gtsocial-umbx

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pcdata.go (2560B)

      1 /**
      2  * Copyright 2023 ByteDance Inc.
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *     http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package loader
     18 
     19 const (
     20     _N_PCDATA   = 4
     21 
     22     _PCDATA_UnsafePoint   = 0
     23     _PCDATA_StackMapIndex = 1
     24     _PCDATA_InlTreeIndex  = 2
     25     _PCDATA_ArgLiveIndex  = 3
     26 
     27     _PCDATA_INVALID_OFFSET = 0
     28 )
     29 
     30 const (
     31     // PCDATA_UnsafePoint values.
     32     PCDATA_UnsafePointSafe   = -1 // Safe for async preemption
     33     PCDATA_UnsafePointUnsafe = -2 // Unsafe for async preemption
     34 
     35     // PCDATA_Restart1(2) apply on a sequence of instructions, within
     36     // which if an async preemption happens, we should back off the PC
     37     // to the start of the sequence when resume.
     38     // We need two so we can distinguish the start/end of the sequence
     39     // in case that two sequences are next to each other.
     40     PCDATA_Restart1 = -3
     41     PCDATA_Restart2 = -4
     42 
     43     // Like PCDATA_RestartAtEntry, but back to function entry if async
     44     // preempted.
     45     PCDATA_RestartAtEntry = -5
     46 
     47     _PCDATA_START_VAL = -1
     48 )
     49 
     50 var emptyByte byte
     51 
     52 func encodeValue(v int) []byte {
     53     return encodeVariant(toZigzag(v))
     54 }
     55 
     56 func toZigzag(v int) int {
     57     return (v << 1) ^ (v >> 31)
     58 }
     59 
     60 func encodeVariant(v int) []byte {
     61     var u int
     62     var r []byte
     63 
     64     /* split every 7 bits */
     65     for v > 127 {
     66         u = v & 0x7f
     67         v = v >> 7
     68         r = append(r, byte(u) | 0x80)
     69     }
     70 
     71     /* check for last one */
     72     if v == 0 {
     73         return r
     74     }
     75 
     76     /* add the last one */
     77     r = append(r, byte(v))
     78     return r
     79 }
     80 
     81 type Pcvalue struct {
     82     PC  uint32 // PC offset from func entry
     83     Val int32
     84 }
     85 
     86 type Pcdata []Pcvalue
     87 
     88 // see https://docs.google.com/document/d/1lyPIbmsYbXnpNj57a261hgOYVpNRcgydurVQIyZOz_o/pub
     89 func (self Pcdata) MarshalBinary() (data []byte, err error) {
     90     // delta value always starts from -1
     91     sv := int32(_PCDATA_START_VAL)
     92     sp := uint32(0)
     93     for _, v := range self {
     94         data = append(data, encodeVariant(toZigzag(int(v.Val - sv)))...)
     95         data = append(data, encodeVariant(int(v.PC - sp))...)
     96         sp = v.PC
     97         sv = v.Val
     98     }
     99     return
    100 }