Store decls in prototypes on the declarator instead of in the AST

This saves two pointers from FunctionDecl that were being used for some
rare and questionable C-only functionality.  The DeclsInPrototypeScope
ArrayRef was added in r151712 in order to parse this kind of C code:

    enum e {x, y};
    int f(enum {y, x} n) {
     return x; // should return 1, not 0
    }

The challenge is that we parse 'int f(enum {y, x} n)' it its own
function prototype scope that gets popped before we build the
FunctionDecl for 'f'. The original change was doing two questionable
things:

1. Saving all tag decls introduced in prototype scope on a TU-global
Sema variable. This is problematic when you have cases like this, where
'x' and 'y' shouldn't be visible in 'f':
    void f(void (*fp)(enum { x, y } e)) { /* no x */ }
This patch fixes that, so now 'f' can't see 'x', which is consistent
with GCC.

2. Storing the decls in FunctionDecl in ActOnFunctionDeclarator so that
they could be used in ActOnStartOfFunctionDef. This is just an
inefficient way to move information around. The AST lives forever, but
the list of non-parameter decls in prototype scope is short lived.

Moving these things to the Declarator solves both of these issues.

Reviewers: rsmith

Subscribers: jmolloy, cfe-commits

Differential Revision: https://reviews.llvm.org/D27279

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@289225 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 27 insertions, 0 deletions

diff --git a/test/PCH/decl-in-prototype.c b/test/PCH/decl-in-prototype.c
new file mode 100644
index 0000000000..6ee4b3d5eb
--- /dev/null
+++ b/test/PCH/decl-in-prototype.c
@@ -0,0 +1,27 @@
+// Test that we serialize the enum decl in the function prototype somehow.
+// These decls aren't serialized quite the same way as parameters.
+
+// Test this without pch.
+// RUN: %clang_cc1 -include %s -emit-llvm -o - %s | FileCheck %s
+
+// Test with pch.
+// RUN: %clang_cc1 -emit-pch -o %t %s
+// RUN: %clang_cc1 -include-pch %t -emit-llvm -o - %s | FileCheck %s
+
+// CHECK-LABEL: define i32 @main()
+// CHECK:   ret i32 1
+
+#ifndef HEADER
+#define HEADER
+
+static inline __attribute__((always_inline)) f(enum { x, y } p) {
+  return y;
+}
+
+#else
+
+int main() {
+  return f(0);
+}
+
+#endif