Do not perform the analysis based warning if the warnings are ignored

This saves some cycles when compiling with "-w".

(Also fix a potential crash on invalid code for tools that tries to recover from some
errors, because analysis might compute the CFG which crashes if the code contains
invalid declaration. This does not happen normally with because we also don't perform
these analysis if there was an error.)

Differential Revision: https://reviews.llvm.org/D40242

llvm-svn: 318900

clang/lib/Sema/AnalysisBasedWarnings.cpp

@@ -2080,10 +2080,10 @@ AnalysisBasedWarnings::IssueWarnings(sema::AnalysisBasedWarnings::Policy P,
   //     time.
   DiagnosticsEngine &Diags = S.getDiagnostics();
 
-  // Do not do any analysis for declarations in system headers if we are
-  // going to just ignore them.
-  if (Diags.getSuppressSystemWarnings() &&
-      S.SourceMgr.isInSystemHeader(D->getLocation()))
+  // Do not do any analysis if we are going to just ignore them.
+  if (Diags.getIgnoreAllWarnings() ||
+      (Diags.getSuppressSystemWarnings() &&
+       S.SourceMgr.isInSystemHeader(D->getLocation())))
     return;
 
   // For code in dependent contexts, we'll do this at instantiation time.

clang/unittests/Tooling/ToolingTest.cpp

@@ -564,5 +564,31 @@ TEST(ClangToolTest, InjectDiagnosticConsumerInBuildASTs) {
 }
 #endif
 
+TEST(runToolOnCode, TestResetDiagnostics) {
+  // This is a tool that resets the diagnostic during the compilation.
+  struct ResetDiagnosticAction : public clang::ASTFrontendAction {
+    std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &Compiler,
+                                                   StringRef) override {
+      struct Consumer : public clang::ASTConsumer {
+        bool HandleTopLevelDecl(clang::DeclGroupRef D) override {
+          auto &Diags = (*D.begin())->getASTContext().getDiagnostics();
+          // Ignore any error
+          Diags.Reset();
+          // Disable warnings because computing the CFG might crash.
+          Diags.setIgnoreAllWarnings(true);
+          return true;
+        }
+      };
+      return llvm::make_unique<Consumer>();
+    }
+  };
+
+  // Should not crash
+  EXPECT_FALSE(
+      runToolOnCode(new ResetDiagnosticAction,
+                    "struct Foo { Foo(int); ~Foo(); struct Fwd _fwd; };"
+                    "void func() { long x; Foo f(x); }"));
+}
+
 } // end namespace tooling
 } // end namespace clang