cmd/compile/internal/gc: remove OCMPIFACE and OCMPSTR

Interface and string comparisons don't need separate Ops any more than
struct or array comparisons do.

Removing them requires shuffling some code around in walk (and a
little in order), but overall allows simplifying things a bit.

Passes toolstash-check.

Change-Id: I084b8a6c089b768dc76d220379f4daed8a35db15
Reviewed-on: https://go-review.googlesource.com/c/141637
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/gc/const.go

@@ -1058,9 +1058,7 @@ func idealkind(n *Node) Ctype {
 		OLT,
 		ONE,
 		ONOT,
-		OOROR,
-		OCMPSTR,
-		OCMPIFACE:
+		OOROR:
 		return CTBOOL
 
 		// shifts (beware!).

src/cmd/compile/internal/gc/fmt.go

@@ -1146,8 +1146,6 @@ var opprec = []int{
 	OGE:           4,
 	OGT:           4,
 	ONE:           4,
-	OCMPSTR:       4,
-	OCMPIFACE:     4,
 	OSEND:         3,
 	OANDAND:       2,
 	OOROR:         1,
@@ -1507,11 +1505,6 @@ func (n *Node) exprfmt(s fmt.State, prec int, mode fmtMode) {
 			n1.exprfmt(s, nprec, mode)
 		}
 
-	case OCMPSTR, OCMPIFACE:
-		n.Left.exprfmt(s, nprec, mode)
-		mode.Fprintf(s, " %#v ", n.SubOp())
-		n.Right.exprfmt(s, nprec+1, mode)
-
 	default:
 		mode.Fprintf(s, "<node %v>", n.Op)
 	}

src/cmd/compile/internal/gc/iexport.go

@@ -1319,12 +1319,6 @@ func (w *exportWriter) expr(n *Node) {
 		w.pos(n.Pos)
 		w.exprList(n.List)
 
-	case OCMPSTR, OCMPIFACE:
-		w.op(n.SubOp())
-		w.pos(n.Pos)
-		w.expr(n.Left)
-		w.expr(n.Right)
-
 	case ODCLCONST:
 		// if exporting, DCLCONST should just be removed as its usage
 		// has already been replaced with literals

src/cmd/compile/internal/gc/iimport.go

@@ -935,9 +935,6 @@ func (r *importReader) node() *Node {
 		}
 		return x
 
-	// case OCMPSTR, OCMPIFACE:
-	// 	unreachable - mapped to std comparison operators by exporter
-
 	// --------------------------------------------------------------------
 	// statements
 	case ODCL:

src/cmd/compile/internal/gc/order.go

@@ -1010,20 +1010,6 @@ func (o *Order) expr(n, lhs *Node) *Node {
 			}
 		}
 
-	case OCMPSTR:
-		n.Left = o.expr(n.Left, nil)
-		n.Right = o.expr(n.Right, nil)
-
-		// Mark string(byteSlice) arguments to reuse byteSlice backing
-		// buffer during conversion. String comparison does not
-		// memorize the strings for later use, so it is safe.
-		if n.Left.Op == OARRAYBYTESTR {
-			n.Left.Op = OARRAYBYTESTRTMP
-		}
-		if n.Right.Op == OARRAYBYTESTR {
-			n.Right.Op = OARRAYBYTESTRTMP
-		}
-
 		// key must be addressable
 	case OINDEXMAP:
 		n.Left = o.expr(n.Left, nil)
@@ -1181,11 +1167,24 @@ func (o *Order) expr(n, lhs *Node) *Node {
 		n.Left = o.expr(n.Left, nil)
 		n = o.copyExpr(n, n.Type, true)
 
-	case OEQ, ONE:
+	case OEQ, ONE, OLT, OLE, OGT, OGE:
 		n.Left = o.expr(n.Left, nil)
 		n.Right = o.expr(n.Right, nil)
+
 		t := n.Left.Type
-		if t.IsStruct() || t.IsArray() {
+		switch {
+		case t.IsString():
+			// Mark string(byteSlice) arguments to reuse byteSlice backing
+			// buffer during conversion. String comparison does not
+			// memorize the strings for later use, so it is safe.
+			if n.Left.Op == OARRAYBYTESTR {
+				n.Left.Op = OARRAYBYTESTRTMP
+			}
+			if n.Right.Op == OARRAYBYTESTR {
+				n.Right.Op = OARRAYBYTESTRTMP
+			}
+
+		case t.IsStruct() || t.IsArray():
 			// for complex comparisons, we need both args to be
 			// addressable so we can pass them to the runtime.
 			n.Left = o.addrTemp(n.Left)

src/cmd/compile/internal/gc/syntax.go

@@ -65,7 +65,7 @@ func (n *Node) ResetAux() {
 
 func (n *Node) SubOp() Op {
 	switch n.Op {
-	case OASOP, OCMPIFACE, OCMPSTR, ONAME:
+	case OASOP, ONAME:
 	default:
 		Fatalf("unexpected op: %v", n.Op)
 	}
@@ -74,7 +74,7 @@ func (n *Node) SubOp() Op {
 
 func (n *Node) SetSubOp(op Op) {
 	switch n.Op {
-	case OASOP, OCMPIFACE, OCMPSTR, ONAME:
+	case OASOP, ONAME:
 	default:
 		Fatalf("unexpected op: %v", n.Op)
 	}
@@ -610,8 +610,8 @@ const (
 	OCAP             // cap(Left)
 	OCLOSE           // close(Left)
 	OCLOSURE         // func Type { Body } (func literal)
-	OCMPIFACE        // Left Etype Right (interface comparison, x == y or x != y)
-	OCMPSTR          // Left Etype Right (string comparison, x == y, x < y, etc)
+	_                // toolstash kludge; was OCMPIFACE
+	_                // toolstash kludge; was OCMPSTR
 	OCOMPLIT         // Right{List} (composite literal, not yet lowered to specific form)
 	OMAPLIT          // Type{List} (composite literal, Type is map)
 	OSTRUCTLIT       // Type{List} (composite literal, Type is struct)

src/cmd/compile/internal/gc/typecheck.go

@@ -747,12 +747,7 @@ func typecheck1(n *Node, top int) *Node {
 			}
 		}
 
-		if et == TSTRING {
-			if iscmp[n.Op] {
-				ot := n.Op
-				n.Op = OCMPSTR
-				n.SetSubOp(ot)
-			} else if n.Op == OADD {
+		if et == TSTRING && n.Op == OADD {
 			// create OADDSTR node with list of strings in x + y + z + (w + v) + ...
 			n.Op = OADDSTR
 
@@ -769,22 +764,6 @@ func typecheck1(n *Node, top int) *Node {
 			n.Left = nil
 			n.Right = nil
 		}
-		}
-
-		if et == TINTER {
-			if l.Op == OLITERAL && l.Val().Ctype() == CTNIL {
-				// swap for back end
-				n.Left = r
-
-				n.Right = l
-			} else if r.Op == OLITERAL && r.Val().Ctype() == CTNIL {
-			} else // leave alone for back end
-			if r.Type.IsInterface() == l.Type.IsInterface() {
-				ot := n.Op
-				n.Op = OCMPIFACE
-				n.SetSubOp(ot)
-			}
-		}
 
 		if (op == ODIV || op == OMOD) && Isconst(r, CTINT) {
 			if r.Val().U.(*Mpint).CmpInt64(0) == 0 {