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>
diff --git a/src/cmd/internal/gc/gen.go b/src/cmd/internal/gc/gen.go
index 4b7344a..fde0a19 100644
--- a/src/cmd/internal/gc/gen.go
+++ b/src/cmd/internal/gc/gen.go
@@ -1116,26 +1116,16 @@
}
}
-/*
- * copy a composite value by moving its individual components.
- * Slices, strings and interfaces are supported.
- * Small structs or arrays with elements of basic type are
- * also supported.
- * nr is N when assigning a zero value.
- * return 1 if can do, 0 if can't.
- */
+// Componentgen copies a composite value by moving its individual components.
+// Slices, strings and interfaces are supported. Small structs or arrays with
+// elements of basic type are also supported.
+// nr is nil when assigning a zero value.
func Componentgen(nr *Node, nl *Node) bool {
- var nodl Node
- var nodr Node
-
- freel := 0
- freer := 0
-
- var isConstString bool
+ var nodl, nodr Node
switch nl.Type.Etype {
default:
- goto no
+ return false
case TARRAY:
t := nl.Type
@@ -1150,16 +1140,16 @@
break
}
- goto no
+ return false
- // Small structs with non-fat types are ok.
- // Zero-sized structs are treated separately elsewhere.
case TSTRUCT:
+ // Small structs with non-fat types are ok.
+ // Zero-sized structs are treated separately elsewhere.
fldcount := int64(0)
for t := nl.Type.Type; t != nil; t = t.Down {
if Isfat(t.Type) && !Isslice(t) {
- goto no
+ return false
}
if t.Etype != TFIELD {
Fatal("componentgen: not a TFIELD: %v", Tconv(t, obj.FmtLong))
@@ -1168,28 +1158,28 @@
}
if fldcount == 0 || fldcount > 4 {
- goto no
+ return false
}
case TSTRING, TINTER:
break
}
- isConstString = Isconst(nr, CTSTR)
+ isConstString := Isconst(nr, CTSTR)
nodl = *nl
if !cadable(nl) {
if nr != nil && !cadable(nr) && !isConstString {
- goto no
+ return false
}
Igen(nl, &nodl, nil)
- freel = 1
+ defer Regfree(&nodl)
}
if nr != nil {
nodr = *nr
if !cadable(nr) && !isConstString {
Igen(nr, &nodr, nil)
- freer = 1
+ defer Regfree(&nodr)
}
} else {
// When zeroing, prepare a register containing zero.
@@ -1198,7 +1188,7 @@
Regalloc(&nodr, Types[TUINT], nil)
Thearch.Gmove(&tmp, &nodr)
- freer = 1
+ defer Regfree(&nodr)
}
// nl and nr are 'cadable' which basically means they are names (variables) now.
@@ -1206,12 +1196,15 @@
// VARDEF we generate will mark the old value as dead incorrectly.
// (And also the assignments are useless.)
if nr != nil && nl.Op == ONAME && nr.Op == ONAME && nl == nr {
- goto yes
+ return true
}
switch nl.Type.Etype {
- // componentgen for arrays.
+ default:
+ return false
+
case TARRAY:
+ // componentgen for arrays.
if nl.Op == ONAME {
Gvardef(nl)
}
@@ -1228,8 +1221,7 @@
nodl.Xoffset += t.Type.Width
nodr.Xoffset += t.Type.Width
}
-
- goto yes
+ return true
}
// componentgen for slices.
@@ -1263,8 +1255,7 @@
}
Thearch.Gmove(&nodr, &nodl)
-
- goto yes
+ return true
case TSTRING:
if nl.Op == ONAME {
@@ -1297,8 +1288,7 @@
}
Thearch.Gmove(&nodr, &nodl)
-
- goto yes
+ return true
case TINTER:
if nl.Op == ONAME {
@@ -1323,8 +1313,7 @@
}
Thearch.Gmove(&nodr, &nodl)
-
- goto yes
+ return true
case TSTRUCT:
if nl.Op == ONAME {
@@ -1353,27 +1342,8 @@
Thearch.Gmove(&nodr, &nodl)
}
}
-
- goto yes
+ return true
}
-
-no:
- if freer != 0 {
- Regfree(&nodr)
- }
- if freel != 0 {
- Regfree(&nodl)
- }
- return false
-
-yes:
- if freer != 0 {
- Regfree(&nodr)
- }
- if freel != 0 {
- Regfree(&nodl)
- }
- return true
}
func cadable(n *Node) bool {
