Skip to content

Commit 81ec6b1

Browse files
chfastchfast
authored
core/vm: reverse bit order in bytes of code bitmap (ethereum#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
1 parent bc6bf1e commit 81ec6b1

File tree

2 files changed

+35
-37
lines changed

2 files changed

+35
-37
lines changed

‎core/vm/analysis.go‎

Lines changed: 13 additions & 19 deletions
Original file line numberDiff line numberDiff line change
@@ -17,53 +17,47 @@
1717
package vm
1818

1919
const (
20-
set2BitsMask = uint16(0b1100_0000_0000_0000)
21-
set3BitsMask = uint16(0b1110_0000_0000_0000)
22-
set4BitsMask = uint16(0b1111_0000_0000_0000)
23-
set5BitsMask = uint16(0b1111_1000_0000_0000)
24-
set6BitsMask = uint16(0b1111_1100_0000_0000)
25-
set7BitsMask = uint16(0b1111_1110_0000_0000)
20+
set2BitsMask = uint16(0b11)
21+
set3BitsMask = uint16(0b111)
22+
set4BitsMask = uint16(0b1111)
23+
set5BitsMask = uint16(0b1_1111)
24+
set6BitsMask = uint16(0b11_1111)
25+
set7BitsMask = uint16(0b111_1111)
2626
)
2727

2828
// bitvec is a bit vector which maps bytes in a program.
2929
// An unset bit means the byte is an opcode, a set bit means
3030
// it's data (i.e. argument of PUSHxx).
3131
type bitvec []byte
3232

33-
var lookup = [8]byte{
34-
0x80, 0x40, 0x20, 0x10, 0x8, 0x4, 0x2, 0x1,
35-
}
36-
3733
func (bits bitvec) set1(pos uint64) {
38-
bits[pos/8] |= lookup[pos%8]
34+
bits[pos/8] |= 1 << (pos % 8)
3935
}
4036

4137
func (bits bitvec) setN(flag uint16, pos uint64) {
42-
a := flag >> (pos % 8)
43-
bits[pos/8] |= byte(a >> 8)
44-
if b := byte(a); b != 0 {
45-
// If the bit-setting affects the neighbouring byte, we can assign - no need to OR it,
46-
// since it's the first write to that byte
38+
a := flag << (pos % 8)
39+
bits[pos/8] |= byte(a)
40+
if b := byte(a >> 8); b != 0 {
4741
bits[pos/8+1] = b
4842
}
4943
}
5044

5145
func (bits bitvec) set8(pos uint64) {
52-
a := byte(0xFF >> (pos % 8))
46+
a := byte(0xFF << (pos % 8))
5347
bits[pos/8] |= a
5448
bits[pos/8+1] = ^a
5549
}
5650

5751
func (bits bitvec) set16(pos uint64) {
58-
a := byte(0xFF >> (pos % 8))
52+
a := byte(0xFF << (pos % 8))
5953
bits[pos/8] |= a
6054
bits[pos/8+1] = 0xFF
6155
bits[pos/8+2] = ^a
6256
}
6357

6458
// codeSegment checks if the position is in a code segment.
6559
func (bits *bitvec) codeSegment(pos uint64) bool {
66-
return ((*bits)[pos/8] & (0x80 >> (pos % 8))) == 0
60+
return (((*bits)[pos/8] >> (pos % 8)) & 1) == 0
6761
}
6862

6963
// codeBitmap collects data locations in code.

‎core/vm/analysis_test.go‎

Lines changed: 22 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -17,6 +17,7 @@
1717
package vm
1818

