[dev.regabi] cmd/compile: remove uses of dummy

Per https://developers.google.com/style/inclusive-documentation,
since we are editing some of this code anyway and it is easier
to put the cleanup in a separate CL.

Change-Id: Ib6b851f43f9cc0a57676564477d4ff22abb1cee5
Reviewed-on: https://go-review.googlesource.com/c/go/+/273106
Trust: Russ Cox <rsc@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

15 files changed, 100 insertions, 101 deletions

diff --git a/src/cmd/compile/internal/gc/align.go b/src/cmd/compile/internal/gc/align.go
index 1f7631d199..563bd5030c 100644
--- a/src/cmd/compile/internal/gc/align.go
+++ b/src/cmd/compile/internal/gc/align.go
@@ -392,7 +392,7 @@ func dowidth(t *types.Type) {
 		w = 1 // anything will do
 
 	case TANY:
-		// dummy type; should be replaced before use.
+		// not a real type; should be replaced before use.
 		Fatalf("dowidth any")
 
 	case TSTRING:
diff --git a/src/cmd/compile/internal/gc/escape.go b/src/cmd/compile/internal/gc/escape.go
index 497151d02f..50674e1a1a 100644
--- a/src/cmd/compile/internal/gc/escape.go
+++ b/src/cmd/compile/internal/gc/escape.go
@@ -574,7 +574,7 @@ func (e *Escape) exprSkipInit(k EscHole, n *Node) {
 		// parameters all flow to the heap.
 		//
 		// TODO(mdempsky): Change ks into a callback, so that
-		// we don't have to create this dummy slice?
+		// we don't have to create this slice?
 		var ks []EscHole
 		for i := m.Type.NumResults(); i > 0; i-- {
 			ks = append(ks, e.heapHole())
diff --git a/src/cmd/compile/internal/gc/init.go b/src/cmd/compile/internal/gc/init.go
index ec9cc4bddc..c3b66a2ad2 100644
--- a/src/cmd/compile/internal/gc/init.go
+++ b/src/cmd/compile/internal/gc/init.go
@@ -15,8 +15,9 @@ import (
 // the name, normally "pkg.init", is altered to "pkg.init.0".
 var renameinitgen int
 
-// Dummy function for autotmps generated during typechecking.
-var dummyInitFn = nod(ODCLFUNC, nil, nil)
+// Function collecting autotmps generated during typechecking,
+// to be included in the package-level init function.
+var initTodo = nod(ODCLFUNC, nil, nil)
 
 func renameinit() *types.Sym {
 	s := lookupN("init.", renameinitgen)
@@ -46,11 +47,11 @@ func fninit(n []*Node) {
 		lineno = nf[0].Pos // prolog/epilog gets line number of first init stmt
 		initializers := lookup("init")
 		fn := dclfunc(initializers, nod(OTFUNC, nil, nil))
-		for _, dcl := range dummyInitFn.Func.Dcl {
+		for _, dcl := range initTodo.Func.Dcl {
 			dcl.Name.Curfn = fn
 		}
-		fn.Func.Dcl = append(fn.Func.Dcl, dummyInitFn.Func.Dcl...)
-		dummyInitFn.Func.Dcl = nil
+		fn.Func.Dcl = append(fn.Func.Dcl, initTodo.Func.Dcl...)
+		initTodo.Func.Dcl = nil
 
 		fn.Nbody.Set(nf)
 		funcbody()
@@ -62,13 +63,13 @@ func fninit(n []*Node) {
 		xtop = append(xtop, fn)
 		fns = append(fns, initializers.Linksym())
 	}
-	if dummyInitFn.Func.Dcl != nil {
-		// We only generate temps using dummyInitFn if there
+	if initTodo.Func.Dcl != nil {
+		// We only generate temps using initTodo if there
 		// are package-scope initialization statements, so
 		// something's weird if we get here.
-		Fatalf("dummyInitFn still has declarations")
+		Fatalf("initTodo still has declarations")
 	}
-	dummyInitFn = nil
+	initTodo = nil
 
