1 files changed, 120 insertions, 0 deletions
diff --git a/libgo/go/bytes/bytes_s390x.go b/libgo/go/bytes/bytes_s390x.go
new file mode 100644
index 00000000000..a05ca47aa16
--- /dev/null
+++ b/libgo/go/bytes/bytes_s390x.go
@@ -0,0 +1,120 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build ignore
+
+package bytes
+
+//go:noescape
+
+// indexShortStr returns the index of the first instance of sep in s,
+// or -1 if sep is not present in s.
+// indexShortStr requires 2 <= len(sep) <= shortStringLen
+func indexShortStr(s, c []byte) int // ../runtime/asm_s390x.s
+
+// supportsVX reports whether the vector facility is available.
+// indexShortStr must not be called if the vector facility is not
+// available.
+func supportsVX() bool // ../runtime/asm_s390x.s
+
+var shortStringLen = -1
+
+func init() {
+	if supportsVX() {
+		shortStringLen = 64
+	}
+}
+
+// Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
+func Index(s, sep []byte) int {
+	n := len(sep)
+	switch {
+	case n == 0:
+		return 0
+	case n == 1:
+		return IndexByte(s, sep[0])
+	case n == len(s):
+		if Equal(sep, s) {
+			return 0
+		}
+		return -1
+	case n > len(s):
+		return -1
+	case n <= shortStringLen:
+		// Use brute force when s and sep both are small
+		if len(s) <= 64 {
+			return indexShortStr(s, sep)
+		}
+		c := sep[0]
+		i := 0
+		t := s[:len(s)-n+1]
+		fails := 0
+		for i < len(t) {
+			if t[i] != c {
+				// IndexByte skips 16/32 bytes per iteration,
+				// so it's faster than indexShortStr.
+				o := IndexByte(t[i:], c)
+				if o < 0 {
+					return -1
+				}
+				i += o
+			}
+			if Equal(s[i:i+n], sep) {
+				return i
+			}
+			fails++
+			i++
+			// Switch to indexShortStr when IndexByte produces too many false positives.
+			// Too many means more that 1 error per 8 characters.
+			// Allow some errors in the beginning.
+			if fails > (i+16)/8 {
+				r := indexShortStr(s[i:], sep)
+				if r >= 0 {
+					return r + i
+				}
+				return -1
+			}
+		}
+		return -1
+	}
+	// Rabin-Karp search
+	hashsep, pow := hashStr(sep)
+	var h uint32
+	for i := 0; i < n; i++ {
+		h = h*primeRK + uint32(s[i])
+	}
+	if h == hashsep && Equal(s[:n], sep) {
+		return 0
+	}
+	for i := n; i < len(s); {
+		h *= primeRK
+		h += uint32(s[i])
+		h -= pow * uint32(s[i-n])
+		i++
+		if h == hashsep && Equal(s[i-n:i], sep) {
+			return i - n
+		}
+	}
+	return -1
+}
+
+// primeRK is the prime base used in Rabin-Karp algorithm.
+const primeRK = 16777619
+
+// hashStr returns the hash and the appropriate multiplicative
+// factor for use in Rabin-Karp algorithm.
+func hashStr(sep []byte) (uint32, uint32) {
+	hash := uint32(0)
+	for i := 0; i < len(sep); i++ {
+		hash = hash*primeRK + uint32(sep[i])
+	}
+	var pow, sq uint32 = 1, primeRK
+	for i := len(sep); i > 0; i >>= 1 {
+		if i&1 != 0 {
+			pow *= sq
+		}
+		sq *= sq
+	}
+	return hash, pow
+}