[turbofan] Add basic support for calling to (a subset of) C functions.

src/compiler/instruction-selector.cc

Index: src/compiler/instruction-selector.cc
diff --git a/src/compiler/instruction-selector.cc b/src/compiler/instruction-selector.cc
index e7ca5e2532c531d48de6fc9309edc283c6c72fb5..eb638ad8bb010de8264d07a48d91394acdca2aa7 100644
--- a/src/compiler/instruction-selector.cc
+++ b/src/compiler/instruction-selector.cc
@@ -336,8 +336,7 @@ void InstructionSelector::InitializeCallBuffer(Node* call, CallBuffer* buffer,
     case CallDescriptor::kCallAddress:
       buffer->instruction_args.push_back(
           (call_address_immediate &&
-           (callee->opcode() == IrOpcode::kInt32Constant ||
-            callee->opcode() == IrOpcode::kInt64Constant))
+           callee->opcode() == IrOpcode::kExternalConstant)
               ? g.UseImmediate(callee)
               : g.UseRegister(callee));
       break;