MIPS: math-emu: <MADDF|MSUBF>.<D|S>: Fix NaN propagation

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: e24c3bec3e8e ("MIPS: math-emu: Add support for the MIPS R6 MADDF FPU instruction")
Fixes: 83d43305a1df ("MIPS: math-emu: Add support for the MIPS R6 MSUBF FPU instruction")

Signed-off-by: Miodrag Dinic <[email protected]>
Signed-off-by: Goran Ferenc <[email protected]>
Signed-off-by: Aleksandar Markovic <[email protected]>
Reviewed-by: James Hogan <[email protected]>
Cc: Bo Hu <[email protected]>
Cc: Douglas Leung <[email protected]>
Cc: Jin Qian <[email protected]>
Cc: Paul Burton <[email protected]>
Cc: Petar Jovanovic <[email protected]>
Cc: Raghu Gandham <[email protected]>
Cc: <[email protected]> # 4.7+
Cc: [email protected]
Cc: [email protected]
Patchwork: https://patchwork.linux-mips.org/patch/16886/
Signed-off-by: Ralf Baechle <[email protected]>

0 files changed, 0 insertions, 0 deletions