mirror of
https://github.com/golang/go.git
synced 2025-12-08 06:10:04 +00:00
2083b5d673
This reduces the API surface of Type slightly (for #25056), but also makes it more consistent with the reflect and go/types APIs. Passes toolstash-check. Change-Id: Ief9a8eb461ae6e88895f347e2a1b7b8a62423222 Reviewed-on: https://go-review.googlesource.com/109138 Run-TryBot: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
536 lines
12 KiB
Go
536 lines
12 KiB
Go
// Copyright 2009 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 gc
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import (
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"cmd/compile/internal/types"
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"cmd/internal/objabi"
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"cmd/internal/sys"
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"unicode/utf8"
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)
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// range
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func typecheckrange(n *Node) {
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// Typechecking order is important here:
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// 0. first typecheck range expression (slice/map/chan),
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// it is evaluated only once and so logically it is not part of the loop.
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// 1. typcheck produced values,
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// this part can declare new vars and so it must be typechecked before body,
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// because body can contain a closure that captures the vars.
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// 2. decldepth++ to denote loop body.
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// 3. typecheck body.
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// 4. decldepth--.
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typecheckrangeExpr(n)
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// second half of dance, the first half being typecheckrangeExpr
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n.SetTypecheck(1)
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ls := n.List.Slice()
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for i1, n1 := range ls {
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if n1.Typecheck() == 0 {
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ls[i1] = typecheck(ls[i1], Erv|Easgn)
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}
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}
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decldepth++
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typecheckslice(n.Nbody.Slice(), Etop)
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decldepth--
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}
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func typecheckrangeExpr(n *Node) {
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n.Right = typecheck(n.Right, Erv)
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t := n.Right.Type
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if t == nil {
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return
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}
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// delicate little dance. see typecheckas2
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ls := n.List.Slice()
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for i1, n1 := range ls {
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if n1.Name == nil || n1.Name.Defn != n {
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ls[i1] = typecheck(ls[i1], Erv|Easgn)
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}
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}
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if t.IsPtr() && t.Elem().IsArray() {
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t = t.Elem()
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}
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n.Type = t
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var t1, t2 *types.Type
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toomany := false
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switch t.Etype {
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default:
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yyerrorl(n.Pos, "cannot range over %L", n.Right)
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return
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case TARRAY, TSLICE:
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t1 = types.Types[TINT]
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t2 = t.Elem()
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case TMAP:
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t1 = t.Key()
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t2 = t.Elem()
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case TCHAN:
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if !t.ChanDir().CanRecv() {
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yyerrorl(n.Pos, "invalid operation: range %v (receive from send-only type %v)", n.Right, n.Right.Type)
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return
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}
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t1 = t.Elem()
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t2 = nil
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if n.List.Len() == 2 {
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toomany = true
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}
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case TSTRING:
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t1 = types.Types[TINT]
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t2 = types.Runetype
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}
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if n.List.Len() > 2 || toomany {
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yyerrorl(n.Pos, "too many variables in range")
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}
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var v1, v2 *Node
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if n.List.Len() != 0 {
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v1 = n.List.First()
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}
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if n.List.Len() > 1 {
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v2 = n.List.Second()
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}
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// this is not only a optimization but also a requirement in the spec.
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// "if the second iteration variable is the blank identifier, the range
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// clause is equivalent to the same clause with only the first variable
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// present."
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if v2.isBlank() {
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if v1 != nil {
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n.List.Set1(v1)
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}
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v2 = nil
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}
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var why string
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if v1 != nil {
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if v1.Name != nil && v1.Name.Defn == n {
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v1.Type = t1
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} else if v1.Type != nil && assignop(t1, v1.Type, &why) == 0 {
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yyerrorl(n.Pos, "cannot assign type %v to %L in range%s", t1, v1, why)
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}
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checkassign(n, v1)
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}
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if v2 != nil {
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if v2.Name != nil && v2.Name.Defn == n {
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v2.Type = t2
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} else if v2.Type != nil && assignop(t2, v2.Type, &why) == 0 {
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yyerrorl(n.Pos, "cannot assign type %v to %L in range%s", t2, v2, why)
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}
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checkassign(n, v2)
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}
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}
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func cheapComputableIndex(width int64) bool {
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switch thearch.LinkArch.Family {
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// MIPS does not have R+R addressing
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// Arm64 may lack ability to generate this code in our assembler,
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// but the architecture supports it.
