add fnv1a example

examples/fnv1a/asm.go

@@ -0,0 +1,41 @@
+// +build ignore
+
+package main
+
+import (
+	. "github.com/mmcloughlin/avo/build"
+	"github.com/mmcloughlin/avo/operand"
+	"github.com/mmcloughlin/avo/reg"
+)
+
+const (
+	OffsetBasis = 0xcbf29ce484222325
+	Prime       = 0x100000001b3
+)
+
+func main() {
+	TEXT("Hash64", "func(data []byte) uint64")
+	ptr := Load(Param("data").Base(), GP64v())
+	n := Load(Param("data").Len(), GP64v())
+
+	h := reg.RAX
+	MOVQ(operand.Imm(OffsetBasis), h)
+	p := GP64v()
+	MOVQ(operand.Imm(Prime), p)
+
+	LABEL("loop")
+	CMPQ(n, operand.Imm(0))
+	JE(operand.LabelRef("done"))
+	b := GP64v()
+	MOVBQZX(operand.Mem{Base: ptr}, b)
+	XORQ(b, h)
+	MULQ(p)
+	INCQ(ptr)
+	DECQ(n)
+
+	JMP(operand.LabelRef("loop"))
+	LABEL("done")
+	Store(h, ReturnIndex(0))
+	RET()
+	Generate()
+}