We noticed that the simple loop here
extern int a[];
int foo(int w) {
int n = w;
while (n >= 512)
{
a[n] = 42;
n -= 256;
}
}
was being treated as ineligible for the doloop modification. I think
this is
a simple pasto; this code was evidently copied from the previous block:
Index: loop-iv.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/loop-iv.c,v
retrieving revision 2.35
diff -u -b -c -p -r2.35 loop-iv.c
cvs diff: conflicting specifications of output style
*** loop-iv.c 21 Jul 2005 07:24:07 -0000 2.35
--- loop-iv.c 29 Aug 2005 23:34:12 -0000
*************** iv_number_of_iterations (struct loop *lo
*** 2417,2423 ****
tmp0 = lowpart_subreg (mode, iv0.base, comp_mode);
tmp1 = lowpart_subreg (mode, iv1.base, comp_mode);
! bound = simplify_gen_binary (MINUS, mode, mode_mmin,
lowpart_subreg (mode, step, comp_mode));
if (step_is_pow2)
{
--- 2417,2423 ----
tmp0 = lowpart_subreg (mode, iv0.base, comp_mode);
tmp1 = lowpart_subreg (mode, iv1.base, comp_mode);
! bound = simplify_gen_binary (PLUS, mode, mode_mmin,
lowpart_subreg (mode, step, comp_mode));
if (step_is_pow2)
{
The code as it was computed -2147483648-256 which overflows.
Still testing, but is there anything obvious wrong with this?