 	// Record user init functions.
 	for i := 0; i < renameinitgen; i++ {
@@ -88,7 +89,7 @@ func fninit(n []*Node) {
 	// Make an .inittask structure.
 	sym := lookup(".inittask")
 	nn := newname(sym)
-	nn.Type = types.Types[TUINT8] // dummy type
+	nn.Type = types.Types[TUINT8] // fake type
 	nn.SetClass(PEXTERN)
 	sym.Def = asTypesNode(nn)
 	exportsym(nn)
diff --git a/src/cmd/compile/internal/gc/main.go b/src/cmd/compile/internal/gc/main.go
index fca1334a19..428bf31fa9 100644
--- a/src/cmd/compile/internal/gc/main.go
+++ b/src/cmd/compile/internal/gc/main.go
@@ -1254,9 +1254,7 @@ func importfile(f constant.Value) *types.Pkg {
 		}
 	}
 
-	// In the importfile, if we find:
-	// $$\n  (textual format): not supported anymore
-	// $$B\n (binary format) : import directly, then feed the lexer a dummy statement
+	// Expect $$B\n to signal binary import format.
 
 	// look for $$
 	var c byte
diff --git a/src/cmd/compile/internal/gc/pgen.go b/src/cmd/compile/internal/gc/pgen.go
index 0f0f6b7107..7c1d5543e3 100644
--- a/src/cmd/compile/internal/gc/pgen.go
+++ b/src/cmd/compile/internal/gc/pgen.go
@@ -459,7 +459,7 @@ func debuginfo(fnsym *obj.LSym, infosym *obj.LSym, curfn interface{}) ([]dwarf.S
 	decls, dwarfVars := createDwarfVars(fnsym, isODCLFUNC, fn.Func, apdecls)
 
 	// For each type referenced by the functions auto vars but not
-	// already referenced by a dwarf var, attach a dummy relocation to
+	// already referenced by a dwarf var, attach an R_USETYPE relocation to
 	// the function symbol to insure that the type included in DWARF
 	// processing during linking.
 	typesyms := []*obj.LSym{}
diff --git a/src/cmd/compile/internal/gc/phi.go b/src/cmd/compile/internal/gc/phi.go
index 5218cd0ef3..4beaa11a7e 100644
--- a/src/cmd/compile/internal/gc/phi.go
+++ b/src/cmd/compile/internal/gc/phi.go
@@ -59,7 +59,7 @@ type phiState struct {
 	hasDef *sparseSet   // has a write of the variable we're processing
 
 	// miscellaneous
-	placeholder *ssa.Value // dummy value to use as a "not set yet" placeholder.
+	placeholder *ssa.Value // value to use as a "not set yet" placeholder.
 }
 
 func (s *phiState) insertPhis() {
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 7a8dda2938..f196bee4a2 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -692,10 +692,10 @@ func (s *state) Warnl(pos src.XPos, msg string, args ...interface{}) { s.f.Warnl
 func (s *state) Debug_checknil() bool                                { return s.f.Frontend().Debug_checknil() }
 
 var (
-	// dummy node for the memory variable
+	// marker node for the memory variable
 	memVar = Node{Op: ONAME, Sym: &types.Sym{Name: "mem"}}
 
-	// dummy nodes for temporary variables
+	// marker nodes for temporary variables
 	ptrVar       = Node{Op: ONAME, Sym: &types.Sym{Name: "ptr"}}
 	lenVar       = Node{Op: ONAME, Sym: &types.Sym{Name: "len"}}
 	newlenVar    = Node{Op: ONAME, Sym: &types.Sym{Name: "newlen"}}
@@ -4793,7 +4793,7 @@ func (s *state) getMethodClosure(fn *Node) *ssa.Value {
 	n2.SetClass(PFUNC)
 	// n2.Sym already existed, so it's already marked as a function.
 	n2.Pos = fn.Pos
-	n2.Type = types.Types[TUINT8] // dummy type for a static closure. Could use runtime.funcval if we had it.
+	n2.Type = types.Types[TUINT8] // fake type for a static closure. Could use runtime.funcval if we had it.
 	return s.expr(n2)
 }
 
