Consider the following line of the attached test case, where a is double with
value 4294967296.0.
double b = (unsigned int)((unsigned long long int)a % 4294967296ULL);
Then (unsigned long long int)a % 4294967296ULL should be equal to 0ULL, and
therefore b should be 0.0. However, when compiled with -O1 -march=pentium4, b
gets the wrong value of 4294967296.0 (the same as a). Note that the error only
occurs with -march=pentium4.
To compile the testcase:
gcc -std=c99 -O1 -march=pentium4 convert-bug.i -o convert-bug
gcc -v:
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: ../gcc/configure --enable-checking=release
--prefix=/home/jdemeyer/local CC=gcc-4.1.2
Thread model: posix
gcc version 4.4.0 20080916 (experimental) (GCC)
--
Summary: Conversion double -> unsigned long long -> unsigned ->
double gives wrong results
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: jdemeyer at cage dot ugent dot be
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37544
