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numerical instability and estimate-probability
- From: Jan Hubicka <jh at suse dot cz>
- To: gcc at gcc dot gnu dot org, rth at cygnus dot com, gcc-pdo at atrey dot karlin dot mff dot cuni dot cz
- Date: Thu, 15 Nov 2001 15:47:07 +0100
- Subject: numerical instability and estimate-probability
I am getting bootstrap comparison failure in i386 on the cfg-branch now.
It is due to estimate-probability to have off-by-one error when computing
the probability that causes tracer to behave differently.
I am currently solving it by adding volatile to the variable so it is
stored to memory and truncated each time it is seen. Would be such
trick acceptable sollution or do we want to make better? What?
Perhaps it is time to add some arbitary precision number implementation to
gcc tree. I believe it has been discussed previously, but I forgot where.