[Bug target/44364] Wrong code with e500 double floating point

["Kyle dot D dot Moffett at boeing dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #4 from Kyle dot D dot Moffett at boeing dot com  2010-06-03 20:09 -------
Ok, I have a trivial 19-line testcase that triggers the bug on my native Debian
GCC 4.4.4-2+powerpcspe1 (with PR44169 fix) with -O0 and -O3.  The compiler was
built with: --with-cpu=8548 --enable-e500_double --with-long-double-128
  In order to make it work on -O3 I had to split the "double z", "void
problem()" and "int main()" into 3 separate files to prevent GCC from inlining
everything.

Compiled with:
  gcc -Wall -Wextra -Werror -ggdb3 -O0 -o testall testall.c
Output (the two "main: a" lines should read the same):
  main: a = 78.463000
  problem: a = 39.231500
  main: a = 39.231476

Or with:
  gcc -Wall -Wextra -Werror -ggdb3 -O3 -o test.o -c test.c
  gcc -Wall -Wextra -Werror -ggdb3 -O3 -o test2.o -c test2.c
  gcc -Wall -Wextra -Werror -ggdb3 -O3 -o test3.o -c test3.c
  gcc -Wall -Wextra -Werror -ggdb3 -O3 -o test test.o test2.o test3.o
Output:  (again, "main" lines should be identical)
  main: a = 78.463000
  problem: a = 39.231500
  main: a = 78.462952

As you might imagine, a bug this bad triggers testsuite failures in MPFR, GMP,
PostgreSQL, lapack, and basically everything else with a comprehensive
floating-point test-suite.

Cheers,
Kyle Moffett


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44364