[dev.ssa] cmd/compile/internal/ssa: Add dummy frontend for testing.

Change-Id: Ica26c0297ac7afeb0b5b668cf5f5cd1667c6cc43
Reviewed-on: https://go-review.googlesource.com/10699Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

src/cmd/compile/internal/ssa/deadcode_test.go

@@ -7,7 +7,7 @@ package ssa
 import "testing"
 
 func TestDeadLoop(t *testing.T) {
-	c := NewConfig("amd64")
+	c := NewConfig("amd64", DummyFrontend{})
 	fun := Fun(c, "entry",
 		Bloc("entry",
 			Valu("mem", OpArg, TypeMem, ".mem"),
@@ -37,7 +37,7 @@ func TestDeadLoop(t *testing.T) {
 }
 
 func TestDeadValue(t *testing.T) {
-	c := NewConfig("amd64")
+	c := NewConfig("amd64", DummyFrontend{})
 	fun := Fun(c, "entry",
 		Bloc("entry",
 			Valu("mem", OpArg, TypeMem, ".mem"),
@@ -60,7 +60,7 @@ func TestDeadValue(t *testing.T) {
 }
 
 func TestNeverTaken(t *testing.T) {
-	c := NewConfig("amd64")
+	c := NewConfig("amd64", DummyFrontend{})
 	fun := Fun(c, "entry",
 		Bloc("entry",
 			Valu("cond", OpConst, TypeBool, false),

src/cmd/compile/internal/ssa/export_test.go

@@ -8,3 +8,9 @@ var CheckFunc = checkFunc
 var PrintFunc = printFunc
 var Opt = opt
 var Deadcode = deadcode
+
+type DummyFrontend struct{}
+
+func (d DummyFrontend) StringSym(s string) interface{} {
+	return nil
+}

src/cmd/compile/internal/ssa/func_test.go

@@ -257,7 +257,7 @@ func addEdge(b, c *Block) {
 }
 
 func TestArgs(t *testing.T) {
-	c := NewConfig("amd64")
+	c := NewConfig("amd64", DummyFrontend{})
 	fun := Fun(c, "entry",
 		Bloc("entry",
 			Valu("a", OpConst, TypeInt64, 14),
@@ -277,7 +277,7 @@ func TestArgs(t *testing.T) {
 }
 
 func TestEquiv(t *testing.T) {
-	c := NewConfig("amd64")
+	c := NewConfig("amd64", DummyFrontend{})
 	equivalentCases := []struct{ f, g fun }{
 		// simple case
 		{