Implement SimplifyCFG/2003-08-17-FoldSwitch.ll:test5

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@8093 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 13 insertions, 0 deletions

diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index e668dc3d4a..52973f8724 100644
--- a/lib/Transforms/Utils/Local.cpp
+++ b/lib/Transforms/Utils/Local.cpp
@@ -80,6 +80,9 @@ bool ConstantFoldTerminator(BasicBlock *BB) {
     // single branch instruction!
     ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition());
     BasicBlock *TheOnlyDest = SI->getSuccessor(0);  // The default dest
+    BasicBlock *DefaultDest = TheOnlyDest;
+    assert(TheOnlyDest == SI->getDefaultDest() &&
+           "Default destination is not successor #0?");
 
     // Figure out which case it goes to...
     for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) {
@@ -89,6 +92,16 @@ bool ConstantFoldTerminator(BasicBlock *BB) {
         break;
       }
 
+      // Check to see if this branch is going to the same place as the default
+      // dest.  If so, eliminate it as an explicit compare.
+      if (SI->getSuccessor(i) == DefaultDest) {
+        // Remove this entry...
+        DefaultDest->removePredecessor(SI->getParent());
+        SI->removeCase(i);
+        --i; --e;  // Don't skip an entry...
+        continue;
+      }
+
       // Otherwise, check to see if the switch only branches to one destination.
       // We do this by reseting "TheOnlyDest" to null when we find two non-equal
       // destinations.