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Optimization o2 vs o3 issue
- From: Manish Baphna <manish_baphna at yahoo dot com>
- To: gcc-help at gcc dot gnu dot org
- Date: Mon, 15 Dec 2008 13:47:47 +0530 (IST)
- Subject: Optimization o2 vs o3 issue
- Reply-to: manish_baphna at yahoo dot com
Hi,
This is Manish from India and I am facing an issue with g++ 4.1.1. optimization flag '-o3'
"We are running A SW which is combination of new developed code + Standard Inhouse Developed Libraries. I am testing it on two machines , one we have in India and one in US. At both places Developed Code is exactly same , Inhouse Libs are also supposed to be same but there might be very slight variation . Same code base is passing in India for both Debug and Release version . In US , debug version passes but release version fails. Fail means, it compiles and builds but when we run test ,there is
data lose somewhere hence test fails.
We zeroed down issue to these two lines in a CPP
#Line1# dout.data[15 - count] = (uint8_t)(((long long unsigned int)(*(soc_cpr_dbusdataout_->sig_value_upper)) & (mask << ((8+count)*8)))>>((8+count)*8));
#Line2# cout << "Dout data " << (uint64_t)((dout.data)[15-count]) << endl;
In US, if we comment 2nd line in RELEASE build (as we should), it FAILS with -o3 switch. If we put -o2 switch ,it PASSES. We also tried with -finline-functions switch with o2/o3 but it didn't change scene. Unfortunately we use -o3 in our releases. So we are left no option but to have this 'cout' in the code so that it can work.
Seems like its NOT totally unknown issue with GCC4.x family ( we are using gcc4.1.1), some other people Have shared similar griefs.
Also, just to play around we tried replacing second line with some other lines like
cout << "--------------------------------------------------------" << endl;
int temp = (uint64_t)((dout.data)[15-count]) ; (void)temp ;
cout << " Manish Baphna" << (uint64_t)((dout.data)[15-count]) << endl; But nothing worked with -o3. Seems like it wants 'cout' with that particulat typecast statement ( grrrr ... :))
Though we are not stuck due to this , I am keen in finding out the root cause. Also ,are there any other dignified workarounds other then using o2 switch or having cout in release build ?
Best Regards
- Manish
PS : I am not very regular on this list so apologies in case I am cribbing for already discussed issue.
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