1919
import (
20+
"math/bits"
2021
"testing"
2122

2223
"github.com/ethereum/go-ethereum/crypto"
@@ -28,24 +29,27 @@ func TestJumpDestAnalysis(t *testing.T) {
2829
exp byte
2930
which int
3031
}{
31-
{[]byte{byte(PUSH1), 0x01, 0x01, 0x01}, 0x40, 0},
32-
{[]byte{byte(PUSH1), byte(PUSH1), byte(PUSH1), byte(PUSH1)}, 0x50, 0},
33-
{[]byte{byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), 0x01, 0x01, 0x01}, 0x7F, 0},
34-
{[]byte{byte(PUSH8), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x80, 1},
35-
{[]byte{0x01, 0x01, 0x01, 0x01, 0x01, byte(PUSH2), byte(PUSH2), byte(PUSH2), 0x01, 0x01, 0x01}, 0x03, 0},
36-
{[]byte{0x01, 0x01, 0x01, 0x01, 0x01, byte(PUSH2), 0x01, 0x01, 0x01, 0x01, 0x01}, 0x00, 1},
37-
{[]byte{byte(PUSH3), 0x01, 0x01, 0x01, byte(PUSH1), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x74, 0},
38-
{[]byte{byte(PUSH3), 0x01, 0x01, 0x01, byte(PUSH1), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x00, 1},
39-
{[]byte{0x01, byte(PUSH8), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x3F, 0},
40-
{[]byte{0x01, byte(PUSH8), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0xC0, 1},
41-
{[]byte{byte(PUSH16), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x7F, 0},
42-
{[]byte{byte(PUSH16), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0xFF, 1},
43-
{[]byte{byte(PUSH16), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0x80, 2},
44-
{[]byte{byte(PUSH8), 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, byte(PUSH1), 0x01}, 0x7f, 0},
45-
{[]byte{byte(PUSH8), 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, byte(PUSH1), 0x01}, 0xA0, 1},
46-
{[]byte{byte(PUSH32)}, 0x7F, 0},
47-
{[]byte{byte(PUSH32)}, 0xFF, 1},
48-
{[]byte{byte(PUSH32)}, 0xFF, 2},
32+
{[]byte{byte(PUSH1), 0x01, 0x01, 0x01}, 0b0000_0010, 0},
33+
{[]byte{byte(PUSH1), byte(PUSH1), byte(PUSH1), byte(PUSH1)}, 0b0000_1010, 0},
34+
{[]byte{0x00, byte(PUSH1), 0x00, byte(PUSH1), 0x00, byte(PUSH1), 0x00, byte(PUSH1)}, 0b0101_0100, 0},
35+
{[]byte{byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), byte(PUSH8), 0x01, 0x01, 0x01}, bits.Reverse8(0x7F), 0},
36+
{[]byte{byte(PUSH8), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b0000_0001, 1},
37+
{[]byte{0x01, 0x01, 0x01, 0x01, 0x01, byte(PUSH2), byte(PUSH2), byte(PUSH2), 0x01, 0x01, 0x01}, 0b1100_0000, 0},
38+
{[]byte{0x01, 0x01, 0x01, 0x01, 0x01, byte(PUSH2), 0x01, 0x01, 0x01, 0x01, 0x01}, 0b0000_0000, 1},
39+
{[]byte{byte(PUSH3), 0x01, 0x01, 0x01, byte(PUSH1), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b0010_1110, 0},
40+
{[]byte{byte(PUSH3), 0x01, 0x01, 0x01, byte(PUSH1), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b0000_0000, 1},
41+
{[]byte{0x01, byte(PUSH8), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b1111_1100, 0},
42+
{[]byte{0x01, byte(PUSH8), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b0000_0011, 1},
43+
{[]byte{byte(PUSH16), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b1111_1110, 0},
44+
{[]byte{byte(PUSH16), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b1111_1111, 1},
45+
{[]byte{byte(PUSH16), 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01}, 0b0000_0001, 2},
46+
{[]byte{byte(PUSH8), 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, byte(PUSH1), 0x01}, 0b1111_1110, 0},
47+
{[]byte{byte(PUSH8), 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, byte(PUSH1), 0x01}, 0b0000_0101, 1},
48+
{[]byte{byte(PUSH32)}, 0b1111_1110, 0},
49+
{[]byte{byte(PUSH32)}, 0b1111_1111, 1},
50+
{[]byte{byte(PUSH32)}, 0b1111_1111, 2},
51+
{[]byte{byte(PUSH32)}, 0b1111_1111, 3},
52+
{[]byte{byte(PUSH32)}, 0b0000_0001, 4},
4953
}
5054
for i, test := range tests {
5155
ret := codeBitmap(test.code)

0 commit comments

Comments
 (0)