aboutsummaryrefslogtreecommitdiff
path: root/lib/Transforms/Scalar/LoopStrengthReduce.cpp
diff options
context:
space:
mode:
Diffstat (limited to 'lib/Transforms/Scalar/LoopStrengthReduce.cpp')
-rw-r--r--lib/Transforms/Scalar/LoopStrengthReduce.cpp100
1 files changed, 70 insertions, 30 deletions
diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 8c2e9b6ff5..600937693b 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -24,14 +24,18 @@
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
+#include "llvm/Type.h"
#include "llvm/DerivedTypes.h"
+#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/IVUsers.h"
+#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolutionExpander.h"
#include "llvm/Transforms/Utils/AddrModeMatcher.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/CFG.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ValueHandle.h"
@@ -81,6 +85,8 @@ namespace {
class LoopStrengthReduce : public LoopPass {
IVUsers *IU;
+ LoopInfo *LI;
+ DominatorTree *DT;
ScalarEvolution *SE;
bool Changed;
@@ -88,6 +94,10 @@ namespace {
/// particular stride.
std::map<const SCEV *, IVsOfOneStride> IVsByStride;
+ /// StrideNoReuse - Keep track of all the strides whose ivs cannot be
+ /// reused (nor should they be rewritten to reuse other strides).
+ SmallSet<const SCEV *, 4> StrideNoReuse;
+
/// DeadInsts - Keep track of instructions we may have made dead, so that
/// we can remove them after we are done working.
SmallVector<WeakVH, 16> DeadInsts;
@@ -99,7 +109,8 @@ namespace {
public:
static char ID; // Pass ID, replacement for typeid
explicit LoopStrengthReduce(const TargetLowering *tli = NULL) :
- LoopPass(&ID), TLI(tli) {}
+ LoopPass(&ID), TLI(tli) {
+ }
bool runOnLoop(Loop *L, LPPassManager &LPM);
@@ -107,11 +118,13 @@ namespace {
// We split critical edges, so we change the CFG. However, we do update
// many analyses if they are around.
AU.addPreservedID(LoopSimplifyID);
- AU.addPreserved("loops");
- AU.addPreserved("domfrontier");
- AU.addPreserved("domtree");
+ AU.addPreserved<LoopInfo>();
+ AU.addPreserved<DominanceFrontier>();
+ AU.addPreserved<DominatorTree>();
AU.addRequiredID(LoopSimplifyID);
+ AU.addRequired<LoopInfo>();
+ AU.addRequired<DominatorTree>();
AU.addRequired<ScalarEvolution>();
AU.addPreserved<ScalarEvolution>();
AU.addRequired<IVUsers>();
@@ -215,17 +228,19 @@ void LoopStrengthReduce::DeleteTriviallyDeadInstructions() {
if (DeadInsts.empty()) return;
while (!DeadInsts.empty()) {
- Instruction *I = dyn_cast_or_null<Instruction>(DeadInsts.pop_back_val());
+ Instruction *I = dyn_cast_or_null<Instruction>(DeadInsts.back());
+ DeadInsts.pop_back();
if (I == 0 || !isInstructionTriviallyDead(I))
continue;
- for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
+ for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) {
if (Instruction *U = dyn_cast<Instruction>(*OI)) {
*OI = 0;
if (U->use_empty())
DeadInsts.push_back(U);
}
+ }
I->eraseFromParent();
Changed = true;
@@ -285,6 +300,9 @@ namespace {
/// BasedUser - For a particular base value, keep information about how we've
/// partitioned the expression so far.
struct BasedUser {
+ /// SE - The current ScalarEvolution object.
+ ScalarEvolution *SE;
+
/// Base - The Base value for the PHI node that needs to be inserted for
/// this use. As the use is processed, information gets moved from this
/// field to the Imm field (below). BasedUser values are sorted by this
@@ -316,9 +334,9 @@ namespace {
bool isUseOfPostIncrementedValue;
BasedUser(IVStrideUse &IVSU, ScalarEvolution *se)
- : Base(IVSU.getOffset()), Inst(IVSU.getUser()),
+ : SE(se), Base(IVSU.getOffset()), Inst(IVSU.getUser()),
OperandValToReplace(IVSU.getOperandValToReplace()),
- Imm(se->getIntegerSCEV(0, Base->getType())),
+ Imm(SE->getIntegerSCEV(0, Base->getType())),
isUseOfPostIncrementedValue(IVSU.isUseOfPostIncrementedValue()) {}
// Once we rewrite the code to insert the new IVs we want, update the
@@ -327,14 +345,14 @@ namespace {
void RewriteInstructionToUseNewBase(const SCEV *const &NewBase,
Instruction *InsertPt,
SCEVExpander &Rewriter, Loop *L, Pass *P,
- SmallVectorImpl<WeakVH> &DeadInsts,
- ScalarEvolution *SE);
+ LoopInfo &LI,
+ SmallVectorImpl<WeakVH> &DeadInsts);
Value *InsertCodeForBaseAtPosition(const SCEV *const &NewBase,
const Type *Ty,
SCEVExpander &Rewriter,
- Instruction *IP,
- ScalarEvolution *SE);
+ Instruction *IP, Loop *L,
+ LoopInfo &LI);
void dump() const;
};
}
@@ -348,12 +366,27 @@ void BasedUser::dump() const {
Value *BasedUser::InsertCodeForBaseAtPosition(const SCEV *const &NewBase,
const Type *Ty,
SCEVExpander &Rewriter,
- Instruction *IP,
- ScalarEvolution *SE) {
- Value *Base = Rewriter.expandCodeFor(NewBase, 0, IP);
+ Instruction *IP, Loop *L,
+ LoopInfo &LI) {
+ // Figure out where we *really* want to insert this code. In particular, if
+ // the user is inside of a loop that is nested inside of L, we really don't
+ // want to insert this expression before the user, we'd rather pull it out as
+ // many loops as possible.
