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[dev.regabi] cmd/compile: cleanup devirtualization docs

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Change-Id: I8e319f55fad6e9ed857aa020a96f3a89ccaadcea
Reviewed-on: https://go-review.googlesource.com/c/go/+/280213
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
This commit is contained in:
Matthew Dempsky 2020-12-24 16:03:47 -08:00
parent 4b1d0fe66f
commit 2785c691c2
1 changed files with 11 additions and 27 deletions
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38
src/cmd/compile/internal/devirtualize/devirtualize.go
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@ -1,29 +1,10 @@
// Copyright 2011 The Go Authors. All rights reserved.
// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//
// The inlining facility makes 2 passes: first caninl determines which
// functions are suitable for inlining, and for those that are it
// saves a copy of the body. Then inlcalls walks each function body to
// expand calls to inlinable functions.
//
// The Debug.l flag controls the aggressiveness. Note that main() swaps level 0 and 1,
// making 1 the default and -l disable. Additional levels (beyond -l) may be buggy and
// are not supported.
// 0: disabled
// 1: 80-nodes leaf functions, oneliners, panic, lazy typechecking (default)
// 2: (unassigned)
// 3: (unassigned)
// 4: allow non-leaf functions
//
// At some point this may get another default and become switch-offable with -N.
//
// The -d typcheckinl flag enables early typechecking of all imported bodies,
// which is useful to flush out bugs.
//
// The Debug.m flag enables diagnostic output. a single -m is useful for verifying
// which calls get inlined or not, more is for debugging, and may go away at any point.
// Package devirtualize implements a simple "devirtualization"
// optimization pass, which replaces interface method calls with
// direct concrete-type method calls where possible.
package devirtualize
import (
@ -33,18 +14,21 @@ import (
"cmd/compile/internal/types"
)
// Devirtualize replaces interface method calls within fn with direct
// concrete-type method calls where applicable.
// Func devirtualizes calls within fn where possible.
func Func(fn *ir.Func) {
ir.CurFunc = fn
ir.VisitList(fn.Body, func(n ir.Node) {
if n.Op() == ir.OCALLINTER {
Call(n.(*ir.CallExpr))
if call, ok := n.(*ir.CallExpr); ok {
Call(call)
}
})
}
// Call devirtualizes the given call if possible.
func Call(call *ir.CallExpr) {
if call.Op() != ir.OCALLINTER {
return
}
sel := call.X.(*ir.SelectorExpr)
r := ir.StaticValue(sel.X)
if r.Op() != ir.OCONVIFACE {