@@ -6054,7 +6054,7 @@ func (s *state) mem() *ssa.Value {
 
 func (s *state) addNamedValue(n *Node, v *ssa.Value) {
 	if n.Class() == Pxxx {
-		// Don't track our dummy nodes (&memVar etc.).
+		// Don't track our marker nodes (&memVar etc.).
 		return
 	}
 	if n.IsAutoTmp() {
diff --git a/src/cmd/compile/internal/gc/typecheck.go b/src/cmd/compile/internal/gc/typecheck.go
index d1bc781a54..9cc1dee773 100644
--- a/src/cmd/compile/internal/gc/typecheck.go
+++ b/src/cmd/compile/internal/gc/typecheck.go
@@ -2153,11 +2153,11 @@ func typecheckargs(n *Node) {
 	// If we're outside of function context, then this call will
 	// be executed during the generated init function. However,
 	// init.go hasn't yet created it. Instead, associate the
-	// temporary variables with dummyInitFn for now, and init.go
+	// temporary variables with initTodo for now, and init.go
 	// will reassociate them later when it's appropriate.
 	static := Curfn == nil
 	if static {
-		Curfn = dummyInitFn
+		Curfn = initTodo
 	}
 	for _, f := range t.FieldSlice() {
 		t := temp(f.Type)
diff --git a/src/cmd/compile/internal/ssa/export_test.go b/src/cmd/compile/internal/ssa/export_test.go
index b4c3e5cfdf..bfe94ff160 100644
--- a/src/cmd/compile/internal/ssa/export_test.go
+++ b/src/cmd/compile/internal/ssa/export_test.go
@@ -36,10 +36,10 @@ func testConfigArch(tb testing.TB, arch string) *Conf {
 		tb.Fatalf("unknown arch %s", arch)
 	}
 	if ctxt.Arch.PtrSize != 8 {
-		tb.Fatal("dummyTypes is 64-bit only")
+		tb.Fatal("testTypes is 64-bit only")
 	}
 	c := &Conf{
-		config: NewConfig(arch, dummyTypes, ctxt, true),
+		config: NewConfig(arch, testTypes, ctxt, true),
 		tb:     tb,
 	}
 	return c
@@ -53,108 +53,108 @@ type Conf struct {
 
 func (c *Conf) Frontend() Frontend {
 	if c.fe == nil {
-		c.fe = DummyFrontend{t: c.tb, ctxt: c.config.ctxt}
+		c.fe = TestFrontend{t: c.tb, ctxt: c.config.ctxt}
 	}
 	return c.fe
 }
 
-// DummyFrontend is a test-only frontend.
+// TestFrontend is a test-only frontend.
 // It assumes 64 bit integers and pointers.
-type DummyFrontend struct {
+type TestFrontend struct {
 	t    testing.TB
 	ctxt *obj.Link
 }
 
-type DummyAuto struct {
+type TestAuto struct {
 	t *types.Type
 	s string
 }
 
-func (d *DummyAuto) Typ() *types.Type {
+func (d *TestAuto) Typ() *types.Type {
 	return d.t
 }
 
-func (d *DummyAuto) String() string {
+func (d *TestAuto) String() string {
 	return d.s
 }
 
-func (d *DummyAuto) StorageClass() StorageClass {
+func (d *TestAuto) StorageClass() StorageClass {
 	return ClassAuto
 }
 
-func (d *DummyAuto) IsSynthetic() bool {
+func (d *TestAuto) IsSynthetic() bool {
 	return false
 }
 
-func (d *DummyAuto) IsAutoTmp() bool {
+func (d *TestAuto) IsAutoTmp() bool {
 	return true
 }
 
