src/runtime: switch to stronger hash function

Fixes #2713

src/runtime/memhash_tsip.go

@@ -0,0 +1,161 @@
+//go:build runtime_memhash_tsip
+// +build runtime_memhash_tsip
+
+package runtime
+
+import (
+	"encoding/binary"
+	"math/bits"
+	"unsafe"
+)
+
+func ptrToSlice(ptr unsafe.Pointer, n uintptr) []byte {
+	var p []byte
+
+	type _bslice struct {
+		ptr *byte
+		len uintptr
+		cap uintptr
+	}
+
+	pslice := (*_bslice)(unsafe.Pointer(&p))
+	pslice.ptr = (*byte)(ptr)
+	pslice.cap = n
+	pslice.len = n
+
+	return p
+}
+
+// tsip hash -- github.com/dgryski/tsip
+
+type sip struct {
+	v0, v1 uint64
+}
+
+func (s *sip) round() {
+	s.v0 += s.v1
+	s.v1 = bits.RotateLeft64(s.v1, 13) ^ s.v0
+	s.v0 = bits.RotateLeft64(s.v0, 35) + s.v1
+	s.v1 = bits.RotateLeft64(s.v1, 17) ^ s.v0
+	s.v0 = bits.RotateLeft64(s.v0, 21)
+}
+
+func hash64(ptr unsafe.Pointer, n uintptr, seed uintptr) uint64 {
+
+	p := ptrToSlice(ptr, n)
+
+	k0 := uint64(seed)
+	k1 := uint64(0)
+
+	s := sip{
+		v0: k0 ^ 0x736f6d6570736575,
+		v1: k1 ^ 0x646f72616e646f6d,
+	}
+
+	b := uint64(len(p)) << 56
+
+	for len(p) >= 8 {
+		m := binary.LittleEndian.Uint64(p[:8])
+		s.v1 ^= m
+		s.round()
+		s.v0 ^= m
+		p = p[8:]
+	}
+
+	switch len(p) {
+	case 7:
+		b |= uint64(p[6]) << 48
+		fallthrough
+	case 6:
+		b |= uint64(p[5]) << 40
+		fallthrough
+	case 5:
+		b |= uint64(p[4]) << 32
+		fallthrough
+	case 4:
+		b |= uint64(p[3]) << 24
+		fallthrough
+	case 3:
+		b |= uint64(p[2]) << 16
+		fallthrough
+	case 2:
+		b |= uint64(p[1]) << 8
+		fallthrough
+	case 1:
+		b |= uint64(p[0])
+	}
+
+	// last block
+	s.v1 ^= b
+	s.round()
+	s.v0 ^= b
+
+	// finalization
+	s.v1 ^= 0xff
+	s.round()
+	s.v1 = bits.RotateLeft64(s.v1, 32)
+	s.round()
+	s.v1 = bits.RotateLeft64(s.v1, 32)
+
+	return s.v0 ^ s.v1
+}
+
+type sip32 struct {
+	v0, v1 uint32
+}
+
+func (s *sip32) round() {
+	s.v0 += s.v1
+	s.v1 = bits.RotateLeft32(s.v1, 5) ^ s.v0
+	s.v0 = bits.RotateLeft32(s.v0, 8) + s.v1
+	s.v1 = bits.RotateLeft32(s.v1, 13) ^ s.v0
+	s.v0 = bits.RotateLeft32(s.v0, 7)
+}
+
+func hash32(ptr unsafe.Pointer, n uintptr, seed uintptr) uint32 {
+	// TODO(dgryski): replace this messiness with unsafe.Slice when we can use 1.17 features
+
+	p := ptrToSlice(ptr, n)
+
+	k0 := uint32(seed)
+	k1 := uint32(seed >> 32)
+
+	s := sip32{
+		v0: k0 ^ 0x74656462,
+		v1: k1 ^ 0x6c796765,
+	}
+	b := uint32(len(p)) << 24
+
+	for len(p) >= 4 {
+		m := binary.LittleEndian.Uint32(p[:4])
+		s.v1 ^= m
+		s.round()
+		s.v0 ^= m
+		p = p[4:]
+	}
+
+	switch len(p) {
+	case 3:
+		b |= uint32(p[2]) << 16
+		fallthrough
+	case 2:
+		b |= uint32(p[1]) << 8
+		fallthrough
+	case 1:
+		b |= uint32(p[0])
+	}
+
+	// last block
+	s.v1 ^= b
+	s.round()
+	s.v0 ^= b
+
+	// finalization
+	s.v1 ^= 0xff
+	s.round()
+	s.v1 = bits.RotateLeft32(s.v1, 16)
+	s.round()
+	s.v1 = bits.RotateLeft32(s.v1, 16)
+
+	return s.v0 ^ s.v1
+}