From 77f3e189d2bd4eb015235d200ca75803e45c87ef Mon Sep 17 00:00:00 2001
From: Rémy Oudompheng <oudomphe@phare.normalesup.org>
Date: Sun, 5 Aug 2012 21:35:41 +0200
Subject: runtime: faster string equality.

benchmark                                old ns/op    new ns/op    delta
BenchmarkCompareStringEqual                     51           35  -30.20%
BenchmarkCompareStringIdentical                 51            7  -85.71%
BenchmarkCompareStringSameLength                25           18  -28.29%
BenchmarkCompareStringDifferentLength            2            2   +1.46%

R=golang-dev, rsc
CC=golang-dev, remy
https://golang.org/cl/6450092
---
 src/pkg/runtime/alg.c          |  4 ++++
 src/pkg/runtime/string.goc     | 20 +++++++++++++++++++
 src/pkg/runtime/string_test.go | 45 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 69 insertions(+)
 create mode 100644 src/pkg/runtime/string_test.go

(limited to 'src/pkg/runtime')

diff --git a/src/pkg/runtime/alg.c b/src/pkg/runtime/alg.c
index bc848da38c..ce872755ff 100644
--- a/src/pkg/runtime/alg.c
+++ b/src/pkg/runtime/alg.c
@@ -324,6 +324,10 @@ runtime·strequal(bool *eq, uintptr s, void *a, void *b)
 		*eq = false;
 		return;
 	}
+	if(((String*)a)->str == ((String*)b)->str) {
+		*eq = true;
+		return;
+	}
 	runtime·memequal(eq, alen, ((String*)a)->str, ((String*)b)->str);
 }
 
diff --git a/src/pkg/runtime/string.goc b/src/pkg/runtime/string.goc
index 7cab6d2417..b72a1aa5e7 100644
--- a/src/pkg/runtime/string.goc
+++ b/src/pkg/runtime/string.goc
@@ -204,6 +204,26 @@ func cmpstring(s1 String, s2 String) (v int32) {
 	v = cmpstring(s1, s2);
 }
 
+func eqstring(s1 String, s2 String) (v bool) {
+	uint32 i, l;
+
+	if(s1.len != s2.len) {
+		v = false;
+		return;
+	}
+	if(s1.str == s2.str) {
+		v = true;
+		return;
+	}
+	l = s1.len;
+	for(i=0; i<l; i++)
+		if(s1.str[i] != s2.str[i]) {
+			v = false;
+			return;
+		}
+	v = true;
+}
+
 int32
 runtime·strcmp(byte *s1, byte *s2)
 {
diff --git a/src/pkg/runtime/string_test.go b/src/pkg/runtime/string_test.go
new file mode 100644
index 0000000000..8f13f0f428
--- /dev/null
+++ b/src/pkg/runtime/string_test.go
@@ -0,0 +1,45 @@
+package runtime_test
+
+import (
+	"testing"
+)
+
+func BenchmarkCompareStringEqual(b *testing.B) {
+	bytes := []byte("Hello Gophers!")
+	s1, s2 := string(bytes), string(bytes)
+	for i := 0; i < b.N; i++ {
+		if s1 != s2 {
+			b.Fatal("s1 != s2")
+		}
+	}
+}
+
+func BenchmarkCompareStringIdentical(b *testing.B) {
+	s1 := "Hello Gophers!"
+	s2 := s1
+	for i := 0; i < b.N; i++ {
+		if s1 != s2 {
+			b.Fatal("s1 != s2")
+		}
+	}
+}
+
+func BenchmarkCompareStringSameLength(b *testing.B) {
+	s1 := "Hello Gophers!"
+	s2 := "Hello, Gophers"
+	for i := 0; i < b.N; i++ {
+		if s1 == s2 {
+			b.Fatal("s1 == s2")
+		}
+	}
+}
+
+func BenchmarkCompareStringDifferentLength(b *testing.B) {
+	s1 := "Hello Gophers!"
+	s2 := "Hello, Gophers!"
+	for i := 0; i < b.N; i++ {
+		if s1 == s2 {
+			b.Fatal("s1 == s2")
+		}
+	}
+}
-- 
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