core/vm: optimize Memory.Set32 (ethereum#24847)

qianbin · jagdeep sidhu · commit 7d9ed98019cb · 2022-05-31T09:33:57.000-07:00
* core/vm: remove unnecessary memset for Memory.Set32

* core/vm: optimize Memory.Set32
diff --git a/core/vm/memory.go b/core/vm/memory.go
@@ -53,10 +53,9 @@ func (m *Memory) Set32(offset uint64, val *uint256.Int) {
 	if offset+32 > uint64(len(m.store)) {
 		panic("invalid memory: store empty")
 	}
-	// Zero the memory area
-	copy(m.store[offset:offset+32], []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0})
 	// Fill in relevant bits
-	val.WriteToSlice(m.store[offset:])
+	b32 := val.Bytes32()
+	copy(m.store[offset:], b32[:])
 }
 
 // Resize resizes the memory to size

Original file line number	Diff line number	Diff line change
`@@ -53,10 +53,9 @@ func (m Memory) Set32(offset uint64, val uint256.Int) {`
`53`	`53`	`if offset+32 > uint64(len(m.store)) {`
`54`	`54`	`panic("invalid memory: store empty")`
`55`	`55`	`}`
`56`		`- // Zero the memory area`
`57`		`- copy(m.store[offset:offset+32], []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0})`
`58`	`56`	`// Fill in relevant bits`
`59`		`- val.WriteToSlice(m.store[offset:])`
	`57`	`+ b32 := val.Bytes32()`
	`58`	`+ copy(m.store[offset:], b32[:])`
`60`	`59`	`}`
`61`	`60`
`62`	`61`	`// Resize resizes the memory to size`