Fix 12513: Loop unrolling breaks with indirect branches.
Take this opportunity to generalize the indirectbr bailout logic for
loop transformations. CFG transformations will never get indirectbr
right, and there's no point trying.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154386 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/LoopUnswitch.cpp b/lib/Transforms/Scalar/LoopUnswitch.cpp
index 1c93a70..ee23268 100644
--- a/lib/Transforms/Scalar/LoopUnswitch.cpp
+++ b/lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -192,10 +192,6 @@
loopPreheader = currentLoop->getLoopPreheader();
}
- /// HasIndirectBrsInPreds - Returns true if there are predecessors, that are
- /// terminated with indirect branch instruction.
- bool HasIndirectBrsInPreds(const SmallVectorImpl<BasicBlock *> &ExitBlocks);
-
/// Split all of the edges from inside the loop to their exit blocks.
/// Update the appropriate Phi nodes as we do so.
void SplitExitEdges(Loop *L, const SmallVector<BasicBlock *, 8> &ExitBlocks);
@@ -203,7 +199,7 @@
bool UnswitchIfProfitable(Value *LoopCond, Constant *Val);
void UnswitchTrivialCondition(Loop *L, Value *Cond, Constant *Val,
BasicBlock *ExitBlock);
- bool UnswitchNontrivialCondition(Value *LIC, Constant *OnVal, Loop *L);
+ void UnswitchNontrivialCondition(Value *LIC, Constant *OnVal, Loop *L);
void RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC,
Constant *Val, bool isEqual);
@@ -409,6 +405,14 @@
if (!loopPreheader)
return false;
+ // Loops with indirectbr cannot be cloned.
+ if (!currentLoop->isSafeToClone())
+ return false;
+
+ // Without dedicated exits, splitting the exit edge may fail.
+ if (!currentLoop->hasDedicatedExits())
+ return false;
+
LLVMContext &Context = loopHeader->getContext();
// Probably we reach the quota of branches for this loop. If so
@@ -638,7 +642,8 @@
if (OptimizeForSize || F->hasFnAttr(Attribute::OptimizeForSize))
return false;
- return UnswitchNontrivialCondition(LoopCond, Val, currentLoop);
+ UnswitchNontrivialCondition(LoopCond, Val, currentLoop);
+ return true;
}
/// CloneLoop - Recursively clone the specified loop and all of its children,
@@ -733,24 +738,6 @@
++NumTrivial;
}
-/// HasIndirectBrsInPreds - Returns true if there are predecessors, that are
-/// terminated with indirect branch instruction.
-bool LoopUnswitch::HasIndirectBrsInPreds(
- const SmallVectorImpl<BasicBlock *> &ExitBlocks){
-
- for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
- const BasicBlock *ExitBlock = ExitBlocks[i];
- for (const_pred_iterator p = pred_begin(ExitBlock), e = pred_end(ExitBlock);
- p != e; ++p) {
- // Cannot split an edge from an IndirectBrInst
- if (isa<IndirectBrInst>((*p)->getTerminator()))
- return true;
-
- }
- }
- return false;
-}
-
/// SplitExitEdges - Split all of the edges from inside the loop to their exit
/// blocks. Update the appropriate Phi nodes as we do so.
void LoopUnswitch::SplitExitEdges(Loop *L,
@@ -776,7 +763,7 @@
/// UnswitchNontrivialCondition - We determined that the loop is profitable
/// to unswitch when LIC equal Val. Split it into loop versions and test the
/// condition outside of either loop. Return the loops created as Out1/Out2.
-bool LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
+void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
Loop *L) {
Function *F = loopHeader->getParent();
DEBUG(dbgs() << "loop-unswitch: Unswitching loop %"
@@ -800,8 +787,6 @@
SmallVector<BasicBlock*, 8> ExitBlocks;
L->getUniqueExitBlocks(ExitBlocks);
- if (HasIndirectBrsInPreds(ExitBlocks))
- return false;
// Split all of the edges from inside the loop to their exit blocks. Update
// the appropriate Phi nodes as we do so.
@@ -916,8 +901,6 @@
if (!LoopProcessWorklist.empty() && LoopProcessWorklist.back() == NewLoop &&
LICHandle && !isa<Constant>(LICHandle))
RewriteLoopBodyWithConditionConstant(NewLoop, LICHandle, Val, true);
-
- return true;
}
/// RemoveFromWorklist - Remove all instances of I from the worklist vector
diff --git a/lib/Transforms/Utils/LoopUnroll.cpp b/lib/Transforms/Utils/LoopUnroll.cpp
index 512b689..e15497a 100644
--- a/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/lib/Transforms/Utils/LoopUnroll.cpp
@@ -149,6 +149,12 @@
return false;
}
+ // Loops with indirectbr cannot be cloned.
+ if (!L->isSafeToClone()) {
+ DEBUG(dbgs() << " Can't unroll; Loop body cannot be cloned.\n");
+ return false;
+ }
+
BasicBlock *Header = L->getHeader();
BranchInst *BI = dyn_cast<BranchInst>(LatchBlock->getTerminator());