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Date: Thu, 01 May 2003 13:39:53 +0800
From: Fuxin Zhang <fxzhang@ict.ac.cn>
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To: MAKE FUN PRANK CALLS <linux-mips@linux-mips.org>, gcc@gcc.gnu.org
Subject: GCC -O2 failure for mipsel
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Hello,
I've met a case where mipsel-linux-gcc -O2 fails,for both
2.96 and the fresh new 3.2.3. Maybe someone can tell me
what's wrong.

I've reduced the problem to the test case below,compile it
with mipsel-linux-gcc -O2(FROM H.J.Lu's redhat miniport,all version,
and 3.2.3 is tested too)


#define PUT_CODE(x,code) ((x)->code = (code))
union test_union {
struct test *t;
int a;
};

struct test {
unsigned short code;
union test_union u[1];
};

char memory[2000];

struct test *test_alloc(int code)
{
struct test *t;
int length=sizeof(struct test);

t = (struct test*)memory;
length = (sizeof(struct test) - sizeof(union test_union)-1)/sizeof(int);
for (;length>=0;length--)
((int*)t)[length] = 0;

PUT_CODE(t,code);

return t;
}

int main()
{
struct test *t;

t = test_alloc(4);

printf("t->code=%d\n",t->code);
}


Problem happens in test_alloc:

00400890 <test_alloc>:
400890: 3c1c0fc0 lui gp,0xfc0
400894: 279c77b0 addiu gp,gp,30640
400898: 0399e021 addu gp,gp,t9
40089c: 8f828054 lw v0,-32684(gp)
4008a0: 8f818054 lw at,-32684(gp)
4008a4: 00000000 nop
4008a8: a4240000 sh a0,0(at)
4008ac: 03e00008 jr ra
4008b0: ac400000 sw zero,0(v0)
--->the last sw is wrong,it should not be reorder to run later than 4008a8.

And gcc experts will find this is a simplfied case of rtx_alloc:).
Yes,the failure
shows up when i try to compile SPEC CPU2000 176.gcc with -O2. The const0_rtx
's code will be set to zero like above.

Thank you in advance.


Regards