On float comparisons, we need a scratch byte register for the setcc
instruction, and if none is available, we spill. But this spilling code
is skipped if one of the operands is NaN. The cache state is updated
however, so following code assumes that the spill happened.
This CL fixes this by spilling before checking for NaN, such that the
spilling code is always executed.

R=titzer@chromium.org

Bug: v8:7582, v8:6600
Change-Id: I768d8de14e494d3ebea181c1f9f3129a4b005396
Reviewed-on: https://chromium-review.googlesource.com/973961Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52162}