Implement fused multiply-add with correct accuracy.

Fused multiply-add operation has better accuracy than respective
sequential execution of multiply and add operations applied on the
same inputs. This is because accuracy errors accumulate in latter
case.

This patch implements fused multiply-add with the same accuracy
as it is implemented in hardware, using 64-bit intermediate
calculations.

One test case example (raw bits) that this patch fixes:

MADDF.S fd,fs,ft:
  fd = 0x22575225
  fs = ft = 0x3727c5ac

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: NDouglas Leung <douglas.leung@imgtec.com>
Signed-off-by: NMiodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: NGoran Ferenc <goran.ferenc@imgtec.com>
Signed-off-by: NAleksandar Markovic <aleksandar.markovic@imgtec.com>
Cc: Douglas Leung <douglas.leung@imgtec.com>
Cc: Bo Hu <bohu@google.com>
Cc: James Hogan <james.hogan@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/16890/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

Fix definition and usage of "maddf_flags" enumeration. Avoid duplicate
definition and apply more common capitalization.

This patch does not change any scenario. It just makes MADDF and
MSUBF emulation code more readable and easier to maintain, and
hopefully prevents future bugs as well.
Signed-off-by: NMiodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: NGoran Ferenc <goran.ferenc@imgtec.com>
Signed-off-by: NAleksandar Markovic <aleksandar.markovic@imgtec.com>
Reviewed-by: NJames 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/16889/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

Fix the cases of <MADDF|MSUBF>.<D|S> when any of two multiplicands is
+0 or -0, and the third input is also +0 or -0. Depending on the signs
of inputs, certain special cases must be handled.

A relevant example:

MADDF.S fd,fs,ft:
  If fs contains +0.0, ft contains -0.0, and fd contains 0.0, fd is
  going to contain +0.0 (without this patch, it used to contain -0.0).

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: NMiodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: NGoran Ferenc <goran.ferenc@imgtec.com>
Signed-off-by: NAleksandar Markovic <aleksandar.markovic@imgtec.com>
Reviewed-by: NJames 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/16888/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

Fix the cases of <MADDF|MSUBF>.<D|S> when any of two multiplicands is
infinity. The correct behavior in such cases is affected by the nature
of third input. Cases of addition of infinities with opposite signs
and subtraction of infinities with same signs may arise and must be
handles separately. Also, the value od flags argument (that determines
whether the instruction is MADDF or MSUBF) affects the outcome.

Relevant examples:

MADDF.S fd,fs,ft:
  If fs contains +inf, ft contains +inf, and fd contains -inf, fd is
  going to contain indef (without this patch, it used to contain
  -inf).

MSUBF.S fd,fs,ft:
  If fs contains +inf, ft contains 1.0, and fd contains +0.0, fd is
  going to contain -inf (without this patch, it used to contain +inf).

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: NDouglas Leung <douglas.leung@imgtec.com>
Signed-off-by: NMiodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: NGoran Ferenc <goran.ferenc@imgtec.com>
Signed-off-by: NAleksandar Markovic <aleksandar.markovic@imgtec.com>
Reviewed-by: NJames Hogan <james.hogan@imgtec.com>
Cc: Douglas Leung <douglas.leung@imgtec.com>
Cc: Bo Hu <bohu@google.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/16887/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

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: NMiodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: NGoran Ferenc <goran.ferenc@imgtec.com>
Signed-off-by: NAleksandar Markovic <aleksandar.markovic@imgtec.com>
Reviewed-by: NJames 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: NRalf Baechle <ralf@linux-mips.org>

If accumulator value is zero, just return the value of previously
calculated product. This brings logic in MADDF/MSUBF implementation
closer to the logic in ADD/SUB case.
Signed-off-by: NMiodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: NGoran Ferenc <goran.ferenc@imgtec.com>
Signed-off-by: NAleksandar Markovic <aleksandar.markovic@imgtec.com>
Cc: James.Hogan@imgtec.com
Cc: Paul.Burton@imgtec.com
Cc: Raghu.Gandham@imgtec.com
Cc: Leonid.Yegoshin@imgtec.com
Cc: Douglas.Leung@imgtec.com
Cc: Petar.Jovanovic@imgtec.com
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16512/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

The code in _sp_maddf (formerly ieee754sp_madd) appears to have been
copied verbatim from ieee754sp_add, and although it's adding the
unpacked "r" & "z" floats it kept using macros that operate on "x" &
"y". This led to the addition being carried out incorrectly on some
mismash of the product, accumulator & multiplicand fields. Typically
this would lead to the assertions "ze == re" & "ze <= SP_EMAX" failing
since ze & re hadn't been operated upon.
Signed-off-by: NPaul Burton <paul.burton@imgtec.com>
Fixes: e24c3bec ("MIPS: math-emu: Add support for the MIPS R6 MADDF FPU instruction")
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Maciej W. Rozycki <macro@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13159/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

Introduce macros for handling the "z" argument to maddf & msubf, making
its handling consistent with that of the "x" & "y" arguments rather than
open-coding equivalents.
Signed-off-by: NPaul Burton <paul.burton@imgtec.com>
Cc: Maciej W. Rozycki <macro@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13156/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

The code for emulating MIPSr6 madd.s & msub.s instructions has
previously been implemented as 2 different functions, namely
ieee754sp_maddf & ieee754sp_msubf. The difference in behaviour of these
2 instructions is merely the sign of the product, so we can easily share
the code implementing them. Do this for the single precision variant,
removing the original ieee754sp_msubf in favor of reusing the code from
ieee754sp_maddf.
Signed-off-by: NPaul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13154/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

MIPS R6 introduced the following instruction:
Floating Point Fused Multiply Add:
MADDF.fmt To perform a fused multiply-add of FP values.

MADDF.fmt: FPR[fd] = FPR[fd] + (FPR[fs] x FPR[ft])
Signed-off-by: NMarkos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10956/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

Revert the changes made by commit fdffbafb [Lots of FPU bug fixes from
Kjeld Borch Egevang.] to `ieee754sp_nanxcpt' and `ieee754dp_nanxcpt'
sNaN quieting handlers and their callers so that sNaN processing is done
within the handlers againg.  Pass the sNaN causing an IEEE 754 invalid
operation exception down to the relevant handler.  Pass the sNaN in `fs'
where two sNaNs are supplied to a binary operation.

Set the Invalid Operation FCSR exception bits in the quieting handlers
rather than at their call sites throughout.  Make the handlers exclusive
for sNaN processing.
Signed-off-by: NMaciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9688/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

 o Only define variables in the outermost block
 o One empty line at most
 o Format comments as per CodingStyle
 o Update FSF address in licensing term comment
 o Spell FPU and MIPS in all capitals.
 o Remove ####-type of lines in comments.
 o Try to make things a bit most consistent between sp_*.c / dp_*.c files.
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

All it really did was throw a printk for no obvious reason.
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

Both were defined as 23 rsp. 52 though the mentissa is actually a bit more
than the fraction.
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

Having received another series of whitespace patches I decided to do this
once and for all rather than dealing with this kind of patches trickling
in forever.
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

Fixes generated by 'codespell' and manually reviewed.
Signed-off-by: NLucas De Marchi <lucas.demarchi@profusion.mobi>

The patch below updates broken web addresses in the arch directory.
Signed-off-by: NJustin P. Mattock <justinmattock@gmail.com>
Signed-off-by: NMaciej W. Rozycki <macro@linux-mips.org>
Cc: Finn Thain <fthain@telegraphics.com.au>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Reviewed-by: NFinn Thain <fthain@telegraphics.com.au>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!