IR: print value numbers for unnamed function arguments

For consistency with normal instructions and clarity when reading IR,
it's best to print the %0, %1, ... names of function arguments in
definitions.

Also modifies the parser to accept IR in that form for obvious reasons.

llvm-svn: 367755

clang/test/CXX/except/except.spec/p14-ir.cpp

@@ -26,12 +26,12 @@ struct X4 {
 struct X5 : X0, X4 { };
 
 void test(X2 x2, X3 x3, X5 x5) {
-  // CHECK: define linkonce_odr void @_ZN2X2C1ERKS_(%struct.X2* %this, %struct.X2* dereferenceable({{[0-9]+}})) unnamed_addr
+  // CHECK: define linkonce_odr void @_ZN2X2C1ERKS_(%struct.X2* %this, %struct.X2* dereferenceable({{[0-9]+}}) %0) unnamed_addr
   // CHECK:      call void @_ZN2X2C2ERKS_({{.*}}) [[NUW:#[0-9]+]]
   // CHECK-NEXT: ret void
   // CHECK-NEXT: }
   X2 x2a(x2);
-  // CHECK: define linkonce_odr void @_ZN2X3C1ERKS_(%struct.X3* %this, %struct.X3* dereferenceable({{[0-9]+}})) unnamed_addr
+  // CHECK: define linkonce_odr void @_ZN2X3C1ERKS_(%struct.X3* %this, %struct.X3* dereferenceable({{[0-9]+}}) %0) unnamed_addr
   // CHECK:      call void @_ZN2X3C2ERKS_({{.*}}) [[NUW]]
   // CHECK-NEXT: ret void
   // CHECK-NEXT: }