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core/vm: reverse bit order in bytes of code bitmap (#24120)
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* 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
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@chfast
chfast committed Dec 17, 2021
1 parent bc6bf1e commit 81ec6b1
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Showing 2 changed files with 35 additions and 37 deletions.
32 changes: 13 additions & 19 deletions core/vm/analysis.go
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Expand Up @@ -17,53 +17,47 @@
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.
// An unset bit means the byte is an opcode, a set bit means
// 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
}

// 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.
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40 changes: 22 additions & 18 deletions core/vm/analysis_test.go
View file
Expand Up @@ -17,6 +17,7 @@
package vm

import (
"math/bits"
"testing"

"github.com/ethereum/go-ethereum/crypto"
Expand All @@ -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)
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