core/vm: reverse bit order in bytes of code bitmap (#24120)

* core/vm: reverse bit order in bytes of code bitmap

This bit order is more natural for bit manipulation operations and we
can eliminate some small number of CPU instructions.

* core/vm: drop lookup table

core/vm/analysis.go

@@ -17,12 +17,12 @@
 package vm
 
 const (
-	set2BitsMask = uint16(0b1100_0000_0000_0000)
-	set3BitsMask = uint16(0b1110_0000_0000_0000)
-	set4BitsMask = uint16(0b1111_0000_0000_0000)
-	set5BitsMask = uint16(0b1111_1000_0000_0000)
-	set6BitsMask = uint16(0b1111_1100_0000_0000)
-	set7BitsMask = uint16(0b1111_1110_0000_0000)
+	set2BitsMask = uint16(0b11)
+	set3BitsMask = uint16(0b111)
+	set4BitsMask = uint16(0b1111)
+	set5BitsMask = uint16(0b1_1111)
+	set6BitsMask = uint16(0b11_1111)
+	set7BitsMask = uint16(0b111_1111)
 )
 
 // bitvec is a bit vector which maps bytes in a program.
@@ -30,32 +30,26 @@ const (
 // it's data (i.e. argument of PUSHxx).
 type bitvec []byte
 
-var lookup = [8]byte{
-	0x80, 0x40, 0x20, 0x10, 0x8, 0x4, 0x2, 0x1,
-}
-
 func (bits bitvec) set1(pos uint64) {
-	bits[pos/8] |= lookup[pos%8]
+	bits[pos/8] |= 1 << (pos % 8)
 }
 
 func (bits bitvec) setN(flag uint16, pos uint64) {
-	a := flag >> (pos % 8)
-	bits[pos/8] |= byte(a >> 8)
-	if b := byte(a); b != 0 {
-		//	If the bit-setting affects the neighbouring byte, we can assign - no need to OR it,
-		//	since it's the first write to that byte
+	a := flag << (pos % 8)
+	bits[pos/8] |= byte(a)
+	if b := byte(a >> 8); b != 0 {
 		bits[pos/8+1] = b
 	}
 }
 
 func (bits bitvec) set8(pos uint64) {
-	a := byte(0xFF >> (pos % 8))
+	a := byte(0xFF << (pos % 8))
 	bits[pos/8] |= a
 	bits[pos/8+1] = ^a
 }
 
 func (bits bitvec) set16(pos uint64) {
-	a := byte(0xFF >> (pos % 8))
+	a := byte(0xFF << (pos % 8))
 	bits[pos/8] |= a
 	bits[pos/8+1] = 0xFF
 	bits[pos/8+2] = ^a
@@ -63,7 +57,7 @@ func (bits bitvec) set16(pos uint64) {
 
 // codeSegment checks if the position is in a code segment.
 func (bits *bitvec) codeSegment(pos uint64) bool {
-	return ((*bits)[pos/8] & (0x80 >> (pos % 8))) == 0
+	return (((*bits)[pos/8] >> (pos % 8)) & 1) == 0
 }
 
 // codeBitmap collects data locations in code.

core/vm/analysis_test.go

@@ -17,6 +17,7 @@
 package vm
 
 import (
+	"math/bits"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/crypto"
@@ -28,24 +29,27 @@ func TestJumpDestAnalysis(t *testing.T) {
 		exp   byte
 		which int
 	}{
-		{[]byte{byte(PUSH1), 0x01, 0x01, 0x01}, 0x40, 0},
-		{[]byte{byte(PUSH1), byte(PUSH1), byte(PUSH1), byte(PUSH1)}, 0x50, 0},
-		{[]byte{byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), 0x01, 0x01, 0x01}, 0x7F, 0},
-		{[]byte{byte(PUSH8), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x80, 1},
-		{[]byte{0x01, 0x01, 0x01, 0x01, 0x01, byte(PUSH2), byte(PUSH2), byte(PUSH2), 0x01, 0x01, 0x01}, 0x03, 0},
-		{[]byte{0x01, 0x01, 0x01, 0x01, 0x01, byte(PUSH2), 0x01, 0x01, 0x01, 0x01, 0x01}, 0x00, 1},
-		{[]byte{byte(PUSH3), 0x01, 0x01, 0x01, byte(PUSH1), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x74, 0},
-		{[]byte{byte(PUSH3), 0x01, 0x01, 0x01, byte(PUSH1), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x00, 1},
-		{[]byte{0x01, byte(PUSH8), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x3F, 0},
-		{[]byte{0x01, byte(PUSH8), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0xC0, 1},
-		{[]byte{byte(PUSH16), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x7F, 0},
-		{[]byte{byte(PUSH16), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0xFF, 1},
-		{[]byte{byte(PUSH16), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x80, 2},
-		{[]byte{byte(PUSH8), 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, byte(PUSH1), 0x01}, 0x7f, 0},
-		{[]byte{byte(PUSH8), 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, byte(PUSH1), 0x01}, 0xA0, 1},
-		{[]byte{byte(PUSH32)}, 0x7F, 0},
-		{[]byte{byte(PUSH32)}, 0xFF, 1},
-		{[]byte{byte(PUSH32)}, 0xFF, 2},
+		{[]byte{byte(PUSH1), 0x01, 0x01, 0x01}, 0b0000_0010, 0},
+		{[]byte{byte(PUSH1), byte(PUSH1), byte(PUSH1), byte(PUSH1)}, 0b0000_1010, 0},
+		{[]byte{0x00, byte(PUSH1), 0x00, byte(PUSH1), 0x00, byte(PUSH1), 0x00, byte(PUSH1)}, 0b0101_0100, 0},
+		{[]byte{byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), 0x01, 0x01, 0x01}, bits.Reverse8(0x7F), 0},
+		{[]byte{byte(PUSH8), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b0000_0001, 1},
+		{[]byte{0x01, 0x01, 0x01, 0x01, 0x01, byte(PUSH2), byte(PUSH2), byte(PUSH2), 0x01, 0x01, 0x01}, 0b1100_0000, 0},
+		{[]byte{0x01, 0x01, 0x01, 0x01, 0x01, byte(PUSH2), 0x01, 0x01, 0x01, 0x01, 0x01}, 0b0000_0000, 1},
+		{[]byte{byte(PUSH3), 0x01, 0x01, 0x01, byte(PUSH1), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b0010_1110, 0},
+		{[]byte{byte(PUSH3), 0x01, 0x01, 0x01, byte(PUSH1), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b0000_0000, 1},
+		{[]byte{0x01, byte(PUSH8), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b1111_1100, 0},
+		{[]byte{0x01, byte(PUSH8), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b0000_0011, 1},
+		{[]byte{byte(PUSH16), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b1111_1110, 0},
+		{[]byte{byte(PUSH16), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b1111_1111, 1},
+		{[]byte{byte(PUSH16), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b0000_0001, 2},
+		{[]byte{byte(PUSH8), 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, byte(PUSH1), 0x01}, 0b1111_1110, 0},
+		{[]byte{byte(PUSH8), 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, byte(PUSH1), 0x01}, 0b0000_0101, 1},
+		{[]byte{byte(PUSH32)}, 0b1111_1110, 0},
+		{[]byte{byte(PUSH32)}, 0b1111_1111, 1},
+		{[]byte{byte(PUSH32)}, 0b1111_1111, 2},
+		{[]byte{byte(PUSH32)}, 0b1111_1111, 3},
+		{[]byte{byte(PUSH32)}, 0b0000_0001, 4},
 	}
 	for i, test := range tests {
 		ret := codeBitmap(test.code)