Early exit if we don't have invokes. The 'Unwinds' vector isn't modified unless

we have invokes, so there is no functionality change here.

llvm-svn: 122990

llvm/lib/CodeGen/SjLjEHPrepare.cpp

@@ -319,8 +319,12 @@ bool SjLjEHPass::insertSjLjEHSupport(Function &F) {
       Unwinds.push_back(UI);
     }
   }
-  // If we don't have any invokes or unwinds, there's nothing to do.
+
-  if (Unwinds.empty() && Invokes.empty()) return false;
+  NumInvokes += Invokes.size();
+  NumUnwinds += Unwinds.size();
+
+  // If we don't have any invokes, there's nothing to do.
+  if (Invokes.empty()) return false;
 
   // Find the eh.selector.*, eh.exception and alloca calls.
   //
@@ -334,6 +338,7 @@ bool SjLjEHPass::insertSjLjEHSupport(Function &F) {
   SmallVector<CallInst*,16> EH_Selectors;
   SmallVector<CallInst*,16> EH_Exceptions;
   SmallVector<Instruction*,16> JmpbufUpdatePoints;
+
   // Note: Skip the entry block since there's nothing there that interests
   // us. eh.selector and eh.exception shouldn't ever be there, and we
   // want to disregard any allocas that are there.
@@ -353,22 +358,19 @@ bool SjLjEHPass::insertSjLjEHSupport(Function &F) {
       }
     }
   }
+
   // If we don't have any eh.selector calls, we can't determine the personality
   // function. Without a personality function, we can't process exceptions.
   if (!PersonalityFn) return false;
 
-  NumInvokes += Invokes.size();
+  // We have invokes, so we need to add register/unregister calls to get this
-  NumUnwinds += Unwinds.size();
+  // function onto the global unwind stack.
-
-  if (!Invokes.empty()) {
-    // We have invokes, so we need to add register/unregister calls to get
-    // this function onto the global unwind stack.
   //
   // First thing we need to do is scan the whole function for values that are
-    // live across unwind edges.  Each value that is live across an unwind edge
+  // live across unwind edges.  Each value that is live across an unwind edge we
-    // we spill into a stack location, guaranteeing that there is nothing live
+  // spill into a stack location, guaranteeing that there is nothing live across
-    // across the unwind edge.  This process also splits all critical edges
+  // the unwind edge.  This process also splits all critical edges coming out of
-    // coming out of invoke's.
+  // invoke's.
   splitLiveRangesAcrossInvokes(Invokes);
 
   BasicBlock *EntryBB = F.begin();
@@ -405,22 +407,22 @@ bool SjLjEHPass::insertSjLjEHSupport(Function &F) {
                                                    "exception_gep",
                                                    EntryBB->getTerminator());
 
-    // The result of the eh.selector call will be replaced with a
+  // The result of the eh.selector call will be replaced with a a reference to
-    // a reference to the selector value returned in the function
+  // the selector value returned in the function context. We leave the selector
-    // context. We leave the selector itself so the EH analysis later
+  // itself so the EH analysis later can use it.
-    // can use it.
   for (int i = 0, e = EH_Selectors.size(); i < e; ++i) {
     CallInst *I = EH_Selectors[i];
     Value *SelectorVal = new LoadInst(SelectorAddr, "select_val", true, I);
     I->replaceAllUsesWith(SelectorVal);
   }
-    // eh.exception calls are replaced with references to the proper
+
-    // location in the context. Unlike eh.selector, the eh.exception
+  // eh.exception calls are replaced with references to the proper location in
-    // calls are removed entirely.
+  // the context. Unlike eh.selector, the eh.exception calls are removed
+  // entirely.
   for (int i = 0, e = EH_Exceptions.size(); i < e; ++i) {
     CallInst *I = EH_Exceptions[i];
-      // Possible for there to be duplicates, so check to make sure
+    // Possible for there to be duplicates, so check to make sure the
-      // the instruction hasn't already been removed.
+    // instruction hasn't already been removed.
     if (!I->getParent()) continue;
     Value *Val = new LoadInst(ExceptionAddr, "exception", true, I);
     const Type *Ty = Type::getInt8PtrTy(F.getContext());
@@ -432,25 +434,25 @@ bool SjLjEHPass::insertSjLjEHSupport(Function &F) {
 
   // The entry block changes to have the eh.sjlj.setjmp, with a conditional
   // branch to a dispatch block for non-zero returns. If we return normally,
-    // we're not handling an exception and just register the function context
+  // we're not handling an exception and just register the function context and
-    // and continue.
+  // continue.
 
