cmd/compile: establish regabi name/value mapping for small in-params

When the expand_calls phase in the SSA backend lowers prolog OpArg
values into OpArgIntReg/OpArgFloatReg values, we don't always record
the assocation between the new lowered value and the parameter name.

This patch handles the simple case where a given parameter fits into
exactly one register; in this scenario it makes sense to manufacture a
new pseudo-slot for the value that points to the param, and install
the slot/value mapping in the NamedValues table for the function. More
work will be needed to deal with params that span multiple registers;
that will need to be addressed in a subsequent patch.

This change improves the parameter error rate "optargorder" benchmark
by about 7-8% (when run on the optargorder binary).

Updates #45945.

Change-Id: Ic9adbe20b6f91145d49651348818f0f5cba92b18
Reviewed-on: https://go-review.googlesource.com/c/go/+/316890
Trust: Than McIntosh <thanm@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
1 file changed
tree: ee5428662b81326356f3320bbf74f1c5cea1d57e
  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. LICENSE
  14. PATENTS
  15. README.md
  16. SECURITY.md
  17. codereview.cfg
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