[Modules] Add platform feature to requires clause

[bruno]

Summary

Allows module map writers to add build requirements based on platform/os. Useful when target features and language dialects aren't enough to conditionalize building a module. Among other things, it also makes it more convenient for modules with the same name but different set of submodules to be described in the same module map.

rdar://problem/43909745

[aprantl]

docs/Modules.rst

470

Does this work with platforms+environment combinations, such as the ios simulator on Darwin?

[bruno]

Addressed Adrian's review. Added support to consider the environment and well the combination platform-environment. @aprantl also handled multiple variants of simulator combinations.

[aprantl]

docs/Modules.rst

470

Is iossimulator a thing? The triple is called x86_64-apple-ios-11.2.3-simulator and the SDK calls itself iphonesimulator, so I wonder if this shouldn't be called ios-simulator or iphonesimulator instead.

[aprantl]

lib/Basic/Module.cpp

101

Ah.. it looks like you are fully aware of this :-)

[rsmith]

docs/Modules.rst

475–476

What is the reason to allow these to be combined into a single feature name rather than treating them as two distinct features? (Eg, requires linux, gnueabi rather than requires linux-gnueabi)?

[bruno]

docs/Modules.rst

475–476

No specific reason other than the convenience of writing triple like requirements. But thinking more about it, it might make more sense to have it decoupled and written as a combination to avoid confusion. Will update the patch to reflect that.

[bruno]

Update patch after review.

[rsmith]

lib/Basic/Module.cpp

81

Comment is out of date.

docs/Modules.rst

opencl
   OpenCL is available
 
 tls
   Thread local storage is available.
 
 *target feature*
   A specific target feature (e.g., ``sse4``, ``avx``, ``neon``) is available.
 
+*platform variant*
+  A specific os/platform variant (e.g. ``ios``, ``macos``, ``android``, ``win32``, ``linux``, etc) is available.
 
 **Example:** The ``std`` module can be extended to also include C++ and C++11 headers using a *requires-declaration*:
 
 .. parsed-literal::
 
  module std {
     // C standard library...
 
     module vector {
       requires cplusplus
       header "vector"
     }
 
     module type_traits {

lib/Basic/Module.cpp

 
 /// Determine whether a translation unit built using the current
 /// language options has the given feature.
 static bool hasFeature(StringRef Feature, const LangOptions &LangOpts,
                        const TargetInfo &Target) {
   bool HasFeature = llvm::StringSwitch<bool>(Feature)
                         .Case("altivec", LangOpts.AltiVec)
                         .Case("blocks", LangOpts.Blocks)
                         .Case("coroutines", LangOpts.CoroutinesTS)
                         .Case("cplusplus", LangOpts.CPlusPlus)
                         .Case("cplusplus11", LangOpts.CPlusPlus11)
                         .Case("cplusplus14", LangOpts.CPlusPlus14)
                         .Case("cplusplus17", LangOpts.CPlusPlus17)
                         .Case("c99", LangOpts.C99)
                         .Case("c11", LangOpts.C11)
                         .Case("c17", LangOpts.C17)
                         .Case("freestanding", LangOpts.Freestanding)
                         .Case("gnuinlineasm", LangOpts.GNUAsm)
                         .Case("objc", LangOpts.ObjC1)
                         .Case("objc_arc", LangOpts.ObjCAutoRefCount)
                         .Case("opencl", LangOpts.OpenCL)
                         .Case("tls", Target.isTLSSupported())
                         .Case("zvector", LangOpts.ZVector)
-                        .Default(Target.hasFeature(Feature));
+                        .Default(Target.hasFeature(Feature) ||
+                                 Target.getPlatformName() == Feature);
   if (!HasFeature)
     HasFeature = std::find(LangOpts.ModuleFeatures.begin(),
                            LangOpts.ModuleFeatures.end(),
                            Feature) != LangOpts.ModuleFeatures.end();
   return HasFeature;
 }
 
 bool Module::isAvailable(const LangOptions &LangOpts, const TargetInfo &Target,
                          Requirement &Req,
                          UnresolvedHeaderDirective &MissingHeader,
                          Module *&ShadowingModule) const {
   if (IsAvailable)

test/Modules/target-platform-features.m

+// Clear and create directories
+// RUN: rm -rf %t
+// RUN: mkdir %t
+// RUN: mkdir %t/cache
+// RUN: mkdir %t/Inputs
+
+// Build module map file
+// RUN: echo "module RequiresMacOS {"     >> %t/Inputs/module.map
+// RUN: echo "  requires macos"   >> %t/Inputs/module.map
+// RUN: echo "}"                        >> %t/Inputs/module.map
+// RUN: echo "module RequiresNotiOS {"     >> %t/Inputs/module.map
+// RUN: echo "  requires !ios"   >> %t/Inputs/module.map
+// RUN: echo "}"                        >> %t/Inputs/module.map
+// RUN: echo "module RequiresMain {"     >> %t/Inputs/module.map
+// RUN: echo "  module SubRequiresNotiOS {"     >> %t/Inputs/module.map
+// RUN: echo "    requires !ios"   >> %t/Inputs/module.map
+// RUN: echo "  }"                        >> %t/Inputs/module.map
+// RUN: echo "}"                        >> %t/Inputs/module.map
+
+// RUN: %clang_cc1 -triple=x86_64-apple-macosx10.6 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t/cache -x objective-c -I%t/Inputs -verify %s -fblocks -fobjc-arc
+// expected-no-diagnostics
+
+// RUN: not %clang_cc1 -triple=arm64-apple-ios -fmodules -fimplicit-module-maps -fmodules-cache-path=%t/cache -x objective-c -I%t/Inputs %s -fblocks -fobjc-arc 2> %t.notios
+// RUN: FileCheck %s -check-prefix=CHECK-IOS < %t.notios
+
+// CHECK-IOS: module 'RequiresMacOS' requires feature 'macos'
+@import RequiresMacOS;
+// CHECK-IOS: module 'RequiresNotiOS' is incompatible with feature 'ios'
+@import RequiresNotiOS;
+
+// We should never get errors for submodules that don't match
+// CHECK-IOS-NOT: module 'RequiresMain'
+@import RequiresMain;