Add a PragmaHandler Registry for plugins to add PragmaHandlers to

This allows plugins which add AST passes to also define pragmas to do things
like only enable certain behaviour of the AST pass in files where a certain
pragma is used.

Differential Revision: http://reviews.llvm.org/D18319

llvm-svn: 265295

5 files changed, 89 insertions, 4 deletions

diff --git a/clang/docs/ClangPlugins.rst b/clang/docs/ClangPlugins.rst
index f83bb666a63..1b81bdeb7ac 100644
--- a/clang/docs/ClangPlugins.rst
+++ b/clang/docs/ClangPlugins.rst
@@ -43,6 +43,26 @@ register a plugin in a library, use ``FrontendPluginRegistry::Add<>``:
 
   static FrontendPluginRegistry::Add<MyPlugin> X("my-plugin-name", "my plugin description");
 
+Defining pragmas
+================
+
+Plugins can also define pragmas by declaring a ``PragmaHandler`` and
+registering it using ``PragmaHandlerRegistry::Add<>``:
+
+.. code-block:: c++
+
+  // Define a pragma handler for #pragma example_pragma
+  class ExamplePragmaHandler : public PragmaHandler {
+  public:
+    ExamplePragmaHandler() : PragmaHandler("example_pragma") { }
+    void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
+                      Token &PragmaTok) {
+      // Handle the pragma
+    }
+  };
+
+  static PragmaHandlerRegistry::Add<ExamplePragmaHandler> Y("example_pragma","example pragma description");
+
 Putting it all together
 =======================
 
diff --git a/clang/examples/AnnotateFunctions/AnnotateFunctions.cpp b/clang/examples/AnnotateFunctions/AnnotateFunctions.cpp
index f2e7322183a..375f18f8e09 100644
--- a/clang/examples/AnnotateFunctions/AnnotateFunctions.cpp
+++ b/clang/examples/AnnotateFunctions/AnnotateFunctions.cpp
@@ -7,20 +7,29 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// Example clang plugin which adds an annotation to every function.
+// Example clang plugin which adds an annotation to every function in
+// translation units that start with #pragma enable_annotate.
 //
 //===----------------------------------------------------------------------===//
 
 #include "clang/Frontend/FrontendPluginRegistry.h"
 #include "clang/AST/AST.h"
 #include "clang/AST/ASTConsumer.h"
+#include "clang/Lex/Preprocessor.h"
+#include "clang/Lex/LexDiagnostic.h"
 using namespace clang;
 
 namespace {
 
+static bool EnableAnnotate = false;
+static bool HandledDecl = false;
+
 class AnnotateFunctionsConsumer : public ASTConsumer {
 public:
   bool HandleTopLevelDecl(DeclGroupRef DG) override {
+    HandledDecl = true;
+    if (!EnableAnnotate)
+      return true;
     for (auto D : DG)
       if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
         FD->addAttr(AnnotateAttr::CreateImplicit(FD->getASTContext(),
@@ -46,7 +55,34 @@ public:
   }
 };
 
+class PragmaAnnotateHandler : public PragmaHandler {
+public:
+  PragmaAnnotateHandler() : PragmaHandler("enable_annotate") { }
+
+  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
+                    Token &PragmaTok) override {
+
+    Token Tok;
+    PP.LexUnexpandedToken(Tok);
+    if (Tok.isNot(tok::eod))
+      PP.Diag(Tok, diag::ext_pp_extra_tokens_at_eol) << "pragma";
+
+    if (HandledDecl) {
+      DiagnosticsEngine &D = PP.getDiagnostics();
+      unsigned ID = D.getCustomDiagID(
+        DiagnosticsEngine::Error,
+        "#pragma enable_annotate not allowed after declarations");
+      D.Report(PragmaTok.getLocation(), ID);
+    }
+
+    EnableAnnotate = true;
+  }
+};
+
 }
 
 static FrontendPluginRegistry::Add<AnnotateFunctionsAction>
 X("annotate-fns", "annotate functions");
+
+static PragmaHandlerRegistry::Add<PragmaAnnotateHandler>
+Y("enable_annotate","enable annotation");
diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
index d8e61713b3f..f7a9ea95182 100644
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -32,6 +32,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/TinyPtrVector.h"
 #include "llvm/Support/Allocator.h"
+#include "llvm/Support/Registry.h"
 #include <memory>
 #include <vector>
 
