http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50599
Bug #: 50599
Summary: -ftree-vectorize generating incorrect code
Classification: Unclassified
Product: gcc
Version: 4.5.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: a5970...@nepwk.com
MinGW x86 4.5.2
A loop:
while(total_out < decompressed_size)
{
printf("%X\n",p);
int chunk_size = *(int*)p;
if(chunk_size > 0)
{
int ret = params->decompressor(p+sizeof(int), chunk_size,
params->out+total_out, std::min(params->osize-total_out,params->bsize),
params->other);
int real_out = (ret / params->ssize) * params->ssize;
if(real_out != ret)
real_out += params->ssize;
if(total_out + real_out >= params->isize)
total_out += ret;
else
total_out += real_out;
p += chunk_size+sizeof(int);
}
else
{
if(params->verify)
{
memcpy(params->out+total_out, p+sizeof(int), -chunk_size);
p += -chunk_size;
}
total_out += -chunk_size;
p += sizeof(int);
}
}
Compiled with -O3 -fno-strict-aliasing works funny - the printf is called twice
with the same address. And on some data I'm getting crashes in
params->decompressor, which is a 3rd party code.
I added other printfs and I see that when running the loop for the 1st time,
the code enters the 1st branch, goes to p += chunk_size+sizeof(int), increases,
goes out of the if and iterates the loop again with unchanged p.
Adding -fno-tree-vectorize solves the problem.
