gcc-2.95/v850 : bug in interrupt handlers

[Matteo Frigo]

Dear gcc maintainers,

     First of all, thanks for producing and supporting gcc and the
excellent GNU development tools.  This email is to notify you that
gcc-2.95/v850 produces incorrect code when compiling interrupt
handlers.  I am running gcc-2.95 on RedHat linux 6.0.  I configured
the compiler with ./configure --target=v850.

The following program demonstrates the bug:

int k;
void __attribute__((interrupt)) foo(void)
{
     int i, x=0;
     for (i = 0; i < 100; ++i) 
	   x |= i;
     k = x;
}

When compiled with
  /scratch/v850/gcc-2.95/gcc/xgcc -B/scratch/v850/gcc-2.95/gcc/ -O -S foo.c
I obtain the following output:

	.file	"foo.c"
gcc2_compiled.:
	.section .text
	.align 1
	.global _foo
	.type	 _foo,@function
_foo:
	add -16,sp
	st.w r10,12[sp]
	jarl __save_interrupt,r10
	add -8,sp
	st.w r11,4[sp]
	st.w r12,0[sp]
	mov 0,r12
	mov 0,r10
	movea lo(99),r0,r11
.L6:
	or r10,r12
	add 1,r10
	cmp r11,r10
	ble .L6
	movhi hi(_k),r0,r10
	st.w r12,lo(_k)[r10]
	add 8,sp             	#***** BUG *****
	ld.w 4[sp],r11
	ld.w 0[sp],r12
	add 8,sp                #***** add 8,sp is done twice *****
	jr __return_interrupt
.Lfe1:
	.size	 _foo,.Lfe1-_foo
	.comm	_k,4,4
	.ident	"GCC: (GNU) 2.95 19990728 (release)"

As can be seen, the compiler adds 8 twice to the stack pointer.  
This behavior is incorrect because 1) sp is not restored to the
original value at the end of __return_interrupt and 2) r11 and
r12 are restored to bogus values.  If the first instruction
``add 8,sp'' is removed, the resulting code is correct.

Regards,
Matteo Frigo