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case sys.PPC64, sys.S390X:
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return width == 1
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case sys.AMD64, sys.I386, sys.ARM64, sys.ARM:
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switch width {
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case 1, 2, 4, 8:
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return true
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}
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}
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return false
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}
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// walkrange transforms various forms of ORANGE into
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// simpler forms. The result must be assigned back to n.
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// Node n may also be modified in place, and may also be
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// the returned node.
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func walkrange(n *Node) *Node {
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// variable name conventions:
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// ohv1, hv1, hv2: hidden (old) val 1, 2
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// ha, hit: hidden aggregate, iterator
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// hn, hp: hidden len, pointer
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// hb: hidden bool
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// a, v1, v2: not hidden aggregate, val 1, 2
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t := n.Type
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a := n.Right
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lno := setlineno(a)
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n.Right = nil
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var v1, v2 *Node
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l := n.List.Len()
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if l > 0 {
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v1 = n.List.First()
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}
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if l > 1 {
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v2 = n.List.Second()
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}
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if v2.isBlank() {
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v2 = nil
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}
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if v1.isBlank() && v2 == nil {
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v1 = nil
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}
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if v1 == nil && v2 != nil {
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Fatalf("walkrange: v2 != nil while v1 == nil")
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}
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// n.List has no meaning anymore, clear it
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// to avoid erroneous processing by racewalk.
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n.List.Set(nil)
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var ifGuard *Node
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translatedLoopOp := OFOR
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var body []*Node
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var init []*Node
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switch t.Etype {
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default:
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Fatalf("walkrange")
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case TARRAY, TSLICE:
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if memclrrange(n, v1, v2, a) {
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lineno = lno
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return n
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}
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// orderstmt arranged for a copy of the array/slice variable if needed.
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ha := a
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hv1 := temp(types.Types[TINT])
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hn := temp(types.Types[TINT])
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init = append(init, nod(OAS, hv1, nil))
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init = append(init, nod(OAS, hn, nod(OLEN, ha, nil)))
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n.Left = nod(OLT, hv1, hn)
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n.Right = nod(OAS, hv1, nod(OADD, hv1, nodintconst(1)))
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// for range ha { body }
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if v1 == nil {
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break
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}
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// for v1 := range ha { body }
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if v2 == nil {
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body = []*Node{nod(OAS, v1, hv1)}
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break
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}
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// for v1, v2 := range ha { body }
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if cheapComputableIndex(n.Type.Elem().Width) {
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// v1, v2 = hv1, ha[hv1]
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tmp := nod(OINDEX, ha, hv1)
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tmp.SetBounded(true)
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// Use OAS2 to correctly handle assignments
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// of the form "v1, a[v1] := range".
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a := nod(OAS2, nil, nil)
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a.List.Set2(v1, v2)
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a.Rlist.Set2(hv1, tmp)
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body = []*Node{a}
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break
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}
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if objabi.Preemptibleloops_enabled != 0 {
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// Doing this transformation makes a bounds check removal less trivial; see #20711
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// TODO enhance the preemption check insertion so that this transformation is not necessary.
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ifGuard = nod(OIF, nil, nil)
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ifGuard.Left = nod(OLT, hv1, hn)
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translatedLoopOp = OFORUNTIL
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}
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hp := temp(types.NewPtr(n.Type.Elem()))
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tmp := nod(OINDEX, ha, nodintconst(0))
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tmp.SetBounded(true)
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init = append(init, nod(OAS, hp, nod(OADDR, tmp, nil)))
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// Use OAS2 to correctly handle assignments
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// of the form "v1, a[v1] := range".
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a := nod(OAS2, nil, nil)
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a.List.Set2(v1, v2)
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a.Rlist.Set2(hv1, nod(OIND, hp, nil))
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body = append(body, a)
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// Advance pointer as part of increment.
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// We used to advance the pointer before executing the loop body,
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// but doing so would make the pointer point past the end of the
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// array during the final iteration, possibly causing another unrelated
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// piece of memory not to be garbage collected until the loop finished.
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// Advancing during the increment ensures that the pointer p only points
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// pass the end of the array during the final "p++; i++; if(i >= len(x)) break;",
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// after which p is dead, so it cannot confuse the collector.
