From 740992a5b4e647804b3d0fe83c920211dc0e6fd1 Mon Sep 17 00:00:00 2001
From: Alexey Ivanov <rbtz@ph34r.me>
Date: Wed, 6 Apr 2022 18:46:54 -0700
Subject: [PATCH] examples: simplify FNV1A loop

---
 examples/fnv1a/README.md | 6 +++---
 examples/fnv1a/asm.go    | 6 +++---
 examples/fnv1a/fnv1a.s   | 4 ++--
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/examples/fnv1a/README.md b/examples/fnv1a/README.md
index c9948a3b..cb0e1ee2 100644
--- a/examples/fnv1a/README.md
+++ b/examples/fnv1a/README.md
@@ -13,7 +13,8 @@ func main() {
 	TEXT("Hash64", NOSPLIT, "func(data []byte) uint64")
 	Doc("Hash64 computes the FNV-1a hash of data.")
 	ptr := Load(Param("data").Base(), GP64())
-	n := Load(Param("data").Len(), GP64())
+	endPtr := Load(Param("data").Len(), GP64())
+	ADDQ(ptr, endPtr)
 
 	h := RAX
 	MOVQ(Imm(OffsetBasis), h)
@@ -21,14 +22,13 @@ func main() {
 	MOVQ(Imm(Prime), p)
 
 	Label("loop")
-	CMPQ(n, Imm(0))
+	CMPQ(ptr, endPtr)
 	JE(LabelRef("done"))
 	b := GP64()
 	MOVBQZX(Mem{Base: ptr}, b)
 	XORQ(b, h)
 	MULQ(p)
 	INCQ(ptr)
-	DECQ(n)
 
 	JMP(LabelRef("loop"))
 	Label("done")
diff --git a/examples/fnv1a/asm.go b/examples/fnv1a/asm.go
index 809a1c95..474916a8 100644
--- a/examples/fnv1a/asm.go
+++ b/examples/fnv1a/asm.go
@@ -18,7 +18,8 @@ func main() {
 	TEXT("Hash64", NOSPLIT, "func(data []byte) uint64")
 	Doc("Hash64 computes the FNV-1a hash of data.")
 	ptr := Load(Param("data").Base(), GP64())
-	n := Load(Param("data").Len(), GP64())
+	endPtr := Load(Param("data").Len(), GP64())
+	ADDQ(ptr, endPtr)
 
 	h := RAX
 	MOVQ(Imm(OffsetBasis), h)
@@ -26,14 +27,13 @@ func main() {
 	MOVQ(Imm(Prime), p)
 
 	Label("loop")
-	CMPQ(n, Imm(0))
+	CMPQ(ptr, endPtr)
 	JE(LabelRef("done"))
 	b := GP64()
 	MOVBQZX(Mem{Base: ptr}, b)
 	XORQ(b, h)
 	MULQ(p)
 	INCQ(ptr)
-	DECQ(n)
 
 	JMP(LabelRef("loop"))
 	Label("done")
diff --git a/examples/fnv1a/fnv1a.s b/examples/fnv1a/fnv1a.s
index 6628c374..1fe0942c 100644
--- a/examples/fnv1a/fnv1a.s
+++ b/examples/fnv1a/fnv1a.s
@@ -6,17 +6,17 @@
 TEXT ·Hash64(SB), NOSPLIT, $0-32
 	MOVQ data_base+0(FP), CX
 	MOVQ data_len+8(FP), BX
+	ADDQ CX, BX
 	MOVQ $0xcbf29ce484222325, AX
 	MOVQ $0x00000100000001b3, SI
 
 loop:
-	CMPQ    BX, $0x00
+	CMPQ    CX, BX
 	JE      done
 	MOVBQZX (CX), DX
 	XORQ    DX, AX
 	MULQ    SI
 	INCQ    CX
-	DECQ    BX
 	JMP     loop
 
 done: