cmd/compile: optimize single-precision floating point square root

Add generic rule to rewrite the single-precision square root expression
with one single-precision instruction. The optimization will reduce two
times of precision converting between double-precision and single-precision.

On arm64 flatform.

previous:
  FCVTSD F0, F0
  FSQRTD F0, F0
  FCVTDS F0, F0

optimized:
  FSQRTS S0, S0

And this patch adds the test case to check the correctness.

This patch refers to CL 241877, contributed by Alice Xu
(dianhong.xu@arm.com)

Change-Id: I6de5d02281c693017ac4bd4c10963dd55989bd7e
Reviewed-on: https://go-review.googlesource.com/c/go/+/276873
Trust: fannie zhang <Fannie.Zhang@arm.com>
Run-TryBot: fannie zhang <Fannie.Zhang@arm.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
41 files changed
tree: 86c8adabbab0b962827eebb995e054fc5ac6098d
  1. .gitattributes
  2. .github/
  3. .gitignore
  4. AUTHORS
  5. CONTRIBUTING.md
  6. CONTRIBUTORS
  7. LICENSE
  8. PATENTS
  9. README.md
  10. SECURITY.md
  11. api/
  12. codereview.cfg
  13. doc/
  14. favicon.ico
  15. lib/
  16. misc/
  17. robots.txt
  18. src/
  19. test/
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