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tmp = nod(OADD, hp, nodintconst(t.Elem().Width))
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tmp.Type = hp.Type
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tmp.SetTypecheck(1)
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tmp.Right.Type = types.Types[types.Tptr]
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tmp.Right.SetTypecheck(1)
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a = nod(OAS, hp, tmp)
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a = typecheck(a, Etop)
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n.Right.Ninit.Set1(a)
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case TMAP:
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// orderstmt allocated the iterator for us.
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// we only use a once, so no copy needed.
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ha := a
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hit := prealloc[n]
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th := hit.Type
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n.Left = nil
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keysym := th.Field(0).Sym // depends on layout of iterator struct. See reflect.go:hiter
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valsym := th.Field(1).Sym // ditto
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fn := syslook("mapiterinit")
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fn = substArgTypes(fn, t.Key(), t.Elem(), th)
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init = append(init, mkcall1(fn, nil, nil, typename(t), ha, nod(OADDR, hit, nil)))
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n.Left = nod(ONE, nodSym(ODOT, hit, keysym), nodnil())
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fn = syslook("mapiternext")
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fn = substArgTypes(fn, th)
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n.Right = mkcall1(fn, nil, nil, nod(OADDR, hit, nil))
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key := nodSym(ODOT, hit, keysym)
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key = nod(OIND, key, nil)
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if v1 == nil {
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body = nil
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} else if v2 == nil {
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body = []*Node{nod(OAS, v1, key)}
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} else {
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val := nodSym(ODOT, hit, valsym)
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val = nod(OIND, val, nil)
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a := nod(OAS2, nil, nil)
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a.List.Set2(v1, v2)
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a.Rlist.Set2(key, val)
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body = []*Node{a}
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}
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case TCHAN:
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// orderstmt arranged for a copy of the channel variable.
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ha := a
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n.Left = nil
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hv1 := temp(t.Elem())
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hv1.SetTypecheck(1)
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if types.Haspointers(t.Elem()) {
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init = append(init, nod(OAS, hv1, nil))
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}
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hb := temp(types.Types[TBOOL])
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n.Left = nod(ONE, hb, nodbool(false))
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a := nod(OAS2RECV, nil, nil)
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a.SetTypecheck(1)
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a.List.Set2(hv1, hb)
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a.Rlist.Set1(nod(ORECV, ha, nil))
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n.Left.Ninit.Set1(a)
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if v1 == nil {
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body = nil
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} else {
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body = []*Node{nod(OAS, v1, hv1)}
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}
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// Zero hv1. This prevents hv1 from being the sole, inaccessible
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// reference to an otherwise GC-able value during the next channel receive.
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// See issue 15281.
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body = append(body, nod(OAS, hv1, nil))
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case TSTRING:
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// Transform string range statements like "for v1, v2 = range a" into
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//
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// ha := a
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// for hv1 := 0; hv1 < len(ha); {
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// hv1t := hv1
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// hv2 := rune(ha[hv1])
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// if hv2 < utf8.RuneSelf {
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// hv1++
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// } else {
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// hv2, hv1 = decoderune(ha, hv1)
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// }
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// v1, v2 = hv1t, hv2
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// // original body
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// }
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// orderstmt arranged for a copy of the string variable.
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ha := a
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hv1 := temp(types.Types[TINT])
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hv1t := temp(types.Types[TINT])
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hv2 := temp(types.Runetype)
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// hv1 := 0
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init = append(init, nod(OAS, hv1, nil))
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// hv1 < len(ha)
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n.Left = nod(OLT, hv1, nod(OLEN, ha, nil))
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if v1 != nil {
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// hv1t = hv1
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body = append(body, nod(OAS, hv1t, hv1))
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}
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// hv2 := rune(ha[hv1])
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nind := nod(OINDEX, ha, hv1)
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nind.SetBounded(true)
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body = append(body, nod(OAS, hv2, conv(nind, types.Runetype)))
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// if hv2 < utf8.RuneSelf
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nif := nod(OIF, nil, nil)
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nif.Left = nod(OLT, hv2, nodintconst(utf8.RuneSelf))
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// hv1++
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nif.Nbody.Set1(nod(OAS, hv1, nod(OADD, hv1, nodintconst(1))))
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// } else {
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eif := nod(OAS2, nil, nil)
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nif.Rlist.Set1(eif)
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// hv2, hv1 = decoderune(ha, hv1)
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eif.List.Set2(hv2, hv1)
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fn := syslook("decoderune")
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eif.Rlist.Set1(mkcall1(fn, fn.Type.Results(), nil, ha, hv1))
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body = append(body, nif)
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if v1 != nil {
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if v2 != nil {
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// v1, v2 = hv1t, hv2
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a := nod(OAS2, nil, nil)
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a.List.Set2(v1, v2)
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a.Rlist.Set2(hv1t, hv2)
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body = append(body, a)
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} else {
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// v1 = hv1t
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body = append(body, nod(OAS, v1, hv1t))
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}
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}
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}
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n.Op = translatedLoopOp
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typecheckslice(init, Etop)
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if ifGuard != nil {
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ifGuard.Ninit.Append(init...)
