Simplify EH control flow by observing that EH scopes form a simple

hierarchy of delegation, and that EH selector values are meaningful
function-wide (good thing, too, or inlining wouldn't work).
2,3d
1a
hierarchy of delegation and that EH selector values have the same
meaning everywhere in the function instead of being meaningful only
in the context of a specific selector.

This removes the need for routing edges through EH cleanups,
since a cleanup simply always branches to its enclosing scope.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@137293 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 23 insertions, 65 deletions

diff --git a/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h
index 42864ceb63..381842097f 100644
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -325,16 +325,8 @@ private:
   /// The innermost normal cleanup on the stack.
   stable_iterator InnermostNormalCleanup;
 
-  /// The innermost EH cleanup on the stack.
-  stable_iterator InnermostEHCleanup;
-
-  /// The number of catches on the stack.
-  unsigned CatchDepth;
-
-  /// The current EH destination index.  Reset to FirstCatchIndex
-  /// whenever the last EH cleanup is popped.
-  unsigned NextEHDestIndex;
-  enum { FirstEHDestIndex = 1 };
+  /// The innermost EH scope on the stack.
+  stable_iterator InnermostEHScope;
 
   /// The current set of branch fixups.  A branch fixup is a jump to
   /// an as-yet unemitted label, i.e. a label for which we don't yet
@@ -362,8 +354,7 @@ private:
 public:
   EHScopeStack() : StartOfBuffer(0), EndOfBuffer(0), StartOfData(0),
                    InnermostNormalCleanup(stable_end()),
-                   InnermostEHCleanup(stable_end()),
-                   CatchDepth(0), NextEHDestIndex(FirstEHDestIndex) {}
+                   InnermostEHScope(stable_end()) {}
   ~EHScopeStack() { delete[] StartOfBuffer; }
 
   // Variadic templates would make this not terrible.
@@ -435,8 +426,7 @@ public:
     return new (Buffer) T(N, a0, a1, a2);
   }
 
-  /// Pops a cleanup scope off the stack.  This should only be called
-  /// by CodeGenFunction::PopCleanupBlock.
+  /// Pops a cleanup scope off the stack.  This is private to CGCleanup.cpp.
   void popCleanup();
 
   /// Push a set of catch handlers on the stack.  The catch is
@@ -444,7 +434,7 @@ public:
   /// set on it.
   class EHCatchScope *pushCatch(unsigned NumHandlers);
 
-  /// Pops a catch scope off the stack.
+  /// Pops a catch scope off the stack.  This is private to CGException.cpp.
   void popCatch();
 
   /// Push an exceptions filter on the stack.
@@ -463,7 +453,7 @@ public:
   bool empty() const { return StartOfData == EndOfBuffer; }
 
   bool requiresLandingPad() const {
-    return (CatchDepth || hasEHCleanups());
+    return InnermostEHScope != stable_end();
   }
 
   /// Determines whether there are any normal cleanups on the stack.
@@ -476,19 +466,13 @@ public:
   stable_iterator getInnermostNormalCleanup() const {
     return InnermostNormalCleanup;
   }
-  stable_iterator getInnermostActiveNormalCleanup() const; // CGException.h
+  stable_iterator getInnermostActiveNormalCleanup() const;
 
-  /// Determines whether there are any EH cleanups on the stack.
-  bool hasEHCleanups() const {
-    return InnermostEHCleanup != stable_end();
+  stable_iterator getInnermostEHScope() const {
+    return InnermostEHScope;
   }
 
-  /// Returns the innermost EH cleanup on the stack, or stable_end()
-  /// if there are no EH cleanups.
-  stable_iterator getInnermostEHCleanup() const {
-    return InnermostEHCleanup;
-  }
-  stable_iterator getInnermostActiveEHCleanup() const; // CGException.h
+  stable_iterator getInnermostActiveEHScope() const;
 
   /// An unstable reference to a scope-stack depth.  Invalidated by
   /// pushes but not pops.
@@ -515,10 +499,6 @@ public:
   /// Translates an iterator into a stable_iterator.
   stable_iterator stabilize(iterator it) const;
 
