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-rw-r--r--llvm/lib/Transforms/Utils/SimplifyCFG.cpp168
1 files changed, 91 insertions, 77 deletions
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 23dd2650f97..4e58e492b93 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1847,6 +1847,93 @@ static bool TryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI) {
return true;
}
+/// SimplifyBranchOnICmpChain - The specified branch is a conditional branch.
+/// Check to see if it is branching on an or/and chain of icmp instructions, and
+/// fold it into a switch instruction if so.
+static bool SimplifyBranchOnICmpChain(BranchInst *BI, const TargetData *TD) {
+ Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
+ if (Cond == 0) return false;
+
+
+ // Change br (X == 0 | X == 1), T, F into a switch instruction.
+ // If this is a bunch of seteq's or'd together, or if it's a bunch of
+ // 'setne's and'ed together, collect them.
+ Value *CompVal = 0;
+ std::vector<ConstantInt*> Values;
+ bool TrueWhenEqual = true;
+ Value *ExtraCase = 0;
+
+ if (Cond->getOpcode() == Instruction::Or) {
+ CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, true);
+ } else if (Cond->getOpcode() == Instruction::And) {
+ CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, false);
+ TrueWhenEqual = false;
+ }
+
+ // If we didn't have a multiply compared value, fail.
+ if (CompVal == 0) return false;
+
+ // There might be duplicate constants in the list, which the switch
+ // instruction can't handle, remove them now.
+ array_pod_sort(Values.begin(), Values.end(), ConstantIntSortPredicate);
+ Values.erase(std::unique(Values.begin(), Values.end()), Values.end());
+
+ // If Extra was used, we require at least two switch values to do the
+ // transformation. A switch with one value is just an cond branch.
+ if (ExtraCase && Values.size() < 2) return false;
+
+ // Figure out which block is which destination.
+ BasicBlock *DefaultBB = BI->getSuccessor(1);
+ BasicBlock *EdgeBB = BI->getSuccessor(0);
+ if (!TrueWhenEqual) std::swap(DefaultBB, EdgeBB);
+
+ BasicBlock *BB = BI->getParent();
+
+ // 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) {
+ 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);
+ OldTI->eraseFromParent();
+ BB = NewBB;
+ }
+
+ // Convert pointer to int before we switch.
+ if (CompVal->getType()->isPointerTy()) {
+ assert(TD && "Cannot switch on pointer without TargetData");
+ CompVal = new PtrToIntInst(CompVal,
+ TD->getIntPtrType(CompVal->getContext()),
+ "magicptr", BI);
+ }
+
+ // Create the new switch instruction now.
+ SwitchInst *New =
+ SwitchInst::Create(CompVal, DefaultBB, Values.size(), BI);
+
+ // Add all of the 'cases' to the switch instruction.
+ for (unsigned i = 0, e = Values.size(); i != e; ++i)
+ New->addCase(Values[i], EdgeBB);
+
+ // We added edges from PI to the EdgeBB. As such, if there were any
+ // PHI nodes in EdgeBB, they need entries to be added corresponding to
+ // the number of edges added.
+ for (BasicBlock::iterator BBI = EdgeBB->begin();
+ isa<PHINode>(BBI); ++BBI) {
+ PHINode *PN = cast<PHINode>(BBI);
+ Value *InVal = PN->getIncomingValueForBlock(BB);
+ for (unsigned i = 0, e = Values.size()-1; i != e; ++i)
+ PN->addIncoming(InVal, BB);
+ }
+
+ // Erase the old branch instruction.
+ EraseTerminatorInstAndDCECond(BI);
+ return true;
+}
+
bool SimplifyCFGOpt::run(BasicBlock *BB) {
bool Changed = false;
Function *Fn = BB->getParent();
@@ -2047,6 +2134,10 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
}
}
+ // Try to turn "br (X == 0 | X == 1), T, F" into a switch instruction.
+ if (SimplifyBranchOnICmpChain(BI, TD))
+ return true;
+
// If this is a branch on a phi node in the current block, thread control
// through this block if any PHI node entries are constants.
if (PHINode *PN = dyn_cast<PHINode>(BI->getCondition()))
@@ -2060,89 +2151,12 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
if (FoldBranchToCommonDest(BI))
return SimplifyCFG(BB) | true;
-
// Scan predecessor blocks for conditional branches.
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
if (BranchInst *PBI = dyn_cast<BranchInst>((*PI)->getTerminator()))
if (PBI != BI && PBI->isConditional())
if (SimplifyCondBranchToCondBranch(PBI, BI))
return SimplifyCFG(BB) | true;
-
-
- // Change br (X == 0 | X == 1), T, F into a switch instruction.
- // If this is a bunch of seteq's or'd together, or if it's a bunch of
- // 'setne's and'ed together, collect them.
- Value *CompVal = 0;
- std::vector<ConstantInt*> Values;
- bool TrueWhenEqual = true;
- Value *ExtraCase = 0;
-
- if (Instruction *Cond = dyn_cast<Instruction>(BI->getCondition())) {
- if (Cond->getOpcode() == Instruction::Or) {
- CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, true);
- } else if (Cond->getOpcode() == Instruction::And) {
- CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, false);
- TrueWhenEqual = false;
- }
- }
-
- // We do this transformation if we'll end up creating a switch with at
- // least two values if Extra is used.
- if (CompVal && (!ExtraCase || Values.size() > 1)) {
- // There might be duplicate constants in the list, which the switch
- // instruction can't handle, remove them now.
- array_pod_sort(Values.begin(), Values.end(), ConstantIntSortPredicate);
- Values.erase(std::unique(Values.begin(), Values.end()), Values.end());
-
- // Figure out which block is which destination.
- BasicBlock *DefaultBB = BI->getSuccessor(1);
- BasicBlock *EdgeBB = BI->getSuccessor(0);
- if (!TrueWhenEqual) std::swap(DefaultBB, EdgeBB);
-
- // 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) {
- 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);
- OldTI->eraseFromParent();
- BB = NewBB;
- }
-
- // Convert pointer to int before we switch.
- if (CompVal->getType()->isPointerTy()) {
- assert(TD && "Cannot switch on pointer without TargetData");
- CompVal = new PtrToIntInst(CompVal,
- TD->getIntPtrType(CompVal->getContext()),
- "magicptr", BI);
- }
-
- // Create the new switch instruction now.
- SwitchInst *New =
- SwitchInst::Create(CompVal, DefaultBB, Values.size(), BI);
-
- // Add all of the 'cases' to the switch instruction.
- for (unsigned i = 0, e = Values.size(); i != e; ++i)
- New->addCase(Values[i], EdgeBB);
-
- // We added edges from PI to the EdgeBB. As such, if there were any
- // PHI nodes in EdgeBB, they need entries to be added corresponding to
- // the number of edges added.
- for (BasicBlock::iterator BBI = EdgeBB->begin();
- isa<PHINode>(BBI); ++BBI) {
- PHINode *PN = cast<PHINode>(BBI);
- Value *InVal = PN->getIncomingValueForBlock(BB);
- for (unsigned i = 0, e = Values.size()-1; i != e; ++i)
- PN->addIncoming(InVal, BB);
- }
-
- // Erase the old branch instruction.
- EraseTerminatorInstAndDCECond(BI);
- return true;
- }
}
} else if (isa<UnreachableInst>(BB->getTerminator())) {
// If there are any instructions immediately before the unreachable that can
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