@@ -1937,6 +1938,9 @@ public:
   virtual bool HandleComment(Preprocessor &PP, SourceRange Comment) = 0;
 };
 
+/// \brief Registry of pragma handlers added by plugins
+typedef llvm::Registry<PragmaHandler> PragmaHandlerRegistry;
+
 }  // end namespace clang
 
 #endif
diff --git a/clang/lib/Lex/Pragma.cpp b/clang/lib/Lex/Pragma.cpp
index ff10acc6adc..1819f4f06bc 100644
--- a/clang/lib/Lex/Pragma.cpp
+++ b/clang/lib/Lex/Pragma.cpp
@@ -1490,6 +1490,13 @@ void Preprocessor::RegisterBuiltinPragmas() {
     AddPragmaHandler(new PragmaRegionHandler("region"));
     AddPragmaHandler(new PragmaRegionHandler("endregion"));
   }
+
+  // Pragmas added by plugins
+  for (PragmaHandlerRegistry::iterator it = PragmaHandlerRegistry::begin(),
+                                       ie = PragmaHandlerRegistry::end();
+       it != ie; ++it) {
+    AddPragmaHandler(it->instantiate().release());
+  }
 }
 
 /// Ignore all pragmas, useful for modes such as -Eonly which would otherwise
diff --git a/clang/test/Frontend/plugin-annotate-functions.c b/clang/test/Frontend/plugin-annotate-functions.c
index 1d7b79bf6ee..b8baf7ce77e 100644
--- a/clang/test/Frontend/plugin-annotate-functions.c
+++ b/clang/test/Frontend/plugin-annotate-functions.c
@@ -1,7 +1,25 @@
-// RUN: %clang -fplugin=%llvmshlibdir/AnnotateFunctions%pluginext -emit-llvm -S %s -o - | FileCheck %s
+// RUN: %clang -fplugin=%llvmshlibdir/AnnotateFunctions%pluginext -emit-llvm -DPRAGMA_ON -S %s -o - | FileCheck %s --check-prefix=PRAGMA
+// RUN: %clang -fplugin=%llvmshlibdir/AnnotateFunctions%pluginext -emit-llvm -S %s -o - | FileCheck %s --check-prefix=NOPRAGMA
+// RUN: not %clang -fplugin=%llvmshlibdir/AnnotateFunctions%pluginext -emit-llvm -DBAD_PRAGMA -S %s -o - 2>&1 | FileCheck %s --check-prefix=BADPRAGMA
 // REQUIRES: plugins, examples
 
-// CHECK: [[STR_VAR:@.+]] = private unnamed_addr constant [19 x i8] c"example_annotation\00"
-// CHECK: @llvm.global.annotations = {{.*}}@fn1{{.*}}[[STR_VAR]]{{.*}}@fn2{{.*}}[[STR_VAR]]
+#ifdef PRAGMA_ON
+#pragma enable_annotate
+#endif
+
+// BADPRAGMA: warning: extra tokens at end of #pragma directive
+#ifdef BAD_PRAGMA
+#pragma enable_annotate something
+#endif
+
+// PRAGMA: [[STR_VAR:@.+]] = private unnamed_addr constant [19 x i8] c"example_annotation\00"
+// PRAGMA: @llvm.global.annotations = {{.*}}@fn1{{.*}}[[STR_VAR]]{{.*}}@fn2{{.*}}[[STR_VAR]]
+// NOPRAGMA-NOT: [[STR_VAR:@.+]] = private unnamed_addr constant [19 x i8] c"example_annotation\00"
+// NOPRAGMA-NOT: @llvm.global.annotations = {{.*}}@fn1{{.*}}[[STR_VAR]]{{.*}}@fn2{{.*}}[[STR_VAR]]
 void fn1() { }
 void fn2() { }
+
+// BADPRAGMA: error: #pragma enable_annotate not allowed after declarations
+#ifdef BAD_PRAGMA
+#pragma enable_annotate
+#endif