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-rw-r--r--llvm/include/llvm/Analysis/ScalarEvolution.h15
-rw-r--r--llvm/lib/Analysis/ScalarEvolution.cpp22
-rw-r--r--llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp16
-rw-r--r--llvm/lib/Transforms/Vectorize/LoopVectorize.cpp5
4 files changed, 48 insertions, 10 deletions
diff --git a/llvm/include/llvm/Analysis/ScalarEvolution.h b/llvm/include/llvm/Analysis/ScalarEvolution.h
index 1467ffeecc9..bc31b8e4c3f 100644
--- a/llvm/include/llvm/Analysis/ScalarEvolution.h
+++ b/llvm/include/llvm/Analysis/ScalarEvolution.h
@@ -742,6 +742,13 @@ namespace llvm {
bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS);
+ /// \brief Returns the maximum trip count of the loop if it is a single-exit
+ /// loop and we can compute a small maximum for that loop.
+ ///
+ /// Implemented in terms of the \c getSmallConstantTripCount overload with
+ /// the single exiting block passed to it. See that routine for details.
+ unsigned getSmallConstantTripCount(Loop *L);
+
/// getSmallConstantTripCount - Returns the maximum trip count of this loop
/// as a normal unsigned value. Returns 0 if the trip count is unknown or
/// not constant. This "trip count" assumes that control exits via
@@ -751,6 +758,14 @@ namespace llvm {
/// the loop exits prematurely via another branch.
unsigned getSmallConstantTripCount(Loop *L, BasicBlock *ExitingBlock);
+ /// \brief Returns the largest constant divisor of the trip count of the
+ /// loop if it is a single-exit loop and we can compute a small maximum for
+ /// that loop.
+ ///
+ /// Implemented in terms of the \c getSmallConstantTripMultiple overload with
+ /// the single exiting block passed to it. See that routine for details.
+ unsigned getSmallConstantTripMultiple(Loop *L);
+
/// getSmallConstantTripMultiple - Returns the largest constant divisor of
/// the trip count of this loop as a normal unsigned value, if
/// possible. This means that the actual trip count is always a multiple of
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index e40c2f2447a..b015481b76c 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -4367,6 +4367,14 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) {
// Iteration Count Computation Code
//
+unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L) {
+ if (BasicBlock *ExitingBB = L->getExitingBlock())
+ return getSmallConstantTripCount(L, ExitingBB);
+
+ // No trip count information for multiple exits.
+ return 0;
+}
+
/// getSmallConstantTripCount - Returns the maximum trip count of this loop as a
/// normal unsigned value. Returns 0 if the trip count is unknown or not
/// constant. Will also return 0 if the maximum trip count is very large (>=
@@ -4379,6 +4387,9 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) {
/// prematurely via another branch.
unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L,
BasicBlock *ExitingBlock) {
+ assert(ExitingBlock && "Must pass a non-null exiting block!");
+ assert(L->isLoopExiting(ExitingBlock) &&
+ "Exiting block must actually branch out of the loop!");
const SCEVConstant *ExitCount =
dyn_cast<SCEVConstant>(getExitCount(L, ExitingBlock));
if (!ExitCount)
@@ -4394,6 +4405,14 @@ unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L,
return ((unsigned)ExitConst->getZExtValue()) + 1;
}
+unsigned ScalarEvolution::getSmallConstantTripMultiple(Loop *L) {
+ if (BasicBlock *ExitingBB = L->getExitingBlock())
+ return getSmallConstantTripMultiple(L, ExitingBB);
+
+ // No trip multiple information for multiple exits.
+ return 0;
+}
+
/// getSmallConstantTripMultiple - Returns the largest constant divisor of the
/// trip count of this loop as a normal unsigned value, if possible. This
/// means that the actual trip count is always a multiple of the returned
@@ -4409,6 +4428,9 @@ unsigned ScalarEvolution::getSmallConstantTripCount(Loop *L,
unsigned
ScalarEvolution::getSmallConstantTripMultiple(Loop *L,
BasicBlock *ExitingBlock) {
+ assert(ExitingBlock && "Must pass a non-null exiting block!");
+ assert(L->isLoopExiting(ExitingBlock) &&
+ "Exiting block must actually branch out of the loop!");
const SCEV *ExitCount = getExitCount(L, ExitingBlock);
if (ExitCount == getCouldNotCompute())
return 1;
diff --git a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
index d83816a5a51..f60d9903a55 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -382,13 +382,15 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
// Find trip count and trip multiple if count is not available
unsigned TripCount = 0;
unsigned TripMultiple = 1;
- // Find "latch trip count". UnrollLoop assumes that control cannot exit
- // via the loop latch on any iteration prior to TripCount. The loop may exit
- // early via an earlier branch.
- BasicBlock *LatchBlock = L->getLoopLatch();
- if (LatchBlock) {
- TripCount = SE->getSmallConstantTripCount(L, LatchBlock);
- TripMultiple = SE->getSmallConstantTripMultiple(L, LatchBlock);
+ // If there are multiple exiting blocks but one of them is the latch, use the
+ // latch for the trip count estimation. Otherwise insist on a single exiting
+ // block for the trip count estimation.
+ BasicBlock *ExitingBlock = L->getLoopLatch();
+ if (!ExitingBlock || !L->isLoopExiting(ExitingBlock))
+ ExitingBlock = L->getExitingBlock();
+ if (ExitingBlock) {
+ TripCount = SE->getSmallConstantTripCount(L, ExitingBlock);
+ TripMultiple = SE->getSmallConstantTripMultiple(L, ExitingBlock);
}
// Select an initial unroll count. This may be reduced later based
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 68d4858662e..2004f62a80c 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -1360,8 +1360,7 @@ struct LoopVectorize : public FunctionPass {
// Check the loop for a trip count threshold:
// do not vectorize loops with a tiny trip count.
- BasicBlock *Latch = L->getLoopLatch();
- const unsigned TC = SE->getSmallConstantTripCount(L, Latch);
+ const unsigned TC = SE->getSmallConstantTripCount(L);
if (TC > 0u && TC < TinyTripCountVectorThreshold) {
DEBUG(dbgs() << "LV: Found a loop with a very small trip count. "
<< "This loop is not worth vectorizing.");
@@ -5352,7 +5351,7 @@ LoopVectorizationCostModel::selectVectorizationFactor(bool OptForSize) {
}
// Find the trip count.
- unsigned TC = SE->getSmallConstantTripCount(TheLoop, TheLoop->getLoopLatch());
+ unsigned TC = SE->getSmallConstantTripCount(TheLoop);
DEBUG(dbgs() << "LV: Found trip count: " << TC << '\n');
unsigned WidestType = getWidestType();
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