[clang][dataflow] Add a ControlFlowContext::build() overload taking a FunctionDecl.

This is the most common use case, so it makes sense to have a specific overload for it.

Reviewed By: xazax.hun

Differential Revision: https://reviews.llvm.org/D151183

Author: martinboehme

clang/include/clang/Analysis/FlowSensitive/ControlFlowContext.h

@@ -31,6 +31,11 @@ namespace dataflow {
 /// analysis.
 class ControlFlowContext {
 public:
+  /// Builds a ControlFlowContext from a `FunctionDecl`.
+  /// `Func.hasBody()` must be true, and `Func.isTemplated()` must be false.
+  static llvm::Expected<ControlFlowContext> build(const FunctionDecl &Func,
+                                                  ASTContext &C);
+
   /// Builds a ControlFlowContext from an AST node. `D` is the function in which
   /// `S` resides. `D.isTemplated()` must be false.
   static llvm::Expected<ControlFlowContext> build(const Decl &D, Stmt &S,

clang/lib/Analysis/FlowSensitive/ControlFlowContext.cpp

@@ -67,6 +67,16 @@ static llvm::BitVector findReachableBlocks(const CFG &Cfg) {
   return BlockReachable;
 }
 
+llvm::Expected<ControlFlowContext>
+ControlFlowContext::build(const FunctionDecl &Func, ASTContext &C) {
+  if (!Func.hasBody())
+    return llvm::createStringError(
+        std::make_error_code(std::errc::invalid_argument),
+        "Cannot analyze function without a body");
+
+  return build(Func, *Func.getBody(), C);
+}
+
 llvm::Expected<ControlFlowContext>
 ControlFlowContext::build(const Decl &D, Stmt &S, ASTContext &C) {
   if (D.isTemplated())

clang/lib/Analysis/FlowSensitive/DataflowAnalysisContext.cpp

@@ -210,8 +210,8 @@ DataflowAnalysisContext::getControlFlowContext(const FunctionDecl *F) {
   if (It != FunctionContexts.end())
     return &It->second;
 
-  if (Stmt *Body = F->getBody()) {
-    auto CFCtx = ControlFlowContext::build(*F, *Body, F->getASTContext());
+  if (F->hasBody()) {
+    auto CFCtx = ControlFlowContext::build(*F, F->getASTContext());
     // FIXME: Handle errors.
     assert(CFCtx);
     auto Result = FunctionContexts.insert({F, std::move(*CFCtx)});

clang/unittests/Analysis/FlowSensitive/TestingSupport.h

@@ -241,8 +241,7 @@ checkDataflow(AnalysisInputs<AnalysisT> AI,
           llvm::errc::invalid_argument, "Could not find the target function.");
 
     // Build the control flow graph for the target function.
-    auto MaybeCFCtx =
-        ControlFlowContext::build(*Target, *Target->getBody(), Context);
+    auto MaybeCFCtx = ControlFlowContext::build(*Target, Context);
     if (!MaybeCFCtx) return MaybeCFCtx.takeError();
     auto &CFCtx = *MaybeCFCtx;
 

clang/unittests/Analysis/FlowSensitive/TypeErasedDataflowAnalysisTest.cpp

@@ -67,8 +67,8 @@ runAnalysis(llvm::StringRef Code, AnalysisT (*MakeAnalysis)(ASTContext &)) {
   Stmt *Body = Func->getBody();
   assert(Body != nullptr);
 
-  auto CFCtx = llvm::cantFail(
-      ControlFlowContext::build(*Func, *Body, AST->getASTContext()));
+  auto CFCtx =
+      llvm::cantFail(ControlFlowContext::build(*Func, AST->getASTContext()));
 
   AnalysisT Analysis = MakeAnalysis(AST->getASTContext());
   DataflowAnalysisContext DACtx(std::make_unique<WatchedLiteralsSolver>());