#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/iOperators.h"
#include "llvm/iPHINode.h"
+#include "llvm/iMemory.h"
#include "llvm/Support/InstVisitor.h"
#include "llvm/Support/CFG.h"
#include "Support/STLExtras.h"
#include "Support/StatisticReporter.h"
#include <algorithm>
+using std::string;
static Statistic<> NumHoistedNPH("licm\t\t- Number of insts hoisted to multiple"
" loop preds (bad, no loop pre-header)");
static Statistic<> NumHoistedPH("licm\t\t- Number of insts hoisted to a loop "
"pre-header");
+static Statistic<> NumHoistedLoads("licm\t\t- Number of load insts hoisted");
namespace {
struct LICM : public FunctionPass, public InstVisitor<LICM> {
- const char *getPassName() const { return "Loop Invariant Code Motion"; }
-
virtual bool runOnFunction(Function &F);
// This transformation requires natural loop information...
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.preservesCFG();
- AU.addRequired(LoopInfo::ID);
+ AU.addRequired<LoopInfo>();
+ AU.addRequired<AliasAnalysis>();
}
private:
//
std::vector<BasicBlock*> LoopPreds, LoopBackEdges;
- Loop *CurLoop; // The current loop we are working on...
- bool Changed; // Set to true when we change anything.
+ Loop *CurLoop; // The current loop we are working on...
+ bool Changed; // Set to true when we change anything.
+ AliasAnalysis *AA; // Currently AliasAnalysis information
// visitLoop - Hoist expressions out of the specified loop...
void visitLoop(Loop *L);
//
void hoist(Instruction &I);
+ // pointerInvalidatedByLoop - Return true if the body of this loop may store
+ // into the memory location pointed to by V.
+ //
+ bool pointerInvalidatedByLoop(Value *V);
+
// isLoopInvariant - Return true if the specified value is loop invariant
inline bool isLoopInvariant(Value *V) {
if (Instruction *I = dyn_cast<Instruction>(V))
// the specified instruction types are hoisted.
//
friend class InstVisitor<LICM>;
- void visitUnaryOperator(Instruction &I) {
- if (isLoopInvariant(I.getOperand(0))) hoist(I);
- }
void visitBinaryOperator(Instruction &I) {
if (isLoopInvariant(I.getOperand(0)) && isLoopInvariant(I.getOperand(1)))
hoist(I);
}
-
- void visitCastInst(CastInst &I) { visitUnaryOperator((Instruction&)I); }
+ void visitCastInst(CastInst &CI) {
+ Instruction &I = (Instruction&)CI;
+ if (isLoopInvariant(I.getOperand(0))) hoist(I);
+ }
void visitShiftInst(ShiftInst &I) { visitBinaryOperator((Instruction&)I); }
+ void visitLoadInst(LoadInst &LI) {
+ if (isLoopInvariant(LI.getOperand(0)) &&
+ !pointerInvalidatedByLoop(LI.getOperand(0)))
+ hoist(LI);
+ }
+
void visitGetElementPtrInst(GetElementPtrInst &GEPI) {
Instruction &I = (Instruction&)GEPI;
for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
hoist(I);
}
};
+
+ RegisterOpt<LICM> X("licm", "Loop Invariant Code Motion");
}
Pass *createLICMPass() { return new LICM(); }
const std::vector<Loop*> &TopLevelLoops =
getAnalysis<LoopInfo>().getTopLevelLoops();
+ // Get our alias analysis information...
+ AA = &getAnalysis<AliasAnalysis>();
+
// Traverse loops in postorder, hoisting expressions out of the deepest loops
// first.
//
string InstName = Inst.getName();
Inst.setName("");
+ if (isa<LoadInst>(Inst))
+ ++NumHoistedLoads;
+
// The common case is that we have a pre-header. Generate special case code
// that is faster if that is the case.
//
// No loop pre-header, insert a PHI node into header to capture all of the
// incoming versions of the value.
//
- PHINode *LoopVal = new PHINode(Inst.getType(), InstName+".phi");
-
- // Insert the new PHI node into the loop header...
- Header->getInstList().push_front(LoopVal);
+ PHINode *LoopVal = new PHINode(Inst.getType(), InstName+".phi",
+ Header->begin());
// Insert cloned versions of the instruction into all of the loop preds.
for (unsigned i = 0, e = LoopPreds.size(); i != e; ++i) {
Changed = true;
}
+// pointerInvalidatedByLoop - Return true if the body of this loop may store
+// into the memory location pointed to by V.
+//
+bool LICM::pointerInvalidatedByLoop(Value *V) {
+ // Check to see if any of the basic blocks in CurLoop invalidate V.
+ for (unsigned i = 0, e = CurLoop->getBlocks().size(); i != e; ++i)
+ if (AA->canBasicBlockModify(*CurLoop->getBlocks()[i], V))
+ return true;
+ return false;
+}