[eigen] check for old gcc (inadvertently?) catching intel compiler and disabling SSE

[ Thread Index | Date Index | More lists.tuxfamily.org/eigen Archives ]

in Eigen/Core, there is a check that disables SSE for gcc compilers < 4.2. Unfortunately it gets triggered under the *intel* compiler.

#if (defined __SSE2__) && ( (!defined __GNUC__) || EIGEN_GNUC_AT_LEAST(4,2) )

The intel compiler masquerades by defining __GNUC__ and related version variables to mimic the gcc version installed on the system. The effect in Eigen is that the intel compiler may not get a chance to use SSE even if it can[1].


    [user@centos58-64 ~/]$ gcc --version
    gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-54)

    [user@centos58-64 ~/]$  icpc -dM -E - < /dev/null  |  grep GNUC
    #define __GNUC__ 4
    #define __GNUC_MINOR__ 1
    #define __GNUC_PATCHLEVEL__ 2

Intel compilers at least as recent as 12.1.3 20120212 exhibit this GNUC mimicry.

[1] What is the problem with gcc 4.1 and SIMD? The version check in Eigen seems originate at changeset 246:566b4821dd1b , but I could not easily tell what problem it was fixing. I have some systems still running RedHat 5.x, which has gcc 4.1 as the default compiler. I'd like to support them with Eigen+SIMD on Intel(first choice), and/or platform-default gcc.

-- Mark

Mail converted by MHonArc 2.6.19+ http://listengine.tuxfamily.org/