-func (DummyFrontend) StringData(s string) *obj.LSym {
+func (TestFrontend) StringData(s string) *obj.LSym {
 	return nil
 }
-func (DummyFrontend) Auto(pos src.XPos, t *types.Type) GCNode {
-	return &DummyAuto{t: t, s: "aDummyAuto"}
+func (TestFrontend) Auto(pos src.XPos, t *types.Type) GCNode {
+	return &TestAuto{t: t, s: "aTestAuto"}
 }
-func (d DummyFrontend) SplitString(s LocalSlot) (LocalSlot, LocalSlot) {
-	return LocalSlot{N: s.N, Type: dummyTypes.BytePtr, Off: s.Off}, LocalSlot{N: s.N, Type: dummyTypes.Int, Off: s.Off + 8}
+func (d TestFrontend) SplitString(s LocalSlot) (LocalSlot, LocalSlot) {
+	return LocalSlot{N: s.N, Type: testTypes.BytePtr, Off: s.Off}, LocalSlot{N: s.N, Type: testTypes.Int, Off: s.Off + 8}
 }
-func (d DummyFrontend) SplitInterface(s LocalSlot) (LocalSlot, LocalSlot) {
-	return LocalSlot{N: s.N, Type: dummyTypes.BytePtr, Off: s.Off}, LocalSlot{N: s.N, Type: dummyTypes.BytePtr, Off: s.Off + 8}
+func (d TestFrontend) SplitInterface(s LocalSlot) (LocalSlot, LocalSlot) {
+	return LocalSlot{N: s.N, Type: testTypes.BytePtr, Off: s.Off}, LocalSlot{N: s.N, Type: testTypes.BytePtr, Off: s.Off + 8}
 }
-func (d DummyFrontend) SplitSlice(s LocalSlot) (LocalSlot, LocalSlot, LocalSlot) {
+func (d TestFrontend) SplitSlice(s LocalSlot) (LocalSlot, LocalSlot, LocalSlot) {
 	return LocalSlot{N: s.N, Type: s.Type.Elem().PtrTo(), Off: s.Off},
-		LocalSlot{N: s.N, Type: dummyTypes.Int, Off: s.Off + 8},
-		LocalSlot{N: s.N, Type: dummyTypes.Int, Off: s.Off + 16}
+		LocalSlot{N: s.N, Type: testTypes.Int, Off: s.Off + 8},
+		LocalSlot{N: s.N, Type: testTypes.Int, Off: s.Off + 16}
 }
-func (d DummyFrontend) SplitComplex(s LocalSlot) (LocalSlot, LocalSlot) {
+func (d TestFrontend) SplitComplex(s LocalSlot) (LocalSlot, LocalSlot) {
 	if s.Type.Size() == 16 {
-		return LocalSlot{N: s.N, Type: dummyTypes.Float64, Off: s.Off}, LocalSlot{N: s.N, Type: dummyTypes.Float64, Off: s.Off + 8}
+		return LocalSlot{N: s.N, Type: testTypes.Float64, Off: s.Off}, LocalSlot{N: s.N, Type: testTypes.Float64, Off: s.Off + 8}
 	}
-	return LocalSlot{N: s.N, Type: dummyTypes.Float32, Off: s.Off}, LocalSlot{N: s.N, Type: dummyTypes.Float32, Off: s.Off + 4}
+	return LocalSlot{N: s.N, Type: testTypes.Float32, Off: s.Off}, LocalSlot{N: s.N, Type: testTypes.Float32, Off: s.Off + 4}
 }
-func (d DummyFrontend) SplitInt64(s LocalSlot) (LocalSlot, LocalSlot) {
+func (d TestFrontend) SplitInt64(s LocalSlot) (LocalSlot, LocalSlot) {
 	if s.Type.IsSigned() {
-		return LocalSlot{N: s.N, Type: dummyTypes.Int32, Off: s.Off + 4}, LocalSlot{N: s.N, Type: dummyTypes.UInt32, Off: s.Off}
+		return LocalSlot{N: s.N, Type: testTypes.Int32, Off: s.Off + 4}, LocalSlot{N: s.N, Type: testTypes.UInt32, Off: s.Off}
 	}
-	return LocalSlot{N: s.N, Type: dummyTypes.UInt32, Off: s.Off + 4}, LocalSlot{N: s.N, Type: dummyTypes.UInt32, Off: s.Off}
+	return LocalSlot{N: s.N, Type: testTypes.UInt32, Off: s.Off + 4}, LocalSlot{N: s.N, Type: testTypes.UInt32, Off: s.Off}
 }
-func (d DummyFrontend) SplitStruct(s LocalSlot, i int) LocalSlot {
+func (d TestFrontend) SplitStruct(s LocalSlot, i int) LocalSlot {
 	return LocalSlot{N: s.N, Type: s.Type.FieldType(i), Off: s.Off + s.Type.FieldOff(i)}
 }
-func (d DummyFrontend) SplitArray(s LocalSlot) LocalSlot {
+func (d TestFrontend) SplitArray(s LocalSlot) LocalSlot {
 	return LocalSlot{N: s.N, Type: s.Type.Elem(), Off: s.Off}
 }
 
