[Modules] Add 'freestanding' to the 'requires-declaration' feature-list.

This adds support for modules that require (non-)freestanding
environment, such as the compiler builtin mm_malloc submodule.

Differential Revision: https://reviews.llvm.org/D23871

llvm-svn: 280613

clang/docs/Modules.rst

@@ -413,6 +413,9 @@ cplusplus
 cplusplus11
   C++11 support is available.
 
+freestanding
+  A freestanding environment is available.
+
 gnuinlineasm
   GNU inline ASM is available.
 

clang/lib/Basic/Module.cpp

@@ -64,6 +64,7 @@ static bool hasFeature(StringRef Feature, const LangOptions &LangOpts,
                         .Case("blocks", LangOpts.Blocks)
                         .Case("cplusplus", LangOpts.CPlusPlus)
                         .Case("cplusplus11", LangOpts.CPlusPlus11)
+                        .Case("freestanding", LangOpts.Freestanding)
                         .Case("gnuinlineasm", LangOpts.GNUAsm)
                         .Case("objc", LangOpts.ObjC1)
                         .Case("objc_arc", LangOpts.ObjCAutoRefCount)

clang/lib/Headers/module.modulemap

@@ -63,6 +63,7 @@ module _Builtin_intrinsics [system] [extern_c] {
     textual header "mwaitxintrin.h"
 
     explicit module mm_malloc {
+      requires !freestanding
       header "mm_malloc.h"
       export * // note: for <stdlib.h> dependency
     }

clang/test/Modules/compiler_builtins_x86.c

@@ -0,0 +1,6 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -fsyntax-only -fmodules -fimplicit-module-maps -fmodules-cache-path=%t %s -verify -ffreestanding
+// expected-no-diagnostics
+
+#include<x86intrin.h>
+