[llvm-commits] [llvm] r137098 - /llvm/trunk/lib/Transforms/Utils/LowerInvoke.cpp

[Bill Wendling]

Author: void
Date: Mon Aug  8 20:09:21 2011
New Revision: 137098

URL: http://llvm.org/viewvc/llvm-project?rev=137098&view=rev
Log:
Remove an instance where the 'unwind' instruction was created.

The 'unwind' instruction was acting essentially as a placeholder, because it
would be replaced at the end of this function by a branch to the "unwind
handler". The 'unwind' instruction is going away, so use 'unreachable' instead,
which serves the same purpose as a placeholder.

Modified:
    llvm/trunk/lib/Transforms/Utils/LowerInvoke.cpp

Modified: llvm/trunk/lib/Transforms/Utils/LowerInvoke.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LowerInvoke.cpp?rev=137098&r1=137097&r2=137098&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LowerInvoke.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LowerInvoke.cpp Mon Aug  8 20:09:21 2011
@@ -406,6 +406,7 @@
   SmallVector<ReturnInst*,16> Returns;
   SmallVector<UnwindInst*,16> Unwinds;
   SmallVector<InvokeInst*,16> Invokes;
+  SmallVector<UnreachableInst*, 16> Unreachables;
 
   for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
     if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
@@ -486,9 +487,10 @@
 
     // Insert a load in the Catch block, and a switch on its value.  By default,
     // we go to a block that just does an unwind (which is the correct action
-    // for a standard call).
+    // for a standard call). We insert an unreachable instruction here and
+    // modify the block to jump to the correct unwinding pad later.
     BasicBlock *UnwindBB = BasicBlock::Create(F.getContext(), "unwindbb", &F);
-    Unwinds.push_back(new UnwindInst(F.getContext(), UnwindBB));
+    Unreachables.push_back(new UnreachableInst(F.getContext(), UnwindBB));
 
     Value *CatchLoad = new LoadInst(InvokeNum, "invoke.num", true, CatchBB);
     SwitchInst *CatchSwitch =
@@ -577,6 +579,12 @@
     Unwinds[i]->eraseFromParent();
   }
 
+  // Replace all inserted unreachables with a branch to the unwind handler.
+  for (unsigned i = 0, e = Unreachables.size(); i != e; ++i) {
+    BranchInst::Create(UnwindHandler, Unreachables[i]);
+    Unreachables[i]->eraseFromParent();
+  }
+
   // Finally, for any returns from this function, if this function contains an
   // invoke, restore the old jmpbuf pointer to its input value.
   if (OldJmpBufPtr) {