-func (d DummyFrontend) SplitSlot(parent *LocalSlot, suffix string, offset int64, t *types.Type) LocalSlot {
+func (d TestFrontend) SplitSlot(parent *LocalSlot, suffix string, offset int64, t *types.Type) LocalSlot {
 	return LocalSlot{N: parent.N, Type: t, Off: offset}
 }
-func (DummyFrontend) Line(_ src.XPos) string {
+func (TestFrontend) Line(_ src.XPos) string {
 	return "unknown.go:0"
 }
-func (DummyFrontend) AllocFrame(f *Func) {
+func (TestFrontend) AllocFrame(f *Func) {
 }
-func (d DummyFrontend) Syslook(s string) *obj.LSym {
+func (d TestFrontend) Syslook(s string) *obj.LSym {
 	return d.ctxt.Lookup(s)
 }
-func (DummyFrontend) UseWriteBarrier() bool {
+func (TestFrontend) UseWriteBarrier() bool {
 	return true // only writebarrier_test cares
 }
-func (DummyFrontend) SetWBPos(pos src.XPos) {
+func (TestFrontend) SetWBPos(pos src.XPos) {
 }
 
-func (d DummyFrontend) Logf(msg string, args ...interface{}) { d.t.Logf(msg, args...) }
-func (d DummyFrontend) Log() bool                            { return true }
+func (d TestFrontend) Logf(msg string, args ...interface{}) { d.t.Logf(msg, args...) }
+func (d TestFrontend) Log() bool                            { return true }
 
-func (d DummyFrontend) Fatalf(_ src.XPos, msg string, args ...interface{}) { d.t.Fatalf(msg, args...) }
-func (d DummyFrontend) Warnl(_ src.XPos, msg string, args ...interface{})  { d.t.Logf(msg, args...) }
-func (d DummyFrontend) Debug_checknil() bool                               { return false }
+func (d TestFrontend) Fatalf(_ src.XPos, msg string, args ...interface{}) { d.t.Fatalf(msg, args...) }
+func (d TestFrontend) Warnl(_ src.XPos, msg string, args ...interface{})  { d.t.Logf(msg, args...) }
+func (d TestFrontend) Debug_checknil() bool                               { return false }
 
-func (d DummyFrontend) MyImportPath() string {
+func (d TestFrontend) MyImportPath() string {
 	return "my/import/path"
 }
 
-var dummyTypes Types
+var testTypes Types
 
 func init() {
 	// Initialize just enough of the universe and the types package to make our tests function.
@@ -198,12 +198,12 @@ func init() {
 		t.Align = uint8(typ.width)
 		types.Types[typ.et] = t
 	}
-	dummyTypes.SetTypPtrs()
+	testTypes.SetTypPtrs()
 }
 
-func (d DummyFrontend) DerefItab(sym *obj.LSym, off int64) *obj.LSym { return nil }
+func (d TestFrontend) DerefItab(sym *obj.LSym, off int64) *obj.LSym { return nil }
 
