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trace.go
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trace.go
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// Copyright 2023 Sneller, 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 vm
import (
"io"
"sync"
"sync/atomic"
)
var (
tracing atomic.Uint32
tracelock sync.Mutex
traceout io.Writer
)
// TraceFlags is set of tracing options
// that can be passed to Trace.
type TraceFlags uint
const (
// TraceSSAText causes all compiled SSA programs
// to be dumped in their textual representation.
TraceSSAText = 1 << iota
// TraceSSADot causes all compiled SSA programs
// to be dumped in a format suitable for processing
// with graphviz(1).
TraceSSADot
// TraceBytecodeText causes all compiled bytecode
// programs to be dumped in a text-based format.
TraceBytecodeText
)
// Trace enables or disables tracing of bytecode
// program compilation.
//
// To enable tracing, Trace should be called with
// a non-nil io.Writer and non-zero flags.
// To disable tracing, Trace should be called
// with a nil io.Writer and flags equal to zero.
func Trace(w io.Writer, flags TraceFlags) {
if (w == nil) != (flags == 0) {
panic("invalid arguments for vm.Trace")
}
tracelock.Lock()
defer tracelock.Unlock()
traceout = w
tracing.Store(uint32(flags))
}
func enabled(flags TraceFlags) bool {
return TraceFlags(tracing.Load())&flags != 0
}
func trace(body func(io.Writer)) {
tracelock.Lock()
defer tracelock.Unlock()
if traceout == nil {
return // could have raced if we inspected flags before locking
}
body(traceout)
}