cmd/compile: handle degenerate write barrier case

If both branches of a write barrier test go to the same block,
then there's no unsafe points.

This can only happen if the resulting memory state is somehow dead,
which can only occur in degenerate cases, like infinite loops. No
point in cleaning up the useless branch in these situations.

Fixes #26024.

Change-Id: I93a7df9fdf2fc94c6c4b1fe61180dc4fd4a0871f
Reviewed-on: https://go-review.googlesource.com/123655
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
2 files changed
tree: 5e1690662da0daf1a6dda3e4b7b9e43eddb92b3b
  1. .github/
  2. api/
  3. doc/
  4. lib/
  5. misc/
  6. src/
  7. test/
  8. .gitattributes
  9. .gitignore
  10. AUTHORS
  11. CONTRIBUTING.md
  12. CONTRIBUTORS
  13. favicon.ico
  14. LICENSE
  15. PATENTS
  16. README.md
  17. robots.txt
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