cmd/gc: allocate non-escaping maps on stack
Extend escape analysis to make(map[k]v).
If it does not escape, allocate temp buffer for hmap and one bucket on stack.
There are 75 cases of non-escaping maps in std lib.
benchmark old allocs new allocs delta
BenchmarkConcurrentStmtQuery 16161 15161 -6.19%
BenchmarkConcurrentTxQuery 17658 16658 -5.66%
BenchmarkConcurrentTxStmtQuery 16157 15156 -6.20%
BenchmarkConcurrentRandom 13637 13114 -3.84%
BenchmarkManyConcurrentQueries 22 20 -9.09%
BenchmarkDecodeComplex128Slice 250 188 -24.80%
BenchmarkDecodeFloat64Slice 250 188 -24.80%
BenchmarkDecodeInt32Slice 250 188 -24.80%
BenchmarkDecodeStringSlice 2250 2188 -2.76%
BenchmarkNewEmptyMap 1 0 -100.00%
BenchmarkNewSmallMap 2 0 -100.00%
benchmark old ns/op new ns/op delta
BenchmarkNewEmptyMap 124 55.7 -55.08%
BenchmarkNewSmallMap 317 148 -53.31%
benchmark old allocs new allocs delta
BenchmarkNewEmptyMap 1 0 -100.00%
BenchmarkNewSmallMap 2 0 -100.00%
benchmark old bytes new bytes delta
BenchmarkNewEmptyMap 48 0 -100.00%
BenchmarkNewSmallMap 192 0 -100.00%
Fixes #5449
Change-Id: I24fa66f949d2f138885d9e66a0d160240dc9e8fa
Reviewed-on: https://go-review.googlesource.com/3508
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
diff --git a/test/escape2.go b/test/escape2.go
index 947dcc9..ca9f614 100644
--- a/test/escape2.go
+++ b/test/escape2.go
@@ -1751,3 +1751,20 @@
r := []rune{1, 2, 3} // ERROR "\[\]rune literal does not escape"
sink = string(r) // ERROR "string\(r\) escapes to heap"
}
+
+func makemap0() {
+ m := make(map[int]int) // ERROR "make\(map\[int\]int\, 0\) does not escape"
+ m[0] = 0
+ m[1]++
+ delete(m, 1)
+ sink = m[0]
+}
+
+func makemap1() map[int]int {
+ return make(map[int]int) // ERROR "make\(map\[int\]int\, 0\) escapes to heap"
+}
+
+func makemap2() {
+ m := make(map[int]int) // ERROR "make\(map\[int\]int\, 0\) escapes to heap"
+ sink = m
+}
