Fix PR255: [tailduplication] Single basic block loops are very rare

Note that this is a band-aid put over a band-aid.  This just undisables
tail duplication in on very specific case that it seems to work in.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11989 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/TailDuplication.cpp b/lib/Transforms/Scalar/TailDuplication.cpp
index 7d5aac4fe73394f3b601f82d51fa1a40b36ea512..315b90697cf5202eecb3c443d65768cbc4a57050 100644 (file)
--- a/lib/Transforms/Scalar/TailDuplication.cpp
+++ b/lib/Transforms/Scalar/TailDuplication.cpp
@@ -125,6 +125,7 @@ bool TailDup::shouldEliminateUnconditionalBranch(TerminatorInst *TI) {
 bool TailDup::canEliminateUnconditionalBranch(TerminatorInst *TI) {
   // Basically, we refuse to make the transformation if any of the values
   // computed in the 'tail' are used in any other basic blocks.
+  BasicBlock *BB = TI->getParent();
   BasicBlock *Tail = TI->getSuccessor(0);
   assert(isa<BranchInst>(TI) && cast<BranchInst>(TI)->isUnconditional());
   
@@ -132,7 +133,7 @@ bool TailDup::canEliminateUnconditionalBranch(TerminatorInst *TI) {
     for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
          ++UI) {
       Instruction *User = cast<Instruction>(*UI);
-      if (User->getParent() != Tail || isa<PHINode>(User))
+      if (User->getParent() != Tail && User->getParent() != BB)
         return false;
     }
   return true;