Also optimize large switch statements.

The isValueEqualityComparison() guard at the top of SimplifySwitch()
only applies to some of the possible transformations.

The newer transformations work just fine on large switches, and the
check on predecessor count is nonsensical.

llvm-svn: 166710

1 files changed, 20 insertions, 22 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 870e2b2adeb..427ac4ed143 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -3583,32 +3583,30 @@ static bool SwitchToLookupTable(SwitchInst *SI,
 }
 
 bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder) {
-  // If this switch is too complex to want to look at, ignore it.
-  if (!isValueEqualityComparison(SI))
-    return false;
-
   BasicBlock *BB = SI->getParent();
 
-  // If we only have one predecessor, and if it is a branch on this value,
-  // see if that predecessor totally determines the outcome of this switch.
-  if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
-    if (SimplifyEqualityComparisonWithOnlyPredecessor(SI, OnlyPred, Builder))
-      return SimplifyCFG(BB) | true;
+  if (isValueEqualityComparison(SI)) {
+    // If we only have one predecessor, and if it is a branch on this value,
+    // see if that predecessor totally determines the outcome of this switch.
+    if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
+      if (SimplifyEqualityComparisonWithOnlyPredecessor(SI, OnlyPred, Builder))
+        return SimplifyCFG(BB) | true;
 
-  Value *Cond = SI->getCondition();
-  if (SelectInst *Select = dyn_cast<SelectInst>(Cond))
-    if (SimplifySwitchOnSelect(SI, Select))
-      return SimplifyCFG(BB) | true;
+    Value *Cond = SI->getCondition();
+    if (SelectInst *Select = dyn_cast<SelectInst>(Cond))
+      if (SimplifySwitchOnSelect(SI, Select))
+        return SimplifyCFG(BB) | true;
 
-  // If the block only contains the switch, see if we can fold the block
-  // away into any preds.
-  BasicBlock::iterator BBI = BB->begin();
-  // Ignore dbg intrinsics.
-  while (isa<DbgInfoIntrinsic>(BBI))
-    ++BBI;
-  if (SI == &*BBI)
-    if (FoldValueComparisonIntoPredecessors(SI, Builder))
-      return SimplifyCFG(BB) | true;
+    // If the block only contains the switch, see if we can fold the block
+    // away into any preds.
+    BasicBlock::iterator BBI = BB->begin();
+    // Ignore dbg intrinsics.
+    while (isa<DbgInfoIntrinsic>(BBI))
+      ++BBI;
+    if (SI == &*BBI)
+      if (FoldValueComparisonIntoPredecessors(SI, Builder))
+        return SimplifyCFG(BB) | true;
+  }
 
   // Try to transform the switch into an icmp and a branch.
   if (TurnSwitchRangeIntoICmp(SI, Builder))