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ifGuard = typecheck(ifGuard, Etop)
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} else {
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n.Ninit.Append(init...)
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}
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typecheckslice(n.Left.Ninit.Slice(), Etop)
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n.Left = typecheck(n.Left, Erv)
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n.Left = defaultlit(n.Left, nil)
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n.Right = typecheck(n.Right, Etop)
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typecheckslice(body, Etop)
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n.Nbody.Prepend(body...)
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if ifGuard != nil {
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ifGuard.Nbody.Set1(n)
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n = ifGuard
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}
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n = walkstmt(n)
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lineno = lno
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return n
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}
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// Lower n into runtime·memclr if possible, for
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// fast zeroing of slices and arrays (issue 5373).
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// Look for instances of
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//
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// for i := range a {
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// a[i] = zero
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// }
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//
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// in which the evaluation of a is side-effect-free.
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//
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// Parameters are as in walkrange: "for v1, v2 = range a".
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func memclrrange(n, v1, v2, a *Node) bool {
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if Debug['N'] != 0 || instrumenting {
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return false
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}
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if v1 == nil || v2 != nil {
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return false
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}
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if n.Nbody.Len() == 0 || n.Nbody.First() == nil || n.Nbody.Len() > 1 {
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return false
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}
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stmt := n.Nbody.First() // only stmt in body
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if stmt.Op != OAS || stmt.Left.Op != OINDEX {
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return false
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}
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if !samesafeexpr(stmt.Left.Left, a) || !samesafeexpr(stmt.Left.Right, v1) {
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return false
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}
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elemsize := n.Type.Elem().Width
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if elemsize <= 0 || !isZero(stmt.Right) {
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return false
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}
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// Convert to
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// if len(a) != 0 {
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// hp = &a[0]
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// hn = len(a)*sizeof(elem(a))
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// memclr{NoHeap,Has}Pointers(hp, hn)
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// i = len(a) - 1
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// }
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n.Op = OIF
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n.Nbody.Set(nil)
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n.Left = nod(ONE, nod(OLEN, a, nil), nodintconst(0))
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// hp = &a[0]
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hp := temp(types.Types[TUNSAFEPTR])
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tmp := nod(OINDEX, a, nodintconst(0))
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tmp.SetBounded(true)
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tmp = nod(OADDR, tmp, nil)
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tmp = nod(OCONVNOP, tmp, nil)
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tmp.Type = types.Types[TUNSAFEPTR]
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n.Nbody.Append(nod(OAS, hp, tmp))
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// hn = len(a) * sizeof(elem(a))
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hn := temp(types.Types[TUINTPTR])
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tmp = nod(OLEN, a, nil)
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tmp = nod(OMUL, tmp, nodintconst(elemsize))
|
|
tmp = conv(tmp, types.Types[TUINTPTR])
|
|
n.Nbody.Append(nod(OAS, hn, tmp))
|
|
|
|
var fn *Node
|
|
if types.Haspointers(a.Type.Elem()) {
|
|
// memclrHasPointers(hp, hn)
|
|
fn = mkcall("memclrHasPointers", nil, nil, hp, hn)
|
|
} else {
|
|
// memclrNoHeapPointers(hp, hn)
|
|
fn = mkcall("memclrNoHeapPointers", nil, nil, hp, hn)
|
|
}
|
|
|
|
n.Nbody.Append(fn)
|
|
|
|
// i = len(a) - 1
|
|
v1 = nod(OAS, v1, nod(OSUB, nod(OLEN, a, nil), nodintconst(1)))
|
|
|
|
n.Nbody.Append(v1)
|
|
|
|
n.Left = typecheck(n.Left, Erv)
|
|
n.Left = defaultlit(n.Left, nil)
|
|
typecheckslice(n.Nbody.Slice(), Etop)
|
|
n = walkstmt(n)
|
|
return true
|
|
}
|