tree c0669dbd33e791eae0d5748cb52edf07f80abc2f
parent 07f8992b1ccae2ea6042acbe5f66ac434bc018f0
author Cherry Zhang <cherryyz@google.com> 1546548989 -0500
committer Cherry Zhang <cherryyz@google.com> 1547136206 +0000

passes: remove write barriers for stack writes

Stack writes don't need write barriers. Also it is bad if a write
barrier is applied to a write on an uninitialized slot.

The frontend already tries not to insert write barriers for stack
writes, but as it is based on AST, it may not identify all the
stack writes. Here, with the SSA-based IR, we can identify the
remaining stack writes and elide the write barriers.

This is not ideal: it doesn't remove the conditional branch that
tests if the write barrier is enabled.

Change-Id: I8d4b299bc2ab9af49e4b4302ca1252edad5a685d
Reviewed-on: https://go-review.googlesource.com/c/157138
Reviewed-by: Than McIntosh <thanm@google.com>