-func (d DummyFrontend) CanSSA(t *types.Type) bool {
-	// There are no un-SSAable types in dummy land.
+func (d TestFrontend) CanSSA(t *types.Type) bool {
+	// There are no un-SSAable types in test land.
 	return true
 }
diff --git a/src/cmd/compile/internal/ssa/poset.go b/src/cmd/compile/internal/ssa/poset.go
index f5a2b3a8c2..1e04b48ba4 100644
--- a/src/cmd/compile/internal/ssa/poset.go
+++ b/src/cmd/compile/internal/ssa/poset.go
@@ -136,13 +136,13 @@ type posetNode struct {
 // Most internal data structures are pre-allocated and flat, so for instance adding a
 // new relation does not cause any allocation. For performance reasons,
 // each node has only up to two outgoing edges (like a binary tree), so intermediate
-// "dummy" nodes are required to represent more than two relations. For instance,
+// "extra" nodes are required to represent more than two relations. For instance,
 // to record that A<I, A<J, A<K (with no known relation between I,J,K), we create the
 // following DAG:
 //
 //         A
 //        / \
-//       I  dummy
+//       I  extra
 //           /  \
 //          J    K
 //
@@ -223,7 +223,7 @@ func (po *poset) addchild(i1, i2 uint32, strict bool) {
 		po.setchr(i1, e2)
 		po.upush(undoSetChr, i1, 0)
 	} else {
-		// If n1 already has two children, add an intermediate dummy
+		// If n1 already has two children, add an intermediate extra
 		// node to record the relation correctly (without relating
 		// n2 to other existing nodes). Use a non-deterministic value
 		// to decide whether to append on the left or the right, to avoid
@@ -231,27 +231,27 @@ func (po *poset) addchild(i1, i2 uint32, strict bool) {
 		//
 		//      n1
 		//     /  \
-		//   i1l  dummy
+		//   i1l  extra
 		//        /   \
 		//      i1r   n2
 		//
-		dummy := po.newnode(nil)
+		extra := po.newnode(nil)
 		if (i1^i2)&1 != 0 { // non-deterministic
-			po.setchl(dummy, i1r)
-			po.setchr(dummy, e2)
-			po.setchr(i1, newedge(dummy, false))
+			po.setchl(extra, i1r)
+			po.setchr(extra, e2)
+			po.setchr(i1, newedge(extra, false))
 			po.upush(undoSetChr, i1, i1r)
 		} else {
-			po.setchl(dummy, i1l)
-			po.setchr(dummy, e2)
-			po.setchl(i1, newedge(dummy, false))
+			po.setchl(extra, i1l)
+			po.setchr(extra, e2)
+			po.setchl(i1, newedge(extra, false))
 			po.upush(undoSetChl, i1, i1l)
 		}
 	}
 }
 
 // newnode allocates a new node bound to SSA value n.
-// If n is nil, this is a dummy node (= only used internally).
+// If n is nil, this is an extra node (= only used internally).
 func (po *poset) newnode(n *Value) uint32 {
 	i := po.lastidx + 1
 	po.lastidx++
@@ -380,9 +380,9 @@ func (po *poset) newconst(n *Value) {
 
 	case higherptr != 0:
 		// Higher bound only. To record n < higher, we need
-		// a dummy root:
+		// an extra root:
 		//
-		//        dummy
+		//        extra
 		//        /   \
 		//      root   \
 		//       /      n
@@ -395,11 +395,11 @@ func (po *poset) newconst(n *Value) {
 		if r2 != po.roots[0] { // all constants should be in root #0
 			panic("constant not in root #0")
 		}
-		dummy := po.newnode(nil)
-		po.changeroot(r2, dummy)
-		po.upush(undoChangeRoot, dummy, newedge(r2, false))
-		po.addchild(dummy, r2, false)
-		po.addchild(dummy, i, false)
+		extra := po.newnode(nil)
+		po.changeroot(r2, extra)
+		po.upush(undoChangeRoot, extra, newedge(r2, false))
+		po.addchild(extra, r2, false)
+		po.addchild(extra, i, false)
 		po.addchild(i, i2, true)
 	}
 
@@ -612,7 +612,7 @@ func (po *poset) findroot(i uint32) uint32 {
 	panic("findroot didn't find any root")
 }
 
-// mergeroot merges two DAGs into one DAG by creating a new dummy root
+// mergeroot merges two DAGs into one DAG by creating a new extra root
 func (po *poset) mergeroot(r1, r2 uint32) uint32 {
 	// Root #0 is special as it contains all constants. Since mergeroot
 	// discards r2 as root and keeps r1, make sure that r2 is not root #0,
@@ -1004,7 +1004,7 @@ func (po *poset) setOrder(n1, n2 *Value, strict bool) bool {
 	case !f1 && f2:
 		// n1 is not in any DAG but n2 is. If n2 is a root, we can put
 		// n1 in its place as a root; otherwise, we need to create a new
-		// dummy root to record the relation.
+		// extra root to record the relation.
 		i1 = po.newnode(n1)
 
 		if po.isroot(i2) {
@@ -1020,17 +1020,17 @@ func (po *poset) setOrder(n1, n2 *Value, strict bool) bool {
 
