• Aleksandar Markovic's avatar
    MIPS: math-emu: <MADDF|MSUBF>.<D|S>: Fix NaN propagation · e840be6e
    Aleksandar Markovic authored
    Fix the cases of <MADDF|MSUBF>.<D|S> when any of three inputs is any
    NaN. Correct behavior of <MADDF|MSUBF>.<D|S> fd, fs, ft is following:
    
      - if any of inputs is sNaN, return a sNaN using following rules: if
        only one input is sNaN, return that one; if more than one input is
        sNaN, order of precedence for return value is fd, fs, ft
      - if no input is sNaN, but at least one of inputs is qNaN, return a
        qNaN using following rules: if only one input is qNaN, return that
        one; if more than one input is qNaN, order of precedence for
        return value is fd, fs, ft
    
    The previous code contained correct handling of some above cases, but
    not all. Also, such handling was scattered into various cases of
    "switch (CLPAIR(xc, yc))" statement, and elsewhere. With this patch,
    this logic is placed in one place, and "switch (CLPAIR(xc, yc))" is
    significantly simplified.
    
    A relevant example:
    
    MADDF.S fd,fs,ft:
      If fs contains qNaN1, ft contains qNaN2, and fd contains qNaN3, fd
      is going to contain qNaN3 (without this patch, it used to contain
      qNaN1).
    
    Fixes: e24c3bec ("MIPS: math-emu: Add support for the MIPS R6 MADDF FPU instruction")
    Fixes: 83d43305 ("MIPS: math-emu: Add support for the MIPS R6 MSUBF FPU instruction")
    Signed-off-by: default avatarMiodrag Dinic <miodrag.dinic@imgtec.com>
    Signed-off-by: default avatarGoran Ferenc <goran.ferenc@imgtec.com>
    Signed-off-by: default avatarAleksandar Markovic <aleksandar.markovic@imgtec.com>
    Reviewed-by: default avatarJames Hogan <james.hogan@imgtec.com>
    Cc: Bo Hu <bohu@google.com>
    Cc: Douglas Leung <douglas.leung@imgtec.com>
    Cc: Jin Qian <jinqian@google.com>
    Cc: Paul Burton <paul.burton@imgtec.com>
    Cc: Petar Jovanovic <petar.jovanovic@imgtec.com>
    Cc: Raghu Gandham <raghu.gandham@imgtec.com>
    Cc: <stable@vger.kernel.org> # 4.7+
    Cc: linux-mips@linux-mips.org
    Cc: linux-kernel@vger.kernel.org
    Patchwork: https://patchwork.linux-mips.org/patch/16886/Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
    e840be6e
dp_maddf.c 5.32 KB