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/**
* Copyright 2023 ByteDance Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package loader
import (
`encoding/binary`
)
const (
_N_PCDATA = 4
_PCDATA_UnsafePoint = 0
_PCDATA_StackMapIndex = 1
_PCDATA_InlTreeIndex = 2
_PCDATA_ArgLiveIndex = 3
_PCDATA_INVALID_OFFSET = 0
)
const (
// PCDATA_UnsafePoint values.
PCDATA_UnsafePointSafe = -1 // Safe for async preemption
PCDATA_UnsafePointUnsafe = -2 // Unsafe for async preemption
// PCDATA_Restart1(2) apply on a sequence of instructions, within
// which if an async preemption happens, we should back off the PC
// to the start of the sequence when resume.
// We need two so we can distinguish the start/end of the sequence
// in case that two sequences are next to each other.
PCDATA_Restart1 = -3
PCDATA_Restart2 = -4
// Like PCDATA_RestartAtEntry, but back to function entry if async
// preempted.
PCDATA_RestartAtEntry = -5
_PCDATA_START_VAL = -1
)
var emptyByte byte
// Pcvalue is the program count corresponding to the value Val
// WARN: we use relative value here (to function entry)
type Pcvalue struct {
PC uint32 // program count relative to function entry
Val int32 // value relative to the value in function entry
}
// Pcdata represents pc->value mapping table.
// WARN: we use ** [Pcdata[i].PC, Pcdata[i+1].PC) **
// as the range where the Pcdata[i].Val is effective.
type Pcdata []Pcvalue
// see https://docs.google.com/document/d/1lyPIbmsYbXnpNj57a261hgOYVpNRcgydurVQIyZOz_o/pub
func (self Pcdata) MarshalBinary() (data []byte, err error) {
// delta value always starts from -1
sv := int32(_PCDATA_START_VAL)
sp := uint32(0)
buf := make([]byte, binary.MaxVarintLen32)
for _, v := range self {
if v.PC < sp {
panic("PC must be in ascending order!")
}
dp := uint64(v.PC - sp)
dv := int64(v.Val - sv)
if dv == 0 || dp == 0 {
continue
}
n := binary.PutVarint(buf, dv)
data = append(data, buf[:n]...)
n2 := binary.PutUvarint(buf, dp)
data = append(data, buf[:n2]...)
sp = v.PC
sv = v.Val
}
// put 0 to indicate ends
data = append(data, 0)
return
}
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