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Don't record the increment instruction; just recompute it from the Phi 

if needed. This simplifies the code a little, and is needed for an
upcoming refactoring.

llvm-svn: 66479
This commit is contained in:
Dan Gohman 2009-03-09 22:04:01 +00:00
parent 1349ab7c9f
commit f12436891e
1 changed files with 15 additions and 33 deletions
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48
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -97,11 +97,9 @@ namespace {
SCEVHandle Stride;
SCEVHandle Base;
PHINode *PHI;
Value *IncV;
IVExpr(const SCEVHandle &stride, const SCEVHandle &base, PHINode *phi,
Value *incv)
: Stride(stride), Base(base), PHI(phi), IncV(incv) {}
IVExpr(const SCEVHandle &stride, const SCEVHandle &base, PHINode *phi)
: Stride(stride), Base(base), PHI(phi) {}
};
/// IVsOfOneStride - This structure keeps track of all IV expression inserted
@ -109,9 +107,8 @@ namespace {
struct VISIBILITY_HIDDEN IVsOfOneStride {
std::vector<IVExpr> IVs;
void addIV(const SCEVHandle &Stride, const SCEVHandle &Base, PHINode *PHI,
Value *IncV) {
IVs.push_back(IVExpr(Stride, Base, PHI, IncV));
void addIV(const SCEVHandle &Stride, const SCEVHandle &Base, PHINode *PHI) {
IVs.push_back(IVExpr(Stride, Base, PHI));
}
};
@ -695,10 +692,7 @@ namespace {
/// Phi - The induction variable that performs the striding that
/// should be used for this user.
Value *Phi;
/// IncV - The post-incremented value of Phi.
Value *IncV;
PHINode *Phi;
// isUseOfPostIncrementedValue - True if this should use the
// post-incremented version of this IV, not the preincremented version.
@ -1587,13 +1581,11 @@ bool LoopStrengthReduce::ShouldUseFullStrengthReductionMode(
/// If NegateStride is true, the stride should be negated by using a
/// subtract instead of an add.
///
/// Return the created phi node, and return the step instruction by
/// reference in IncV.
/// Return the created phi node.
///
static PHINode *InsertAffinePhi(SCEVHandle Start, SCEVHandle Step,
const Loop *L,
SCEVExpander &Rewriter,
Value *&IncV) {
SCEVExpander &Rewriter) {
assert(Start->isLoopInvariant(L) && "New PHI start is not loop invariant!");
assert(Step->isLoopInvariant(L) && "New PHI stride is not loop invariant!");
@ -1615,6 +1607,7 @@ static PHINode *InsertAffinePhi(SCEVHandle Start, SCEVHandle Step,
// Insert an add instruction right before the terminator corresponding
// to the back-edge.
Value *StepV = Rewriter.expandCodeFor(IncAmount, Preheader->getTerminator());
Instruction *IncV;
if (isNegative) {
IncV = BinaryOperator::CreateSub(PN, StepV, "lsr.iv.next",
LatchBlock->getTerminator());
@ -1684,16 +1677,13 @@ LoopStrengthReduce::PrepareToStrengthReduceFully(
SCEVHandle Imm = UsersToProcess[i].Imm;
SCEVHandle Base = UsersToProcess[i].Base;
SCEVHandle Start = SE->getAddExpr(CommonExprs, Base, Imm);
Value *IncV;
PHINode *Phi = InsertAffinePhi(Start, Stride, L,
PreheaderRewriter,
IncV);
PreheaderRewriter);
// Loop over all the users with the same base.
do {
UsersToProcess[i].Base = SE->getIntegerSCEV(0, Stride->getType());
UsersToProcess[i].Imm = SE->getMinusSCEV(UsersToProcess[i].Imm, Imm);
UsersToProcess[i].Phi = Phi;
UsersToProcess[i].IncV = IncV;
assert(UsersToProcess[i].Imm->isLoopInvariant(L) &&
"ShouldUseFullStrengthReductionMode should reject this!");
} while (++i != e && Base == UsersToProcess[i].Base);
@ -1713,25 +1703,19 @@ LoopStrengthReduce::PrepareToStrengthReduceWithNewPhi(
SCEVExpander &PreheaderRewriter) {
DOUT << " Inserting new PHI:\n";
Value *IncV;
PHINode *Phi = InsertAffinePhi(SE->getUnknown(CommonBaseV),
Stride, L,
PreheaderRewriter,
IncV);
PreheaderRewriter);
// Remember this in case a later stride is multiple of this.
IVsByStride[Stride].addIV(Stride, CommonExprs, Phi, IncV);
IVsByStride[Stride].addIV(Stride, CommonExprs, Phi);
// All the users will share this new IV.
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
UsersToProcess[i].Phi = Phi;
UsersToProcess[i].IncV = IncV;
}
DOUT << " IV=";
DEBUG(WriteAsOperand(*DOUT, Phi, /*PrintType=*/false));
DOUT << ", INC=";
DEBUG(WriteAsOperand(*DOUT, IncV, /*PrintType=*/false));
DOUT << "\n";
}
@ -1749,10 +1733,8 @@ LoopStrengthReduce::PrepareToStrengthReduceFromSmallerStride(
<< " and BASE " << *ReuseIV.Base << "\n";
// All the users will share the reused IV.
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
UsersToProcess[i].Phi = ReuseIV.PHI;
UsersToProcess[i].IncV = ReuseIV.IncV;
}
Constant *C = dyn_cast<Constant>(CommonBaseV);
if (C &&
@ -1884,7 +1866,7 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
SCEVHandle RewriteFactor = SE->getIntegerSCEV(0, ReplacedTy);
IVExpr ReuseIV(SE->getIntegerSCEV(0, Type::Int32Ty),
SE->getIntegerSCEV(0, Type::Int32Ty),
0, 0);
0);
/// Choose a strength-reduction strategy and prepare for it by creating
/// the necessary PHIs and adjusting the bookkeeping.
@ -1957,7 +1939,7 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
// after the post-inc and use its value instead of the PHI.
Value *RewriteOp = User.Phi;
if (User.isUseOfPostIncrementedValue) {
RewriteOp = User.IncV;
RewriteOp = User.Phi->getIncomingValueForBlock(LatchBlock);
// If this user is in the loop, make sure it is the last thing in the
// loop to ensure it is dominated by the increment.