Prune the unwind_to labels on BBs that don't need them. Another step in the

removal of invoke, PR1269.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48084 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 3 deletions

diff --git a/lib/Transforms/IPO/PruneEH.cpp b/lib/Transforms/IPO/PruneEH.cpp
index 4e621dc..fa8b95a 100644
--- a/lib/Transforms/IPO/PruneEH.cpp
+++ b/lib/Transforms/IPO/PruneEH.cpp
@@ -32,6 +32,7 @@ using namespace llvm;
 
 STATISTIC(NumRemoved, "Number of invokes removed");
 STATISTIC(NumUnreach, "Number of noreturn calls optimized");
+STATISTIC(NumBBUnwind, "Number of unwind_to removed from blocks");
 
 namespace {
   struct VISIBILITY_HIDDEN PruneEH : public CallGraphSCCPass {
@@ -153,6 +154,8 @@ bool PruneEH::runOnSCC(const std::vector<CallGraphNode *> &SCC) {
 bool PruneEH::SimplifyFunction(Function *F) {
   bool MadeChange = false;
   for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
+    bool couldUnwind = false;
+
     if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator()))
       if (II->doesNotThrow()) {
         SmallVector<Value*, 8> Args(II->op_begin()+3, II->op_end());
@@ -182,10 +185,11 @@ bool PruneEH::SimplifyFunction(Function *F) {
 
         ++NumRemoved;
         MadeChange = true;
-      }
+      } else
+        couldUnwind = true;
 
     for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; )
-      if (CallInst *CI = dyn_cast<CallInst>(I++))
+      if (CallInst *CI = dyn_cast<CallInst>(I++)) {
         if (CI->doesNotReturn() && !isa<UnreachableInst>(I)) {
           // This call calls a function that cannot return.  Insert an
           // unreachable instruction after it and simplify the code.  Do this
@@ -201,8 +205,17 @@ bool PruneEH::SimplifyFunction(Function *F) {
           MadeChange = true;
           ++NumUnreach;
           break;
-        }
+        } else if (!CI->doesNotThrow())
+          couldUnwind = true;
+      }
 
+    // Strip 'unwindTo' off of BBs that have no calls/invokes without nounwind.
+    if (!couldUnwind && BB->getUnwindDest()) {
+      MadeChange = true;
+      ++NumBBUnwind;
+      BB->getUnwindDest()->removePredecessor(BB, false, true);
+      BB->setUnwindDest(NULL);
+    }
   }
   return MadeChange;
 }