define_insn "*pushqi"
   [(set (mem:QI (post_inc (reg:HI S_HREG)))
	(match_operand:QI 0 "general_operand" "b"))]
  "TARGET_STACK_BYTE_ALLIGN"
   "push\t%0\t; *pushqi"
   [(set_attr "cc" "none")]
)



(define_insn "*pushqi_word_aligned"
   [(set (mem:QI (post_inc (reg:HI S_HREG)))
	(match_operand:QI 0 "general_operand" "b"))]
   "!TARGET_STACK_BYTE_ALLIGN"
   "#"
   [(set_attr "cc" "none")]
)

(define_split
  [(set (mem:QI (post_inc (reg:HI S_HREG)))
	(match_operand:QI 0 "general_operand" "b"))]
   "!TARGET_STACK_BYTE_ALLIGN"
  [
    (set (match_dup 1)
		(match_dup 0)
    )
    (set (mem:HI (post_inc (reg:HI S_HREG)))
		(match_dup 1)
    )
  ]
   "
   operands[1] = gen_rtx(REG, HImode, A_HREG);
   "
)

The asm code I expect this RTL to generate is
PUSH A

BUT instead of that it generates

PUSH A ; stack is even
INC S ; incorrect (the stack is ODD)

What am I doing wrong ? Can somebody tell me how to solve this problem ?



Regards
Petar Penchev
Software engineer