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149671dfc3
Implement a simple common-subexpression elimination. It uses value numbering & a dominator tree to detect redundant computation. Change-Id: Id0ff775e439c22f4d41bdd5976176017dd2a2086 Reviewed-on: https://go-review.googlesource.com/8172 Reviewed-by: Alan Donovan <adonovan@google.com>
42 lines
1.1 KiB
Go
42 lines
1.1 KiB
Go
// Copyright 2015 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 ssa
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var (
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// TODO(khr): put arch configuration constants together somewhere
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intSize = 8
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ptrSize = 8
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)
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//go:generate go run rulegen/rulegen.go rulegen/lower_amd64.rules lowerAmd64 lowerAmd64.go
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// convert to machine-dependent ops
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func lower(f *Func) {
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// repeat rewrites until we find no more rewrites
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// TODO: pick the target arch from config
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applyRewrite(f, lowerAmd64)
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// TODO: check for unlowered opcodes, fail if we find one
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// additional pass for 386/amd64, link condition codes directly to blocks
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// TODO: do generically somehow? Special "block" rewrite rules?
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for _, b := range f.Blocks {
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switch b.Kind {
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case BlockIf:
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switch b.Control.Op {
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case OpSETL:
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b.Kind = BlockLT
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b.Control = b.Control.Args[0]
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// TODO: others
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}
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case BlockLT:
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if b.Control.Op == OpInvertFlags {
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b.Kind = BlockGE
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b.Control = b.Control.Args[0]
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}
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// TODO: others
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}
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}
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}
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