100 lines
2.5 KiB
Go
100 lines
2.5 KiB
Go
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/**
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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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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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func encodeValue(v int) []byte {
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return encodeVariant(toZigzag(v))
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}
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func toZigzag(v int) int {
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return (v << 1) ^ (v >> 31)
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}
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func encodeVariant(v int) []byte {
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var u int
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var r []byte
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/* split every 7 bits */
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for v > 127 {
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u = v & 0x7f
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v = v >> 7
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r = append(r, byte(u) | 0x80)
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}
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/* check for last one */
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if v == 0 {
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return r
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}
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/* add the last one */
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r = append(r, byte(v))
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return r
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}
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type Pcvalue struct {
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PC uint32 // PC offset from func entry
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Val int32
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}
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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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for _, v := range self {
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data = append(data, encodeVariant(toZigzag(int(v.Val - sv)))...)
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data = append(data, encodeVariant(int(v.PC - sp))...)
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sp = v.PC
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sv = v.Val
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}
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return
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}
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