//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "loop-rotate"
#include "llvm/Transforms/Scalar.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/AssumptionTracker.h"
#include "llvm/Analysis/CodeMetrics.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/IR/CFG.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IntrinsicInst.h"
-#include "llvm/Support/CFG.h"
+#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/ValueMapper.h"
using namespace llvm;
-#define MAX_HEADER_SIZE 16
+#define DEBUG_TYPE "loop-rotate"
+
+static cl::opt<unsigned>
+DefaultRotationThreshold("rotation-max-header-size", cl::init(16), cl::Hidden,
+ cl::desc("The default maximum header size for automatic loop rotation"));
STATISTIC(NumRotated, "Number of loops rotated");
namespace {
class LoopRotate : public LoopPass {
public:
static char ID; // Pass ID, replacement for typeid
- LoopRotate() : LoopPass(ID) {
+ LoopRotate(int SpecifiedMaxHeaderSize = -1) : LoopPass(ID) {
initializeLoopRotatePass(*PassRegistry::getPassRegistry());
+ if (SpecifiedMaxHeaderSize == -1)
+ MaxHeaderSize = DefaultRotationThreshold;
+ else
+ MaxHeaderSize = unsigned(SpecifiedMaxHeaderSize);
}
// LCSSA form makes instruction renaming easier.
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.addRequired<AssumptionTracker>();
AU.addPreserved<DominatorTreeWrapperPass>();
AU.addRequired<LoopInfo>();
AU.addPreserved<LoopInfo>();
AU.addRequired<TargetTransformInfo>();
}
- bool runOnLoop(Loop *L, LPPassManager &LPM);
+ bool runOnLoop(Loop *L, LPPassManager &LPM) override;
bool simplifyLoopLatch(Loop *L);
bool rotateLoop(Loop *L, bool SimplifiedLatch);
private:
+ unsigned MaxHeaderSize;
LoopInfo *LI;
const TargetTransformInfo *TTI;
+ AssumptionTracker *AT;
};
}
char LoopRotate::ID = 0;
INITIALIZE_PASS_BEGIN(LoopRotate, "loop-rotate", "Rotate Loops", false, false)
INITIALIZE_AG_DEPENDENCY(TargetTransformInfo)
+INITIALIZE_PASS_DEPENDENCY(AssumptionTracker)
INITIALIZE_PASS_DEPENDENCY(LoopInfo)
INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
INITIALIZE_PASS_DEPENDENCY(LCSSA)
INITIALIZE_PASS_END(LoopRotate, "loop-rotate", "Rotate Loops", false, false)
-Pass *llvm::createLoopRotatePass() { return new LoopRotate(); }
+Pass *llvm::createLoopRotatePass(int MaxHeaderSize) {
+ return new LoopRotate(MaxHeaderSize);
+}
/// Rotate Loop L as many times as possible. Return true if
/// the loop is rotated at least once.
if (skipOptnoneFunction(L))
return false;
+ // Save the loop metadata.
+ MDNode *LoopMD = L->getLoopID();
+
LI = &getAnalysis<LoopInfo>();
TTI = &getAnalysis<TargetTransformInfo>();
+ AT = &getAnalysis<AssumptionTracker>();
// Simplify the loop latch before attempting to rotate the header
// upward. Rotation may not be needed if the loop tail can be folded into the
MadeChange = true;
SimplifiedLatch = false;
}
+
+ // Restore the loop metadata.
+ // NB! We presume LoopRotation DOESN'T ADD its own metadata.
+ if ((MadeChange || SimplifiedLatch) && LoopMD)
+ L->setLoopID(LoopMD);
+
return MadeChange;
}
for (Value::use_iterator UI = OrigHeaderVal->use_begin(),
UE = OrigHeaderVal->use_end(); UI != UE; ) {
// Grab the use before incrementing the iterator.
- Use &U = UI.getUse();
+ Use &U = *UI;
// Increment the iterator before removing the use from the list.
++UI;
}
}
-/// Determine whether the instructions in this range my be safely and cheaply
+/// Determine whether the instructions in this range may be safely and cheaply
/// speculated. This is not an important enough situation to develop complex
/// heuristics. We handle a single arithmetic instruction along with any type
/// conversions.
/// Fold the loop tail into the loop exit by speculating the loop tail
/// instructions. Typically, this is a single post-increment. In the case of a
/// simple 2-block loop, hoisting the increment can be much better than
-/// duplicating the entire loop header. In the cast of loops with early exits,
+/// duplicating the entire loop header. In the case of loops with early exits,
/// rotation will not work anyway, but simplifyLoopLatch will put the loop in
/// canonical form so downstream passes can handle it.
///
BasicBlock *OrigLatch = L->getLoopLatch();
BranchInst *BI = dyn_cast<BranchInst>(OrigHeader->getTerminator());
- if (BI == 0 || BI->isUnconditional())
+ if (!BI || BI->isUnconditional())
return false;
// If the loop header is not one of the loop exiting blocks then
// If the loop latch already contains a branch that leaves the loop then the
// loop is already rotated.
- if (OrigLatch == 0)
+ if (!OrigLatch)
return false;
// Rotate if either the loop latch does *not* exit the loop, or if the loop
// Check size of original header and reject loop if it is very big or we can't
// duplicate blocks inside it.
{
+ SmallPtrSet<const Value *, 32> EphValues;
+ CodeMetrics::collectEphemeralValues(L, AT, EphValues);
+
CodeMetrics Metrics;
- Metrics.analyzeBasicBlock(OrigHeader, *TTI);
+ Metrics.analyzeBasicBlock(OrigHeader, *TTI, EphValues);
if (Metrics.notDuplicatable) {
DEBUG(dbgs() << "LoopRotation: NOT rotating - contains non-duplicatable"
<< " instructions: "; L->dump());
return false;
}
- if (Metrics.NumInsts > MAX_HEADER_SIZE)
+ if (Metrics.NumInsts > MaxHeaderSize)
return false;
}
// If the loop could not be converted to canonical form, it must have an
// indirectbr in it, just give up.
- if (OrigPreheader == 0)
+ if (!OrigPreheader)
return false;
// Anything ScalarEvolution may know about this loop or the PHI nodes
// With the operands remapped, see if the instruction constant folds or is
// otherwise simplifyable. This commonly occurs because the entry from PHI
// nodes allows icmps and other instructions to fold.
+ // FIXME: Provide DL, TLI, DT, AT to SimplifyInstruction.
Value *V = SimplifyInstruction(C);
if (V && LI->replacementPreservesLCSSAForm(C, V)) {
// If so, then delete the temporary instruction and stick the folded value
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