On Wed, 2007-01-10 at 15:30 -0800, Ian Lance Taylor wrote:
> Greg Smith <gsmith@xxxxxxxxx> writes:
>
> > [ 7] movl %edx, 24(%esp)
> > [ 8] movl %eax, 28(%esp)
> > #APP
> > bswap %eax
> > #NO_APP
>
> This makes it look like the bswap asm clobbered %edx.
>
> Can you post a small complete standalone preprocessed test case? It's
> quite difficult to analyze an incomplete one. Thanks.
>
Thanks for the quick response!!
The test case below may not be as small as you want, but it does show a
couple (but not all) of the issues.
typedef unsigned char BYTE;
typedef unsigned long U32;
typedef unsigned long long U64;
#define my_bswap_32(x) \
(__extension__ \
({ register unsigned int __v, __x = (x); \
__asm__ ("bswap %0" : "=r" (__v) : "0" (__x)); \
__v; }))
struct REGS {
U64 gr[16];
U64 amask;
void *ip;
BYTE ilc;
};
typedef struct REGS REGS;
int (__attribute__ (( regparm(2) )) z900_load) (BYTE inst[], REGS *regs)
{
int r1;
int b2;
U64 effective_addr2;
U32 temp = my_bswap_32(*(U32*)inst);
r1 = (temp >> 20) & 0xf;
b2 = (temp >> 16) & 0xf;
effective_addr2 = temp & 0xfff;
if (b2) effective_addr2 += regs->gr[b2];
b2 = (temp >> 12) & 0xf;
if (b2) effective_addr2 += regs->gr[b2];
effective_addr2 &= regs->amask;
regs->ip += 4;
regs->ilc = 4;
if ((effective_addr2 & 3) == 0)
return 1;
return 0;
}
compiled with gcc -O3 -fomit-frame-pointer -fPIC -S testload.c
The assembler:
z900_load:
subl $16, %esp
movl %esi, 4(%esp)
movl %edi, 8(%esp)
xorl %edi, %edi
movl %ebp, 12(%esp)
movl (%eax), %ebp
#APP
bswap %ebp
#NO_APP
movl %ebp, %ecx
movl %ebp, %esi
shrl $16, %ecx
andl $4095, %esi
movl %ecx, %eax
andl $15, %eax
[14] movl %edx, (%esp)
je .L2
[16] movl (%esp), %edx
addl (%edx,%eax,8), %esi
adcl 4(%edx,%eax,8), %edi
.L2:
shrl $12, %ebp
movl %ebp, %eax
andl $15, %eax
je .L4
[23] movl (%esp), %ecx
addl (%ecx,%eax,8), %esi
adcl 4(%ecx,%eax,8), %edi
.L4:
[26] movl (%esp), %ecx
[27] xorl %edx, %edx
andl %edi, %edx
movl 128(%ecx), %eax
addl $4, 136(%ecx)
movb $4, 140(%ecx)
movl 8(%esp), %edi
andl $3, %eax
movl 12(%esp), %ebp
andl %esi, %eax
movl 4(%esp), %esi
orl %edx, %eax
sete %al
addl $16, %esp
movzbl %al, %eax
ret
Original %edx is stacked on line 14 and is reloaded on lines 16, 23 and
26 until it's clobbered in line 27. Line 27 seems to be related to the
fix you've been working on.
Greg Smith
