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2954f11ead
This CL adds a simple framework for augmenting the current export data format by writing out additional data *after* the existing data, with an extra header before it that current readers ignore. In particular, this is used by unified IR to be able to experiment and iterate on export data designs without having to keep the go/internal/gcimporter and x/tools/go/gcexportdata importers in sync. Instead, they simply continue reading the existing data written out by typecheck/iexport.go. Change-Id: I883211c2892e2c7dec758b85ff6bc31b244440a0 Reviewed-on: https://go-review.googlesource.com/c/go/+/327169 Run-TryBot: Matthew Dempsky <mdempsky@google.com> Trust: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
65 lines
1.9 KiB
Go
65 lines
1.9 KiB
Go
// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package noder
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import (
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"bytes"
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"fmt"
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"io"
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"cmd/compile/internal/base"
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"cmd/compile/internal/typecheck"
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"cmd/internal/bio"
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)
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// writeNewExportFunc is a hook that can be added to append extra
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// export data after the normal export data section. It allows
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// experimenting with new export data format designs without requiring
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// immediate support in the go/internal or x/tools importers.
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var writeNewExportFunc func(out io.Writer)
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func WriteExports(out *bio.Writer) {
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// When unified IR exports are enable, we simply append it to the
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// end of the normal export data (with compiler extensions
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// disabled), and write an extra header giving its size.
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//
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// If the compiler sees this header, it knows to read the new data
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// instead; meanwhile the go/types importers will silently ignore it
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// and continue processing the old export instead.
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//
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// This allows us to experiment with changes to the new export data
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// format without needing to update the go/internal/gcimporter or
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// (worse) x/tools/go/gcexportdata.
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useNewExport := writeNewExportFunc != nil
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var old, new bytes.Buffer
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typecheck.WriteExports(&old, !useNewExport)
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if useNewExport {
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writeNewExportFunc(&new)
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}
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oldLen := old.Len()
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newLen := new.Len()
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if useNewExport {
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fmt.Fprintf(out, "\nnewexportsize %v\n", newLen)
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}
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// The linker also looks for the $$ marker - use char after $$ to distinguish format.
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out.WriteString("\n$$B\n") // indicate binary export format
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io.Copy(out, &old)
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out.WriteString("\n$$\n")
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io.Copy(out, &new)
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if base.Debug.Export != 0 {
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fmt.Printf("BenchmarkExportSize:%s 1 %d bytes\n", base.Ctxt.Pkgpath, oldLen)
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if useNewExport {
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fmt.Printf("BenchmarkNewExportSize:%s 1 %d bytes\n", base.Ctxt.Pkgpath, newLen)
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}
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}
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}
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