core/vm: optimize MSTORE and SLOAD (#16939)

* vm/test: add tests+benchmarks for mstore

* core/vm: less alloc and copying for mstore

* core/vm: less allocs in sload

* vm: check for errors more correctly

core/vm/memory.go

@@ -16,7 +16,12 @@
 
 package vm
 
-import "fmt"
+import (
+	"fmt"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common/math"
+)
 
 // Memory implements a simple memory model for the ethereum virtual machine.
 type Memory struct {
@@ -30,19 +35,32 @@ func NewMemory() *Memory {
 
 // Set sets offset + size to value
 func (m *Memory) Set(offset, size uint64, value []byte) {
-	// length of store may never be less than offset + size.
-	// The store should be resized PRIOR to setting the memory
-	if size > uint64(len(m.store)) {
-		panic("INVALID memory: store empty")
-	}
-
 	// It's possible the offset is greater than 0 and size equals 0. This is because
 	// the calcMemSize (common.go) could potentially return 0 when size is zero (NO-OP)
 	if size > 0 {
+		// length of store may never be less than offset + size.
+		// The store should be resized PRIOR to setting the memory
+		if offset+size > uint64(len(m.store)) {
+			panic("invalid memory: store empty")
+		}
 		copy(m.store[offset:offset+size], value)
 	}
 }
 
+// Set32 sets the 32 bytes starting at offset to the value of val, left-padded with zeroes to
+// 32 bytes.
+func (m *Memory) Set32(offset uint64, val *big.Int) {
+	// length of store may never be less than offset + size.
+	// The store should be resized PRIOR to setting the memory
+	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
+	math.ReadBits(val, m.store[offset:offset+32])
+}
+
 // Resize resizes the memory to size
 func (m *Memory) Resize(size uint64) {
 	if uint64(m.Len()) < size {