Previously, RecursivelyDeleteDeadInstructions provided an option
of returning a list of pointers to Values that are deleted. This was
unsafe, because the pointers in the list are, by nature of what
RecursivelyDeleteDeadInstructions does, always dangling. Replace this
with a simple callback mechanism. This may eventually be removed if
all clients can reasonably be expected to use CallbackVH.
Use this to factor out the dead-phi-cycle-elimination code from LSR
utility function, and generalize it to use the
RecursivelyDeleteTriviallyDeadInstructions utility function.
This makes LSR more aggressive about eliminating dead PHI cycles;
adjust tests to either be less trivial or to simply expect fewer
instructions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70636 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index e550200..b940665 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -32,6 +32,7 @@
#include "llvm/Support/Debug.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/ValueHandle.h"
#include "llvm/Target/TargetLowering.h"
#include <algorithm>
using namespace llvm;
@@ -2138,6 +2139,7 @@
CondUse = &IVUsesByStride[*NewStride].Users.back();
CondStride = NewStride;
++NumEliminated;
+ Changed = true;
}
return Cond;
@@ -2501,44 +2503,21 @@
StrideOrder.clear();
// Clean up after ourselves
- if (!DeadInsts.empty()) {
+ if (!DeadInsts.empty())
DeleteTriviallyDeadInstructions();
- BasicBlock::iterator I = L->getHeader()->begin();
- while (PHINode *PN = dyn_cast<PHINode>(I++)) {
- // At this point, we know that we have killed one or more IV users.
- // It is worth checking to see if the cannonical indvar is also
- // dead, so that we can remove it as well.
- //
- // We can remove a PHI if it is on a cycle in the def-use graph
- // where each node in the cycle has degree one, i.e. only one use,
- // and is an instruction with no side effects.
- //
- // FIXME: this needs to eliminate an induction variable even if it's being
- // compared against some value to decide loop termination.
- if (!PN->hasOneUse())
- continue;
-
- SmallPtrSet<PHINode *, 4> PHIs;
- for (Instruction *J = dyn_cast<Instruction>(*PN->use_begin());
- J && J->hasOneUse() && !J->mayWriteToMemory();
- J = dyn_cast<Instruction>(*J->use_begin())) {
- // If we find the original PHI, we've discovered a cycle.
- if (J == PN) {
- // Break the cycle and mark the PHI for deletion.
- SE->deleteValueFromRecords(PN);
- PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
- DeadInsts.push_back(PN);
- Changed = true;
- break;
- }
- // If we find a PHI more than once, we're on a cycle that
- // won't prove fruitful.
- if (isa<PHINode>(J) && !PHIs.insert(cast<PHINode>(J)))
- break;
- }
+ // At this point, it is worth checking to see if any recurrence PHIs are also
+ // dead, so that we can remove them as well. To keep ScalarEvolution
+ // current, use a ValueDeletionListener class.
+ struct LSRListener : public ValueDeletionListener {
+ ScalarEvolution &SE;
+ explicit LSRListener(ScalarEvolution &se) : SE(se) {}
+
+ virtual void ValueWillBeDeleted(Value *V) {
+ SE.deleteValueFromRecords(V);
}
- DeleteTriviallyDeadInstructions();
- }
+ } VDL(*SE);
+ DeleteDeadPHIs(L->getHeader(), &VDL);
+
return Changed;
}