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compiler: emit short jumps where possible

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Convert long jumps to short ones if the offset
can be represented in a single byte.

Close #805.
This commit is contained in:
Evgenii Stratonikov 2020-08-19 12:36:17 +03:00
parent 681e81420a
commit cfa62e7051
2 changed files with 246 additions and 8 deletions
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119
pkg/compiler/jumps_test.go Normal file
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@ -0,0 +1,119 @@
package compiler
import (
"testing"
"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
"github.com/stretchr/testify/require"
)
func testShortenJumps(t *testing.T, before, after []opcode.Opcode, indices []int) {
prog := make([]byte, len(before))
for i := range before {
prog[i] = byte(before[i])
}
raw := shortenJumps(prog, indices)
actual := make([]opcode.Opcode, len(raw))
for i := range raw {
actual[i] = opcode.Opcode(raw[i])
}
require.Equal(t, after, actual)
}
func TestShortenJumps(t *testing.T) {
testCases := map[opcode.Opcode]opcode.Opcode{
opcode.JMPL: opcode.JMP,
opcode.JMPIFL: opcode.JMPIF,
opcode.JMPIFNOTL: opcode.JMPIFNOT,
opcode.JMPEQL: opcode.JMPEQ,
opcode.JMPNEL: opcode.JMPNE,
opcode.JMPGTL: opcode.JMPGT,
opcode.JMPGEL: opcode.JMPGE,
opcode.JMPLEL: opcode.JMPLE,
opcode.JMPLTL: opcode.JMPLT,
opcode.CALLL: opcode.CALL,
}
for op, sop := range testCases {
t.Run(op.String(), func(t *testing.T) {
before := []opcode.Opcode{
op, 6, 0, 0, 0, opcode.PUSH1, opcode.NOP, // <- first jump to here
op, 9, 12, 0, 0, opcode.PUSH1, opcode.NOP, // <- last jump to here
op, 255, 0, 0, 0, op, 0xFF - 5, 0xFF, 0xFF, 0xFF,
}
after := []opcode.Opcode{
sop, 3, opcode.PUSH1, opcode.NOP,
op, 3, 12, 0, 0, opcode.PUSH1, opcode.NOP,
sop, 249, sop, 0xFF - 2,
}
testShortenJumps(t, before, after, []int{0, 14, 19})
})
}
t.Run("NoReplace", func(t *testing.T) {
b := []byte{0, 1, 2, 3, 4, 5}
expected := []byte{0, 1, 2, 3, 4, 5}
require.Equal(t, expected, shortenJumps(b, nil))
})
t.Run("InvalidIndex", func(t *testing.T) {
before := []byte{byte(opcode.PUSH1), 0, 0, 0, 0}
require.Panics(t, func() {
shortenJumps(before, []int{0})
})
})
t.Run("SideConditions", func(t *testing.T) {
t.Run("Forward", func(t *testing.T) {
before := []opcode.Opcode{
opcode.JMPL, 5, 0, 0, 0,
opcode.JMPL, 5, 0, 0, 0,
}
after := []opcode.Opcode{
opcode.JMP, 2,
opcode.JMP, 2,
}
testShortenJumps(t, before, after, []int{0, 5})
})
t.Run("Backwards", func(t *testing.T) {
before := []opcode.Opcode{
opcode.JMPL, 5, 0, 0, 0,
opcode.JMPL, 0xFF - 4, 0xFF, 0xFF, 0xFF,
opcode.JMPL, 0xFF - 4, 0xFF, 0xFF, 0xFF,
}
after := []opcode.Opcode{
opcode.JMPL, 5, 0, 0, 0,
opcode.JMP, 0xFF - 4,
opcode.JMP, 0xFF - 1,
}
testShortenJumps(t, before, after, []int{5, 10})
})
})
}
func TestWriteJumps(t *testing.T) {
c := new(codegen)
c.l = []int{10}
before := []byte{
byte(opcode.NOP), byte(opcode.JMP), 2, byte(opcode.RET),
byte(opcode.CALLL), 0, 0, 0, 0, byte(opcode.RET),
byte(opcode.PUSH2), byte(opcode.RET),
}
c.funcs = map[string]*funcScope{
"init": {rng: DebugRange{Start: 0, End: 3}},
"main": {rng: DebugRange{Start: 4, End: 9}},
"method": {rng: DebugRange{Start: 10, End: 11}},
}
expProg := []byte{
byte(opcode.NOP), byte(opcode.JMP), 2, byte(opcode.RET),
byte(opcode.CALL), 3, byte(opcode.RET),
byte(opcode.PUSH2), byte(opcode.RET),
}
expFuncs := map[string]*funcScope{
"init": {rng: DebugRange{Start: 0, End: 3}},
"main": {rng: DebugRange{Start: 4, End: 6}},
"method": {rng: DebugRange{Start: 7, End: 8}},
}
buf, err := c.writeJumps(before)
require.NoError(t, err)
require.Equal(t, expProg, buf)
require.Equal(t, expFuncs, c.funcs)
}