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| author | Josh Bleecher Snyder <josharian@gmail.com> | 2014-12-22 11:33:47 -0800 |
|---|---|---|
| committer | Josh Bleecher Snyder <josharian@gmail.com> | 2015-01-07 22:36:06 +0000 |
| commit | 43e6923131c4c83e02f5263a9632d81819f15a62 (patch) | |
| tree | 0300e13f1f583aaac87fef92c999c9e50d1908f5 /test/nilcheck.go | |
| parent | 43c87aa481f4e10777b05bf05edd15403853348f (diff) | |
| download | go-43e6923131c4c83e02f5263a9632d81819f15a62.tar.gz go-43e6923131c4c83e02f5263a9632d81819f15a62.zip | |
cmd/gc: optimize existence-only map lookups
The compiler converts 'val, ok = m[key]' to
tmp, ok = <runtime call>
val = *tmp
For lookups of the form '_, ok = m[key]',
the second statement is unnecessary.
By not generating it we save a nil check.
Change-Id: I21346cc195cb3c62e041af8b18770c0940358695
Reviewed-on: https://go-review.googlesource.com/1975
Reviewed-by: Russ Cox <rsc@golang.org>
Diffstat (limited to 'test/nilcheck.go')
| -rw-r--r-- | test/nilcheck.go | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/test/nilcheck.go b/test/nilcheck.go index fe05d05c92..99c3c5fdb6 100644 --- a/test/nilcheck.go +++ b/test/nilcheck.go @@ -182,3 +182,8 @@ func f4(x *[10]int) { _ = &x[9] // ERROR "nil check" } +func f5(m map[string]struct{}) bool { + // Existence-only map lookups should not generate a nil check + _, ok := m[""] + return ok +} |