reapply my recent change that disables a piece of the switch formation

work, but fixes 400.perlbmk.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121749 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 13 insertions, 5 deletions

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index ca690e7f87..15e487c70c 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1515,7 +1515,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) {
       AddPredecessorToBlock(FalseDest, PredBlock, BB);
       PBI->setSuccessor(1, FalseDest);
     }
-    return SimplifyCFG(PBI->getParent()) | true;
+    return true;
   }
   return false;
 }
@@ -1905,17 +1905,25 @@ static bool SimplifyBranchOnICmpChain(BranchInst *BI, const TargetData *TD) {
   
   BasicBlock *BB = BI->getParent();
   
+  DEBUG(dbgs() << "CONVERTING 'icmp' CHAIN with " << Values.size()
+               << " cases into SWITCH.  BB is:\n" << *BB);
+  
   // If there are any extra values that couldn't be folded into the switch
   // then we evaluate them with an explicit branch first.  Split the block
   // right before the condbr to handle it.
   if (ExtraCase) {
-    return false;
+    DEBUG(dbgs() << "  ** 'icmp' chain unhandled condition: " << *ExtraCase
+                 << '\n');
     
     BasicBlock *NewBB = BB->splitBasicBlock(BI, "switch.early.test");
     // Remove the uncond branch added to the old block.
     TerminatorInst *OldTI = BB->getTerminator();
     
-    BranchInst::Create(EdgeBB, NewBB, ExtraCase, OldTI);
+    if (TrueWhenEqual)
+      BranchInst::Create(EdgeBB, NewBB, ExtraCase, OldTI);
+    else
+      BranchInst::Create(NewBB, EdgeBB, ExtraCase, OldTI);
+      
     OldTI->eraseFromParent();
     
     // If there are PHI nodes in EdgeBB, then we need to add a new entry to them
@@ -1955,6 +1963,7 @@ static bool SimplifyBranchOnICmpChain(BranchInst *BI, const TargetData *TD) {
   
   // Erase the old branch instruction.
   EraseTerminatorInstAndDCECond(BI);
+  
   return true;
 }
 
@@ -2410,8 +2419,7 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
     if (BI->isUnconditional()) {
       if (SimplifyUncondBranch(BI)) return true;
     } else {
-      if (SimplifyCondBranch(BI))
-        return true;
+      if (SimplifyCondBranch(BI)) return true;
     }
   } else if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
     if (SimplifyReturn(RI)) return true;