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