X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FWinEHPrepare.cpp;h=0d26ed333ca7134928023f870ce50082299c389f;hb=81474d36a0e7415f765193f5df272522930831a8;hp=0f84ba0a7234c6455f01061dae427dec59c7cb8b;hpb=4fe74caa61ff0a7b08c98a070fd1e4b85d4d9b7f;p=oota-llvm.git

diff --git a/lib/CodeGen/WinEHPrepare.cpp b/lib/CodeGen/WinEHPrepare.cpp
index 0f84ba0a723..0d26ed333ca 100644
--- a/lib/CodeGen/WinEHPrepare.cpp
+++ b/lib/CodeGen/WinEHPrepare.cpp
@@ -533,9 +533,9 @@ void WinEHPrepare::findSEHEHReturnPoints(
     BasicBlock *NextBB;
     Constant *Selector;
     if (isSelectorDispatch(BB, CatchHandler, Selector, NextBB)) {
-      // Split the edge if there is a phi node. Returning from EH to a phi node
-      // is just as impossible as having a phi after an indirectbr.
-      if (isa<PHINode>(CatchHandler->begin())) {
+      // Split the edge if there are multiple predecessors. This creates a place
+      // where we can insert EH recovery code.
+      if (!CatchHandler->getSinglePredecessor()) {
         DEBUG(dbgs() << "splitting EH return edge from " << BB->getName()
                      << " to " << CatchHandler->getName() << '\n');
         BBI = CatchHandler = SplitCriticalEdge(
@@ -616,6 +616,26 @@ void WinEHPrepare::demoteValuesLiveAcrossHandlers(
   // identifyEHBlocks() should have been called before this function.
   assert(!NormalBlocks.empty());
 
+  // Try to avoid demoting EH pointer and selector values. They get in the way
+  // of our pattern matching.
+  SmallPtrSet<Instruction *, 10> EHVals;
+  for (BasicBlock &BB : F) {
+    LandingPadInst *LP = BB.getLandingPadInst();
+    if (!LP)
+      continue;
+    EHVals.insert(LP);
+    for (User *U : LP->users()) {
+      auto *EI = dyn_cast<ExtractValueInst>(U);
+      if (!EI)
+        continue;
+      EHVals.insert(EI);
+      for (User *U2 : EI->users()) {
+        if (auto *PN = dyn_cast<PHINode>(U2))
+          EHVals.insert(PN);
+      }
+    }
+  }
+
   SetVector<Argument *> ArgsToDemote;
   SetVector<Instruction *> InstrsToDemote;
   for (BasicBlock &BB : F) {
@@ -641,7 +661,11 @@ void WinEHPrepare::demoteValuesLiveAcrossHandlers(
           continue;
         }
 
+        // Don't demote EH values.
         auto *OpI = cast<Instruction>(Op);
+        if (EHVals.count(OpI))
+          continue;
+
         BasicBlock *OpBB = OpI->getParent();
         // If a value is produced and consumed in the same BB, we don't need to
         // demote it.
@@ -822,7 +846,8 @@ bool WinEHPrepare::prepareExceptionHandlers(
     LPad->replaceAllUsesWith(UndefValue::get(LPad->getType()));
 
     // Rewrite uses of the exception pointer to loads of an alloca.
-    for (Instruction *E : SEHCodeUses) {
+    while (!SEHCodeUses.empty()) {
+      Instruction *E = SEHCodeUses.pop_back_val();
       SmallVector<Use *, 4> Uses;
       for (Use &U : E->uses())
         Uses.push_back(&U);
@@ -830,13 +855,10 @@ bool WinEHPrepare::prepareExceptionHandlers(
         auto *I = cast<Instruction>(U->getUser());
         if (isa<ResumeInst>(I))
           continue;
-        LoadInst *LI;
         if (auto *Phi = dyn_cast<PHINode>(I))
-          LI = new LoadInst(SEHExceptionCodeSlot, "sehcode", false,
-                            Phi->getIncomingBlock(*U)->getTerminator());
+          SEHCodeUses.push_back(Phi);
         else
-          LI = new LoadInst(SEHExceptionCodeSlot, "sehcode", false, I);
-        U->set(LI);
+          U->set(new LoadInst(SEHExceptionCodeSlot, "sehcode", false, I));
       }
       E->replaceAllUsesWith(UndefValue::get(E->getType()));
       E->eraseFromParent();