init repo

vendor/github.com/bytedance/sonic/loader/pcdata.go

@@ -0,0 +1,93 @@
+/**
+ * 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
+}