-  /// Finds the nearest cleanup enclosing the given iterator.
-  /// Returns stable_iterator::invalid() if there are no such cleanups.
-  stable_iterator getEnclosingEHCleanup(iterator it) const;
-
   /// Turn a stable reference to a scope depth into a unstable pointer
   /// to the EH stack.
   iterator find(stable_iterator save) const;
@@ -547,9 +527,6 @@ public:
   /// Clears the branch-fixups list.  This should only be called by
   /// ResolveAllBranchFixups.
   void clearFixups() { BranchFixups.clear(); }
-
-  /// Gets the next EH destination index.
-  unsigned getNextEHDestIndex() { return NextEHDestIndex++; }
 };
 
 /// CodeGenFunction - This class organizes the per-function state that is used
@@ -580,26 +557,6 @@ public:
     unsigned Index;
   };
 
-  /// An unwind destination is an abstract label, branching to which
-  /// may require a jump out through EH cleanups.
-  struct UnwindDest {
-    UnwindDest() : Block(0), ScopeDepth(), Index(0) {}
-    UnwindDest(llvm::BasicBlock *Block,
-               EHScopeStack::stable_iterator Depth,
-               unsigned Index)
-      : Block(Block), ScopeDepth(Depth), Index(Index) {}
-
-    bool isValid() const { return Block != 0; }
-    llvm::BasicBlock *getBlock() const { return Block; }
-    EHScopeStack::stable_iterator getScopeDepth() const { return ScopeDepth; }
-    unsigned getDestIndex() const { return Index; }
-
-  private:
-    llvm::BasicBlock *Block;
-    EHScopeStack::stable_iterator ScopeDepth;
-    unsigned Index;
-  };
-
   CodeGenModule &CGM;  // Per-module state.
   const TargetInfo &Target;
 
@@ -629,9 +586,6 @@ public:
   /// iff the function has no return value.
   llvm::Value *ReturnValue;
 
-  /// RethrowBlock - Unified rethrow block.
-  UnwindDest RethrowBlock;
-
   /// AllocaInsertPoint - This is an instruction in the entry block before which
   /// we prefer to insert allocas.
   llvm::AssertingVH<llvm::Instruction> AllocaInsertPt;
@@ -652,10 +606,12 @@ public:
 
   /// i32s containing the indexes of the cleanup destinations.
   llvm::AllocaInst *NormalCleanupDest;
-  llvm::AllocaInst *EHCleanupDest;
 
   unsigned NextCleanupDestIndex;
 
+  /// EHResumeBlock - Unified block containing a call to llvm.eh.resume.
+  llvm::BasicBlock *EHResumeBlock;
+
   /// The exception slot.  All landing pads write the current
   /// exception pointer into this alloca.
   llvm::Value *ExceptionSlot;
@@ -886,14 +842,13 @@ public:
   /// a conservatively correct answer for this method.
   bool isObviouslyBranchWithoutCleanups(JumpDest Dest) const;
 
-  /// EmitBranchThroughEHCleanup - Emit a branch from the current
-  /// insert block through the EH cleanup handling code (if any) and
-  /// then on to \arg Dest.
-  void EmitBranchThroughEHCleanup(UnwindDest Dest);
+  /// popCatchScope - Pops the catch scope at the top of the EHScope
+  /// stack, emitting any required code (other than the catch handlers
+  /// themselves).
+  void popCatchScope();
 
-  /// getRethrowDest - Returns the unified outermost-scope rethrow
-  /// destination.
-  UnwindDest getRethrowDest();
+  llvm::BasicBlock *getEHResumeBlock();
+  llvm::BasicBlock *getEHDispatchBlock(EHScopeStack::stable_iterator scope);
 
   /// An object to manage conditionally-evaluated expressions.
   class ConditionalEvaluation {
@@ -1167,7 +1122,6 @@ public:
   llvm::Value *getEHSelectorSlot();
 
   llvm::Value *getNormalCleanupDestSlot();
-  llvm::Value *getEHCleanupDestSlot();
 
   llvm::BasicBlock *getUnreachableBlock() {
     if (!UnreachableBlock) {
@@ -1444,6 +1398,10 @@ public:
   /// means the block can be ignored if it is unreachable.
   void EmitBlock(llvm::BasicBlock *BB, bool IsFinished=false);
 
+  /// EmitBlockAfterUses - Emit the given block somewhere hopefully
+  /// near its uses, and leave the insertion point in it.
+  void EmitBlockAfterUses(llvm::BasicBlock *BB);
+
   /// EmitBranch - Emit a branch to the specified basic block from the current
   /// insert block, taking care to avoid creation of branches from dummy
   /// blocks. It is legal to call this function even if there is no current