Changes between Version 6 and Version 7 of TBR/UserManual/Floating_Point_Support


Ignore:
Timestamp:
Jul 12, 2009, 5:38:17 AM (10 years ago)
Author:
Kptrs
Comment:

Legend:

Unmodified
Added
Removed
Modified
  • TBR/UserManual/Floating_Point_Support

    v6 v7  
    8888
    8989
     90Technically I should probably call this "cpukit support" rather than "BSP support." However, since often someone looking into a board port needs to at least look at the CPU support, and possibly adjust it, I am considering the cpukit as part of the "greater BSP".
     91
    9092The definitions controlling floating point support for the RTEMS kernel are found in a CPU-dependent header file in the RTEMS source tree, typically {{{cpukit/score/cpu/<cpu name>/rtems/score/cpu.h</code>.
    9193
     
    118120
    119121In theory, the determination of whether the CPU has a hardware FPU should be made based on knowledge of which CPU is involved. In practice, the determination is commonly made based on a definition set by the compiler based on compiler command line arguments such as -msoft-float (in the example above, if that compiler option is provided, then the SPARC cross-compiler automatically sets the preprocessor definition {{{_SOFT_FLOAT</code>). '''<big>This is often a mistake,</big>''' because there are other reasons for telling the compiler to use software floating point besides absence of a hardware FPU (see below).
     122
     123In addition to the preprocessor definitions for floating point settings, the BSP must provide the actual functions for various operations such as saving and restoring the floating point context, since they are CPU dependent. These are typically found in {{{cpukit/score/cpu/<cpu name>/cpu_asm.S</code>.
    120124= Compiler Support =