[compiler] Add relocatable pointer constants for wasm memory references.

src/compiler/instruction.h

Index: src/compiler/instruction.h
diff --git a/src/compiler/instruction.h b/src/compiler/instruction.h
index 9c978cee7c37543a40f791d14a730b6879c2edd2..d5755efdac1adb6013f2536efc4050ee6ff63340 100644
--- a/src/compiler/instruction.h
+++ b/src/compiler/instruction.h
@@ -930,9 +930,12 @@ class Constant final {
   explicit Constant(Handle<HeapObject> obj)
       : type_(kHeapObject), value_(bit_cast<intptr_t>(obj)) {}
   explicit Constant(RpoNumber rpo) : type_(kRpoNumber), value_(rpo.ToInt()) {}
+  explicit Constant(RelocatablePtrConstantInfo info);
 
   Type type() const { return type_; }
 
+  RelocInfo::Mode rmode() const { return rmode_; }
+
   int32_t ToInt32() const {
     DCHECK(type() == kInt32 || type() == kInt64);
     const int32_t value = static_cast<int32_t>(value_);
@@ -975,6 +978,7 @@ class Constant final {
  private:
   Type type_;
   int64_t value_;
+  RelocInfo::Mode rmode_;
 };