[dev.ssa] cmd/compiler/internal/ssa: Add auxint field

Add an additional int64 auxiliary field to Value.

There are two main reasons for doing this:
1) Ints in interfaces require allocation, and we store ints in Aux a lot.
2) I'd like to have both *gc.Sym and int offsets included in lots
   of operations (e.g. MOVQloadidx8).  It will be more efficient to
   store them as separate fields instead of a pointer to a sym/int pair.

It also simplifies a bunch of code.

This is just the refactoring.  I'll start using this some more in a
subsequent changelist.

Change-Id: I1ca797ff572553986cf90cab3ac0a0c1d01ad241
Reviewed-on: https://go-review.googlesource.com/10929
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
diff --git a/src/cmd/compile/internal/ssa/deadstore_test.go b/src/cmd/compile/internal/ssa/deadstore_test.go
index 70b2092..5143afb 100644
--- a/src/cmd/compile/internal/ssa/deadstore_test.go
+++ b/src/cmd/compile/internal/ssa/deadstore_test.go
@@ -13,13 +13,13 @@
 	ptrType := &TypeImpl{Size_: 8, Ptr: true, Name: "testptr"} // dummy for testing
 	fun := Fun(c, "entry",
 		Bloc("entry",
-			Valu("start", OpArg, TypeMem, ".mem"),
-			Valu("v", OpConst, TypeBool, true),
-			Valu("addr1", OpGlobal, ptrType, nil),
-			Valu("addr2", OpGlobal, ptrType, nil),
-			Valu("store1", OpStore, TypeMem, nil, "addr1", "v", "start"),
-			Valu("store2", OpStore, TypeMem, nil, "addr2", "v", "store1"),
-			Valu("store3", OpStore, TypeMem, nil, "addr1", "v", "store2"),
+			Valu("start", OpArg, TypeMem, 0, ".mem"),
+			Valu("v", OpConst, TypeBool, 0, true),
+			Valu("addr1", OpGlobal, ptrType, 0, nil),
+			Valu("addr2", OpGlobal, ptrType, 0, nil),
+			Valu("store1", OpStore, TypeMem, 0, nil, "addr1", "v", "start"),
+			Valu("store2", OpStore, TypeMem, 0, nil, "addr2", "v", "store1"),
+			Valu("store3", OpStore, TypeMem, 0, nil, "addr1", "v", "store2"),
 			Goto("exit")),
 		Bloc("exit",
 			Exit("store3")))
@@ -39,13 +39,13 @@
 	ptrType := &TypeImpl{Size_: 8, Ptr: true, Name: "testptr"} // dummy for testing
 	fun := Fun(c, "entry",
 		Bloc("entry",
-			Valu("start", OpArg, TypeMem, ".mem"),
-			Valu("v", OpConst, TypeBool, true),
-			Valu("addr", OpGlobal, ptrType, nil),
+			Valu("start", OpArg, TypeMem, 0, ".mem"),
+			Valu("v", OpConst, TypeBool, 0, true),
+			Valu("addr", OpGlobal, ptrType, 0, nil),
 			Goto("loop")),
 		Bloc("loop",
-			Valu("phi", OpPhi, TypeMem, nil, "start", "store"),
-			Valu("store", OpStore, TypeMem, nil, "addr", "v", "phi"),
+			Valu("phi", OpPhi, TypeMem, 0, nil, "start", "store"),
+			Valu("store", OpStore, TypeMem, 0, nil, "addr", "v", "phi"),
 			If("v", "loop", "exit")),
 		Bloc("exit",
 			Exit("store")))
@@ -65,12 +65,12 @@
 	t2 := &TypeImpl{Size_: 4, Ptr: true, Name: "t2"}
 	fun := Fun(c, "entry",
 		Bloc("entry",
-			Valu("start", OpArg, TypeMem, ".mem"),
-			Valu("v", OpConst, TypeBool, true),
-			Valu("addr1", OpGlobal, t1, nil),
-			Valu("addr2", OpGlobal, t2, nil),
-			Valu("store1", OpStore, TypeMem, nil, "addr1", "v", "start"),
-			Valu("store2", OpStore, TypeMem, nil, "addr2", "v", "store1"),
+			Valu("start", OpArg, TypeMem, 0, ".mem"),
+			Valu("v", OpConst, TypeBool, 0, true),
+			Valu("addr1", OpGlobal, t1, 0, nil),
+			Valu("addr2", OpGlobal, t2, 0, nil),
+			Valu("store1", OpStore, TypeMem, 0, nil, "addr1", "v", "start"),
+			Valu("store2", OpStore, TypeMem, 0, nil, "addr2", "v", "store1"),
 			Goto("exit")),
 		Bloc("exit",
 			Exit("store2")))