   // Create the dispatch block.  The dispatch block is basically a big switch
   // statement that goes to all of the invoke landing pads.
   BasicBlock *DispatchBlock =
     BasicBlock::Create(F.getContext(), "eh.sjlj.setjmp.catch", &F);
 
-    // Add a call to dispatch_setup at the start of the dispatch block. This
+  // Add a call to dispatch_setup at the start of the dispatch block. This is
-    // is expanded to any target-specific setup that needs to be done.
+  // expanded to any target-specific setup that needs to be done.
   Value *SetupArg =
     CastInst::Create(Instruction::BitCast, FunctionContext,
                      Type::getInt8PtrTy(F.getContext()), "",
                      DispatchBlock);
   CallInst::Create(DispatchSetupFn, SetupArg, "", DispatchBlock);
 
-    // Insert a load of the callsite in the dispatch block, and a switch on
+  // Insert a load of the callsite in the dispatch block, and a switch on its
-    // its value.  By default, we go to a block that just does an unwind
+  // value.  By default, we go to a block that just does an unwind (which is the
-    // (which is the correct action for a standard call).
+  // correct action for a standard call).
   BasicBlock *UnwindBlock =
     BasicBlock::Create(F.getContext(), "unwindbb", &F);
   Unwinds.push_back(new UnwindInst(F.getContext(), UnwindBlock));
@@ -538,17 +540,16 @@ bool SjLjEHPass::insertSjLjEHSupport(Function &F) {
                      ContBlock->getTerminator());
   Register->setDoesNotThrow();
 
-    // At this point, we are all set up, update the invoke instructions
+  // At this point, we are all set up, update the invoke instructions to mark
-    // to mark their call_site values, and fill in the dispatch switch
+  // their call_site values, and fill in the dispatch switch accordingly.
-    // accordingly.
   for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
     markInvokeCallSite(Invokes[i], i+1, CallSite, DispatchSwitch);
 
-    // Mark call instructions that aren't nounwind as no-action
+  // Mark call instructions that aren't nounwind as no-action (call_site ==
-    // (call_site == -1). Skip the entry block, as prior to then, no function
+  // -1). Skip the entry block, as prior to then, no function context has been
-    // context has been created for this function and any unexpected exceptions
+  // created for this function and any unexpected exceptions thrown will go
-    // thrown will go directly to the caller's context, which is what we want
+  // directly to the caller's context, which is what we want anyway, so no need
-    // anyway, so no need to do anything here.
+  // to do anything here.
   for (Function::iterator BB = F.begin(), E = F.end(); ++BB != E;) {
     for (BasicBlock::iterator I = BB->begin(), end = BB->end(); I != end; ++I)
       if (CallInst *CI = dyn_cast<CallInst>(I)) {
@@ -567,8 +568,8 @@ bool SjLjEHPass::insertSjLjEHSupport(Function &F) {
     Unwinds[i]->eraseFromParent();
   }
 
-    // Following any allocas not in the entry block, update the saved SP
+  // Following any allocas not in the entry block, update the saved SP in the
-    // in the jmpbuf to the new value.
+  // jmpbuf to the new value.
   for (unsigned i = 0, e = JmpbufUpdatePoints.size(); i != e; ++i) {
     Instruction *AI = JmpbufUpdatePoints[i];
     Instruction *StackAddr = CallInst::Create(StackAddrFn, "sp");
@@ -581,7 +582,6 @@ bool SjLjEHPass::insertSjLjEHSupport(Function &F) {
   // invoke, add a call to unregister the function context.
   for (unsigned i = 0, e = Returns.size(); i != e; ++i)
     CallInst::Create(UnregisterFn, FunctionContext, "", Returns[i]);
-  }
 
   return true;
 }