 		// Re-parent as follows:
 		//
-		//                  dummy
+		//                  extra
 		//     r            /   \
 		//      \   ===>   r    i1
 		//      i2          \   /
 		//                    i2
 		//
-		dummy := po.newnode(nil)
-		po.changeroot(r, dummy)
-		po.upush(undoChangeRoot, dummy, newedge(r, false))
-		po.addchild(dummy, r, false)
-		po.addchild(dummy, i1, false)
+		extra := po.newnode(nil)
+		po.changeroot(r, extra)
+		po.upush(undoChangeRoot, extra, newedge(r, false))
+		po.addchild(extra, r, false)
+		po.addchild(extra, i1, false)
 		po.addchild(i1, i2, strict)
 
 	case f1 && f2:
diff --git a/src/cmd/compile/internal/ssa/regalloc.go b/src/cmd/compile/internal/ssa/regalloc.go
index 0339b073ae..4ed884c3e7 100644
--- a/src/cmd/compile/internal/ssa/regalloc.go
+++ b/src/cmd/compile/internal/ssa/regalloc.go
@@ -104,7 +104,7 @@
 // If b3 is the primary predecessor of b2, then we use x3 in b2 and
 // add a x4:CX->BX copy at the end of b4.
 // But the definition of x3 doesn't dominate b2.  We should really
-// insert a dummy phi at the start of b2 (x5=phi(x3,x4):BX) to keep
+// insert an extra phi at the start of b2 (x5=phi(x3,x4):BX) to keep
 // SSA form. For now, we ignore this problem as remaining in strict
 // SSA form isn't needed after regalloc. We'll just leave the use
 // of x3 not dominated by the definition of x3, and the CX->BX copy
diff --git a/src/cmd/compile/internal/syntax/dumper_test.go b/src/cmd/compile/internal/syntax/dumper_test.go
index f84bd2d705..22680dce78 100644
--- a/src/cmd/compile/internal/syntax/dumper_test.go
+++ b/src/cmd/compile/internal/syntax/dumper_test.go
@@ -13,7 +13,7 @@ func TestDump(t *testing.T) {
 		t.Skip("skipping test in short mode")
 	}
 
-	// provide a dummy error handler so parsing doesn't stop after first error
+	// provide a no-op error handler so parsing doesn't stop after first error
 	ast, err := ParseFile(*src_, func(error) {}, nil, CheckBranches)
 	if err != nil {
 		t.Error(err)
diff --git a/src/cmd/compile/internal/syntax/nodes.go b/src/cmd/compile/internal/syntax/nodes.go
index 815630fcd4..487cab19fe 100644
--- a/src/cmd/compile/internal/syntax/nodes.go
+++ b/src/cmd/compile/internal/syntax/nodes.go
@@ -114,7 +114,7 @@ func (*decl) aDecl() {}
 
 // All declarations belonging to the same group point to the same Group node.
 type Group struct {
-	dummy int // not empty so we are guaranteed different Group instances
+	_ int // not empty so we are guaranteed different Group instances
 }
 
 // ----------------------------------------------------------------------------
diff --git a/src/cmd/compile/internal/syntax/printer_test.go b/src/cmd/compile/internal/syntax/printer_test.go
index c3b9aca229..fe72e7a374 100644
--- a/src/cmd/compile/internal/syntax/printer_test.go
+++ b/src/cmd/compile/internal/syntax/printer_test.go
@@ -18,7 +18,7 @@ func TestPrint(t *testing.T) {
 		t.Skip("skipping test in short mode")
 	}
 
-	// provide a dummy error handler so parsing doesn't stop after first error
+	// provide a no-op error handler so parsing doesn't stop after first error
 	ast, err := ParseFile(*src_, func(error) {}, nil, 0)
 	if err != nil {
 		t.Error(err)
diff --git a/src/cmd/compile/internal/types/type.go b/src/cmd/compile/internal/types/type.go
index f1a01b64da..b93409aac1 100644
--- a/src/cmd/compile/internal/types/type.go
+++ b/src/cmd/compile/internal/types/type.go
@@ -10,7 +10,7 @@ import (
 	"fmt"
 )
 
-// Dummy Node so we can refer to *Node without actually
+// Our own “Node” so we can refer to *gc.Node without actually
 // having a gc.Node. Necessary to break import cycles.
 // TODO(gri) try to eliminate soon
 type Node struct{ _ int }