Emit @finally blocks completely lazily instead of forcing their

existence by always threading an edge from the catchall.  Not doing
this was previously causing a crash in the very extreme case where
neither the normal cleanup nor the EH catchall was actually reachable:
we would delete the catchall entry block, which would cause us to
delete the entry block of the finally cleanup as well because the
cleanup logic would merge the blocks, which in turn triggered an assert
because later blocks in the finally would still be using values from the
entry.  Laziness turns out to be the most elegant solution to the problem.

llvm-svn: 133601

1 files changed, 21 insertions, 9 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index e72d6ce..1aaa700 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -635,16 +635,28 @@ public:
   /// rethrows.
   llvm::SmallVector<llvm::Value*, 8> ObjCEHValueStack;
 
-  // A struct holding information about a finally block's IR
-  // generation.  For now, doesn't actually hold anything.
-  struct FinallyInfo {
-  };
+  /// A class controlling the emission of a finally block.
+  class FinallyInfo {
+    /// Where the catchall's edge through the cleanup should go.
+    JumpDest RethrowDest;
+
+    /// A function to call to enter the catch.
+    llvm::Constant *BeginCatchFn;
+
+    /// An i1 variable indicating whether or not the @finally is
+    /// running for an exception.
+    llvm::AllocaInst *ForEHVar;
 
-  FinallyInfo EnterFinallyBlock(const Stmt *Stmt,
-                                llvm::Constant *BeginCatchFn,
-                                llvm::Constant *EndCatchFn,
-                                llvm::Constant *RethrowFn);
-  void ExitFinallyBlock(FinallyInfo &FinallyInfo);
+    /// An i8* variable into which the exception pointer to rethrow
+    /// has been saved.
+    llvm::AllocaInst *SavedExnVar;
+
+  public:
+    void enter(CodeGenFunction &CGF, const Stmt *Finally,
+               llvm::Constant *beginCatchFn, llvm::Constant *endCatchFn,
+               llvm::Constant *rethrowFn);
+    void exit(CodeGenFunction &CGF);
+  };
 
   /// pushFullExprCleanup - Push a cleanup to be run at the end of the
   /// current full-expression.  Safe against the possibility that