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| author | Dave Cheney <dave@cheney.net> | 2015-09-12 00:10:42 +1000 |
|---|---|---|
| committer | Dave Cheney <dave@cheney.net> | 2015-09-12 02:55:38 +0000 |
| commit | ea4e321d4daef32f4cd8df8ec799122ff3c6b9f0 (patch) | |
| tree | e224e2c91c0a61c9293ca6a00d8e8bbb3998542f | |
| parent | 3b0224282cf84228d6bcd4b783eb164e579fbd9e (diff) | |
| download | go-ea4e321d4daef32f4cd8df8ec799122ff3c6b9f0.tar.xz | |
cmd/compile/internal/gc: avoid allocation in bnum
Although bnum was being called with a Bits value, a limitation
of the escape analyser (golang/go#12588) meant that taking the
address of the Bits.b array in the range statement caused the
formal parameter to escape to the heap.
Passing the a pointer to a Bits, as with all the other Bits helper
methods avoids the allocation.
Before:
BenchmarkBnum1-4 20000000 69.6 ns/op 32 B/op 1 allocs/op
After:
BenchmarkBnum1-4 100000000 10.1 ns/op 0 B/op 0 allocs/op
Change-Id: I673bd57ddc032ee67d09474156d795fb1ba72018
Reviewed-on: https://go-review.googlesource.com/14501
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
| -rw-r--r-- | src/cmd/compile/internal/gc/reg.go | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/src/cmd/compile/internal/gc/reg.go b/src/cmd/compile/internal/gc/reg.go index b3e96216bd..ff6ec321a1 100644 --- a/src/cmd/compile/internal/gc/reg.go +++ b/src/cmd/compile/internal/gc/reg.go @@ -170,7 +170,7 @@ func setaddrs(bit Bits) { for bany(&bit) { // convert each bit to a variable - i = bnum(bit) + i = bnum(&bit) node = vars[i].node n = int(vars[i].name) @@ -1321,7 +1321,7 @@ loop2: bit.b[z] = LOAD(r, z) &^ (r.act.b[z] | addrs.b[z]) } for bany(&bit) { - i = bnum(bit) + i = bnum(&bit) change = 0 paint1(f, i) biclr(&bit, uint(i)) @@ -1465,7 +1465,7 @@ func bany(a *Bits) bool { } // bnum reports the lowest index of a 1 bit in a. -func bnum(a Bits) int { +func bnum(a *Bits) int { for i, x := range &a.b { // & to avoid making a copy of a.b if x != 0 { return 64*i + Bitno(x) @@ -1541,7 +1541,7 @@ func (bits Bits) String() string { var buf bytes.Buffer sep := "" for bany(&bits) { - i := bnum(bits) + i := bnum(&bits) buf.WriteString(sep) sep = " " v := &vars[i] |