[LowerSwitch] Fixed faulty PHI node update

Summary:
When lowerswitch merge several cases into a new default block it's not
updating the PHI nodes accordingly. The code that update the PHI nodes
for the default edge only update the first entry and do not remove the
remaining ones, to make sure the number of entries match the number of
predecessors.

This is easily fixed by replacing the code that update the PHI node with
the already existing utility function for updating PHI nodes.

Reviewers: hans, reames, arsenm

Reviewed By: arsenm

Subscribers: wdng, llvm-commits

Differential Revision: https://reviews.llvm.org/D47055

llvm-svn: 332960

1 files changed, 9 insertions, 9 deletions

diff --git a/llvm/lib/Transforms/Utils/LowerSwitch.cpp b/llvm/lib/Transforms/Utils/LowerSwitch.cpp
index 441c5fd8b5a..76ad35832dc 100644
--- a/llvm/lib/Transforms/Utils/LowerSwitch.cpp
+++ b/llvm/lib/Transforms/Utils/LowerSwitch.cpp
@@ -512,25 +512,25 @@ void LowerSwitch::processSwitchInst(SwitchInst *SI,
     }
   }
 
+  unsigned NrOfDefaults = (SI->getDefaultDest() == Default) ? 1 : 0;
+  for (const auto &Case : SI->cases())
+    if (Case.getCaseSuccessor() == Default)
+      NrOfDefaults++;
+
   // Create a new, empty default block so that the new hierarchy of
   // if-then statements go to this and the PHI nodes are happy.
   BasicBlock *NewDefault = BasicBlock::Create(SI->getContext(), "NewDefault");
   F->getBasicBlockList().insert(Default->getIterator(), NewDefault);
   BranchInst::Create(Default, NewDefault);
 
-  // If there is an entry in any PHI nodes for the default edge, make sure
-  // to update them as well.
-  for (BasicBlock::iterator I = Default->begin(); isa<PHINode>(I); ++I) {
-    PHINode *PN = cast<PHINode>(I);
-    int BlockIdx = PN->getBasicBlockIndex(OrigBlock);
-    assert(BlockIdx != -1 && "Switch didn't go to this successor??");
-    PN->setIncomingBlock((unsigned)BlockIdx, NewDefault);
-  }
-
   BasicBlock *SwitchBlock =
       switchConvert(Cases.begin(), Cases.end(), LowerBound, UpperBound, Val,
                     OrigBlock, OrigBlock, NewDefault, UnreachableRanges);
 
+  // If there are entries in any PHI nodes for the default edge, make sure
+  // to update them as well.
+  fixPhis(Default, OrigBlock, NewDefault, NrOfDefaults);
+
   // Branch to our shiny new if-then stuff...
   BranchInst::Create(SwitchBlock, OrigBlock);