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Keith Randall 256a605faa cmd/compile: don't use nilcheck information until the next block
When nilcheck runs, the values in a block are not in any particular
order.  So any facts derived from examining the blocks shouldn't be
used until we reach the next block.

This is suboptimal as it won't eliminate nil checks within a block.
But it's probably a better fix for now as it is a much smaller change
than other strategies for fixing this bug.

nilptr3.go changes are mostly because for this pattern:
  _ = *p
  _ = *p
either nil check is fine to keep, and this CL changes which one
the compiler tends to keep.
There are a few regressions from code like this:
  _ = *p
  f()
  _ = *p
For this pattern, after this CL we issue 2 nil checks instead of one.
(For the curious, this happens because intra-block nil check
 elimination now falls to CSE, not nilcheck proper.  The former
 pattern has two nil checks with the same store argument.  The latter
 pattern has two nil checks with different store arguments.)

Fixes #18725

Change-Id: I3721b494c8bc9ba1142dc5c4361ea55c66920ac8
Reviewed-on: https://go-review.googlesource.com/35485
Reviewed-by: Cherry Zhang <cherryyz@google.com>
2017-01-20 20:21:55 +00:00
.github doc: improve issue template 2016-08-29 03:33:28 +00:00
api Revert "cmd/go: note when some Go files were ignored on no-Go-files errors" 2016-12-21 05:25:57 +00:00
doc crypto/x509: revert SystemCertPool implementation for Windows 2017-01-18 05:41:15 +00:00
lib/time lib/time: update tzdata to 2016j 2017-01-05 01:00:53 +00:00
misc runtime: check for nil g and m in msanread 2017-01-19 23:06:54 +00:00
src cmd/compile: don't use nilcheck information until the next block 2017-01-20 20:21:55 +00:00
test cmd/compile: don't use nilcheck information until the next block 2017-01-20 20:21:55 +00:00
.gitattributes
.gitignore .gitignore: fix attempt at rooted paths 2017-01-05 01:29:25 +00:00
AUTHORS A+C: automated update 2016-12-21 03:22:22 +00:00
CONTRIBUTING.md doc: update CONTRIBUTING.md a bit, mention proposal process 2017-01-06 23:19:01 +00:00
CONTRIBUTORS A+C: automated update 2016-12-21 03:22:22 +00:00
LICENSE doc: revert copyright date to 2009 2016-06-01 22:40:04 +00:00
PATENTS
README.md README.md: update and simplify 2017-01-17 21:26:43 +00:00
favicon.ico website: recreate 16px and 32px favicon 2016-08-25 15:43:32 +00:00
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README.md

The Go Programming Language

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