This is a reland of 6f93d59d.
One more test had to be disabled (tracked by bug 6954), and
two machops tests needed to be changed to use boxed floats
and doubles.

Original change's description:
> [test] Add nan bit patterns to uint{32,64}_vector
> 
> If you just cast those patterns to float or double and pass them
> around, the quiet/signaling NaN bit might change. We had several bugs
> around this, so add these patterns to the general input vectors.
> 
> This uncovers a bug in the wasm interpreter, which will be fixed in a
> separate CL.
> 
> R=ahaas@chromium.org
> 
> Bug: v8:6947, v8:6954
> Change-Id: I205b8ab784b087b1e4988190fa725df0b90e7ee0
> Reviewed-on: https://chromium-review.googlesource.com/725345
> Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
> Reviewed-by: Andreas Haas <ahaas@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#48731}

Bug: v8:6947, v8:6954
Change-Id: I9a38b5d9324131c3950c537910371a73c93d2c13
Reviewed-on: https://chromium-review.googlesource.com/728439Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48780}

This prepares fixes in the implementations of vabs and vneg (potentially
more). In order to implement them correctly, we need to preserve the
exact bit pattern.

R=ahaas@chromium.org, rodolph.perfetta@arm.com

Bug: v8:6947
Change-Id: I7194a60371a6e3c9ffba32981c90090ffafaa610
Reviewed-on: https://chromium-review.googlesource.com/722941Reviewed-by: Rodolph Perfetta <rodolph.perfetta@arm.com>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48648}

The class Float32 stores the bit pattern of a float as uint32_t to
guarantee that the exact bit pattern of the contained value is
preserved. This is necessary because the bit pattern of a NaN may
change, e.g. when it is passed as a parameter.

For convenience the Float32 class provides a constructor with a float
parameter. Since this constructor cannot guarantee that the right bit
pattern will be stored for NaNs, this CL adds a DCHECK now to make
sure that the constructor is never used with a NaN.

R=mstarzinger@chromium.org

Change-Id: Iba85a5a1bb2778d5f8bdc1aad97524ef8369b73d
Reviewed-on: https://chromium-review.googlesource.com/579367
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46811}

Apparently the name float.h causes problems on Windows when V8 is
compiled with Visual Studio, see the bug description.

R=clemensh@chromium.org

Bug: v8:6588
Change-Id: Iaa9c1e93e62509a779f1a8ddecbb03a53981cf8a
Reviewed-on: https://chromium-review.googlesource.com/578029Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46791}

This CL changes for floats what https://chromium-review.googlesource.com/c/558964/
changed for doubles.

Original message:
On x86, signalling NaNs get converted to quiet NaNs when they get push
on the stack and popped again. This happens in the code generation for
arm, specifically for the vmov instruction with the immediate parameter.
This CL replaces the vmov function in assembler-arm to take the
immediate as a uint64_t instead of a double, to guarantee that the bit
pattern does not change even if the parameter is a signalling NaN.

New in this CL:
Although src/double.h existed already, src/float.h did not exist yet.
I created the file in this CL, and moved the classes Float32 and
Float64 there, which already existed in src/deoptimizer.h.

R=titzer@chromium.org, martyn.capewell@arm.com, v8-arm-ports@googlegroups.com

BUG=v8:6564

Change-Id: I6a3f1f154af9c8cd4bb8e7e856235d3eee5e9edd
Reviewed-on: https://chromium-review.googlesource.com/561009
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Martyn Capewell <martyn.capewell@arm.com>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46473}