commit | b800f202dc4d4281edd56ec40ea58f09dac8b730 | [log] [tgz] |
---|---|---|
author | Austin Clements <austin@google.com> | Fri Aug 03 11:34:11 2018 -0400 |
committer | Austin Clements <austin@google.com> | Fri Aug 03 18:35:45 2018 +0000 |
tree | aed762c1263d74dad4293c6a5619264deb24be04 | |
parent | 1b870077c896379c066b41657d3c9062097a6943 [diff] |
runtime: document assumption about wbBufFlush argument slots gcWriteBarrier and wbBufFlush assume that not writing to an argument variable is sufficient to not clobber the corresponding argument slot. This assumption lets us simplify the write barrier assembly code, speed up the flush path, and reduce the stack usage of the write barrier. But it is an assumption, so this CL documents it to make this clear. Alternatively, we could separate the register spill slots from the argument slots in the write barrier, but that loses the advantages above. On the other hand, it's extremely unlikely that we'll change the behavior of the compiler to start clobbering argument slots (if anything, we'd probably change it to *not* clobber argument slots even if you wrote to the arguments). Fixes #25512. Change-Id: Ib2cf29c0d90956ca02b997ef6e7fa56fc8044efe Reviewed-on: https://go-review.googlesource.com/127815 Reviewed-by: Cherry Zhang <cherryyz@google.com>
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