mirror of https://github.com/golang/go.git
cmd/internal/gc: clean up Componentgen
Update #9855 In preparation for introducing direct use of a zero register on platforms that support it, take the opportunity to clean up Componentgen a bit. Change-Id: I120ce1ffcca8c4f7603bfe76bfa1aedd27ebb4d2 Reviewed-on: https://go-review.googlesource.com/8691 Run-TryBot: Dave Cheney <dave@cheney.net> Reviewed-by: Minux Ma <minux@golang.org>
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Dave Cheney
parent
a1f57598cc
commit
4b21be4670
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@ -1116,26 +1116,16 @@ func checklabels() {
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}
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}
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/*
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* copy a composite value by moving its individual components.
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* Slices, strings and interfaces are supported.
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* Small structs or arrays with elements of basic type are
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* also supported.
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* nr is N when assigning a zero value.
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* return 1 if can do, 0 if can't.
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*/
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// Componentgen copies a composite value by moving its individual components.
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// Slices, strings and interfaces are supported. Small structs or arrays with
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// elements of basic type are also supported.
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// nr is nil when assigning a zero value.
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func Componentgen(nr *Node, nl *Node) bool {
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var nodl Node
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var nodr Node
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freel := 0
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freer := 0
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var isConstString bool
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var nodl, nodr Node
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switch nl.Type.Etype {
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default:
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goto no
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return false
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case TARRAY:
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t := nl.Type
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@ -1150,16 +1140,16 @@ func Componentgen(nr *Node, nl *Node) bool {
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break
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}
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goto no
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return false
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// Small structs with non-fat types are ok.
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// Zero-sized structs are treated separately elsewhere.
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case TSTRUCT:
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// Small structs with non-fat types are ok.
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// Zero-sized structs are treated separately elsewhere.
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fldcount := int64(0)
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for t := nl.Type.Type; t != nil; t = t.Down {
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if Isfat(t.Type) && !Isslice(t) {
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goto no
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return false
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}
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if t.Etype != TFIELD {
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Fatal("componentgen: not a TFIELD: %v", Tconv(t, obj.FmtLong))
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@ -1168,28 +1158,28 @@ func Componentgen(nr *Node, nl *Node) bool {
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}
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if fldcount == 0 || fldcount > 4 {
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goto no
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return false
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}
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case TSTRING, TINTER:
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break
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}
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isConstString = Isconst(nr, CTSTR)
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isConstString := Isconst(nr, CTSTR)
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nodl = *nl
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if !cadable(nl) {
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if nr != nil && !cadable(nr) && !isConstString {
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goto no
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return false
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}
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Igen(nl, &nodl, nil)
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freel = 1
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defer Regfree(&nodl)
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}
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if nr != nil {
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nodr = *nr
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if !cadable(nr) && !isConstString {
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Igen(nr, &nodr, nil)
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freer = 1
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defer Regfree(&nodr)
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}
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} else {
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// When zeroing, prepare a register containing zero.
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@ -1198,7 +1188,7 @@ func Componentgen(nr *Node, nl *Node) bool {
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Regalloc(&nodr, Types[TUINT], nil)
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Thearch.Gmove(&tmp, &nodr)
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freer = 1
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defer Regfree(&nodr)
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}
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// nl and nr are 'cadable' which basically means they are names (variables) now.
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@ -1206,12 +1196,15 @@ func Componentgen(nr *Node, nl *Node) bool {
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// VARDEF we generate will mark the old value as dead incorrectly.
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// (And also the assignments are useless.)
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if nr != nil && nl.Op == ONAME && nr.Op == ONAME && nl == nr {
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goto yes
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return true
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}
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switch nl.Type.Etype {
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// componentgen for arrays.
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default:
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return false
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case TARRAY:
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// componentgen for arrays.
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if nl.Op == ONAME {
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Gvardef(nl)
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}
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@ -1228,8 +1221,7 @@ func Componentgen(nr *Node, nl *Node) bool {
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nodl.Xoffset += t.Type.Width
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nodr.Xoffset += t.Type.Width
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}
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goto yes
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return true
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}
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// componentgen for slices.
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@ -1263,8 +1255,7 @@ func Componentgen(nr *Node, nl *Node) bool {
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}
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Thearch.Gmove(&nodr, &nodl)
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goto yes
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return true
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case TSTRING:
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if nl.Op == ONAME {
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@ -1297,8 +1288,7 @@ func Componentgen(nr *Node, nl *Node) bool {
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}
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Thearch.Gmove(&nodr, &nodl)
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goto yes
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return true
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case TINTER:
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if nl.Op == ONAME {
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@ -1323,8 +1313,7 @@ func Componentgen(nr *Node, nl *Node) bool {
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}
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Thearch.Gmove(&nodr, &nodl)
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goto yes
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return true
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case TSTRUCT:
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if nl.Op == ONAME {
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@ -1353,27 +1342,8 @@ func Componentgen(nr *Node, nl *Node) bool {
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Thearch.Gmove(&nodr, &nodl)
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}
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}
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goto yes
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return true
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}
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no:
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if freer != 0 {
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Regfree(&nodr)
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}
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if freel != 0 {
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Regfree(&nodl)
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}
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return false
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yes:
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if freer != 0 {
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Regfree(&nodr)
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}
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if freel != 0 {
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Regfree(&nodl)
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}
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return true
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}
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func cadable(n *Node) bool {
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