-O3 optimization level makes more than 20% tests failed

[boubalos]

-O3 optimization level makes more than 20% tests failed when compiling CLAPACK-3.1.1.1 using gcc 4.4.

if using optimization level -O0, almost all tests passed.

my make.inc is the same as make.inc.example execpt that I use:
CC = gcc -DNO_BLAS_WRAP
BLASLIB = -lblas -latlas

I am under debian/squeeze, and I use libblas and libatlas provided by squeeze. However I found ubuntu 8.04's gcc-4.2 also has this problem.

What's the reason?