Shawn Nematbakhsh 90167c1764 math_util: Use HW instruction for int_sqrtf when available ...

Cortex-M4 supports a floating point square root function that takes 14
cycles to execute, which is a speed improvement over the existing binary
search, and saves flash space.

BUG=chromium:687624
BRANCH=None
TEST=On kevin, verify that both sqrtf methods (binary search vs HW
instruction) have identical results for fractional input (eg.
sqrt(15.999999) = 3), except when floating point representation of
square root rounds up to an integer. Verify identical results for all
integers [-100, 16793602). Note that 16793602 is the first integer for
which the floating point representation of sqrt rounds up to an integer.
Also verify basic motion sense functions on kevin.

Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Change-Id: I8521c9a28c958b340ca83c37342253e424df0c91
Reviewed-on: https://chromium-review.googlesource.com/537734
Commit-Ready: Shawn N <shawnn@chromium.org>
Tested-by: Shawn N <shawnn@chromium.org>
Reviewed-by: Shawn N <shawnn@chromium.org>

2017-06-19 15:33:09 -07:00

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