+ Instruction *BaseInsertPt = IP;
+
+ // Figure out the most-nested loop that IP is in.
+ Loop *InsertLoop = LI.getLoopFor(IP->getParent());
+
+ // If InsertLoop is not L, and InsertLoop is nested inside of L, figure out
+ // the preheader of the outer-most loop where NewBase is not loop invariant.
+ if (L->contains(IP->getParent()))
+ while (InsertLoop && NewBase->isLoopInvariant(InsertLoop)) {
+ BaseInsertPt = InsertLoop->getLoopPreheader()->getTerminator();
+ InsertLoop = InsertLoop->getParentLoop();
+ }
+
+ Value *Base = Rewriter.expandCodeFor(NewBase, 0, BaseInsertPt);
- // Wrap the base in a SCEVUnknown so that ScalarEvolution doesn't try to
- // re-analyze it.
const SCEV *NewValSCEV = SE->getUnknown(Base);
// Always emit the immediate into the same block as the user.
@@ -372,8 +405,8 @@ Value *BasedUser::InsertCodeForBaseAtPosition(const SCEV *const &NewBase,
void BasedUser::RewriteInstructionToUseNewBase(const SCEV *const &NewBase,
Instruction *NewBasePt,
SCEVExpander &Rewriter, Loop *L, Pass *P,
- SmallVectorImpl<WeakVH> &DeadInsts,
- ScalarEvolution *SE) {
+ LoopInfo &LI,
+ SmallVectorImpl<WeakVH> &DeadInsts) {
if (!isa<PHINode>(Inst)) {
// By default, insert code at the user instruction.
BasicBlock::iterator InsertPt = Inst;
@@ -402,7 +435,7 @@ void BasedUser::RewriteInstructionToUseNewBase(const SCEV *const &NewBase,
}
Value *NewVal = InsertCodeForBaseAtPosition(NewBase,
OperandValToReplace->getType(),
- Rewriter, InsertPt, SE);
+ Rewriter, InsertPt, L, LI);
// Replace the use of the operand Value with the new Phi we just created.
Inst->replaceUsesOfWith(OperandValToReplace, NewVal);
@@ -464,7 +497,7 @@ void BasedUser::RewriteInstructionToUseNewBase(const SCEV *const &NewBase,
PHIPred->getTerminator() :
OldLoc->getParent()->getTerminator();
Code = InsertCodeForBaseAtPosition(NewBase, PN->getType(),
- Rewriter, InsertPt, SE);
+ Rewriter, InsertPt, L, LI);
DEBUG(errs() << " Changing PHI use to ");
DEBUG(WriteAsOperand(errs(), Code, /*PrintType=*/false));
@@ -940,13 +973,17 @@ const SCEV *LoopStrengthReduce::CheckForIVReuse(bool HasBaseReg,
const SCEV *const &Stride,
IVExpr &IV, const Type *Ty,
const std::vector<BasedUser>& UsersToProcess) {
+ if (StrideNoReuse.count(Stride))
+ return SE->getIntegerSCEV(0, Stride->getType());
+
if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Stride)) {
int64_t SInt = SC->getValue()->getSExtValue();
for (unsigned NewStride = 0, e = IU->StrideOrder.size();
NewStride != e; ++NewStride) {
std::map<const SCEV *, IVsOfOneStride>::iterator SI =
IVsByStride.find(IU->StrideOrder[NewStride]);
- if (SI == IVsByStride.end() || !isa<SCEVConstant>(SI->first))
+ if (SI == IVsByStride.end() || !isa<SCEVConstant>(SI->first) ||
+ StrideNoReuse.count(SI->first))
continue;
// The other stride has no uses, don't reuse it.
std::map<const SCEV *, IVUsersOfOneStride *>::iterator UI =
@@ -1705,8 +1742,8 @@ LoopStrengthReduce::StrengthReduceIVUsersOfStride(const SCEV *const &Stride,
RewriteExpr = SE->getAddExpr(RewriteExpr, SE->getUnknown(BaseV));
User.RewriteInstructionToUseNewBase(RewriteExpr, NewBasePt,
- Rewriter, L, this,
- DeadInsts, SE);
+ Rewriter, L, this, *LI,
+ DeadInsts);
// Mark old value we replaced as possibly dead, so that it is eliminated
// if we just replaced the last use of that value.
@@ -2670,6 +2707,8 @@ bool LoopStrengthReduce::OptimizeLoopCountIV(Loop *L) {
bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) {
IU = &getAnalysis<IVUsers>();
+ LI = &getAnalysis<LoopInfo>();
+ DT = &getAnalysis<DominatorTree>();
SE = &getAnalysis<ScalarEvolution>();
Changed = false;
@@ -2715,14 +2754,15 @@ bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) {
// After all sharing is done, see if we can adjust the loop to test against
// zero instead of counting up to a maximum. This is usually faster.
OptimizeLoopCountIV(L);
+ }
- // We're done analyzing this loop; release all the state we built up for it.
- IVsByStride.clear();
+ // We're done analyzing this loop; release all the state we built up for it.
+ IVsByStride.clear();
+ StrideNoReuse.clear();
- // Clean up after ourselves
- if (!DeadInsts.empty())
- DeleteTriviallyDeadInstructions();
- }
+ // Clean up after ourselves
+ if (!DeadInsts.empty())
+ DeleteTriviallyDeadInstructions();
// At this point, it is worth checking to see if any recurrence PHIs are also
// dead, so that we can remove them as well.
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2025-04-30 15:47:28 +0000