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Revert r97580; that's not the right way to fix this.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97639 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-03-03 04:36:42 +00:00
parent 6ba9554988
commit ed78dbafd0
2 changed files with 38 additions and 128 deletions
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160
lib/Analysis/ScalarEvolutionExpander.cpp
View File

@ -528,138 +528,48 @@ static bool isNonConstantNegative(const SCEV *F) {
return SC->getValue()->getValue().isNegative();
}
/// PickMostRelevantLoop - Given two loops pick the one that's most relevant for
/// SCEV expansion. If they are nested, this is the most nested. If they are
/// neighboring, pick the later.
static const Loop *PickMostRelevantLoop(const Loop *A, const Loop *B,
DominatorTree &DT) {
if (!A) return B;
if (!B) return A;
if (A->contains(B)) return B;
if (B->contains(A)) return A;
if (DT.dominates(A->getHeader(), B->getHeader())) return B;
if (DT.dominates(B->getHeader(), A->getHeader())) return A;
return A; // Arbitrarily break the tie.
}
/// GetRelevantLoop - Get the most relevant loop associated with the given
/// expression, according to PickMostRelevantLoop.
static const Loop *GetRelevantLoop(const SCEV *S, LoopInfo &LI,
DominatorTree &DT) {
if (isa<SCEVConstant>(S))
return 0;
if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
if (const Instruction *I = dyn_cast<Instruction>(U->getValue()))
return LI.getLoopFor(I->getParent());
return 0;
}
if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S)) {
const Loop *L = 0;
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
L = AR->getLoop();
for (SCEVNAryExpr::op_iterator I = N->op_begin(), E = N->op_end();
I != E; ++I)
L = PickMostRelevantLoop(L, GetRelevantLoop(*I, LI, DT), DT);
return L;
}
if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
return GetRelevantLoop(C->getOperand(), LI, DT);
if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S))
return PickMostRelevantLoop(GetRelevantLoop(D->getLHS(), LI, DT),
GetRelevantLoop(D->getRHS(), LI, DT),
DT);
llvm_unreachable("Unexpected SCEV type!");
}
namespace {
/// LoopCompare - Compare loops by PickMostRelevantLoop.
class LoopCompare {
DominatorTree &DT;
public:
explicit LoopCompare(DominatorTree &dt) : DT(dt) {}
bool operator()(std::pair<const Loop *, const SCEV *> LHS,
std::pair<const Loop *, const SCEV *> RHS) const {
// Compare loops with PickMostRelevantLoop.
if (LHS.first != RHS.first)
return PickMostRelevantLoop(LHS.first, RHS.first, DT) == LHS.first;
// If one operand is a non-constant negative and the other is not,
// put the non-constant negative on the right so that a sub can
// be used instead of a negate and add.
if (isNonConstantNegative(LHS.second)) {
if (!isNonConstantNegative(RHS.second))
return false;
} else if (isNonConstantNegative(RHS.second))
return true;
// Otherwise they are equivalent according to this comparison.
return false;
}
};
}
Value *SCEVExpander::visitAddExpr(const SCEVAddExpr *S) {
int NumOperands = S->getNumOperands();
const Type *Ty = SE.getEffectiveSCEVType(S->getType());
// Collect all the add operands in a loop, along with their associated loops.
// Iterate in reverse so that constants are emitted last, all else equal, and
// so that pointer operands are inserted first, which the code below relies on
// to form more involved GEPs.
SmallVector<std::pair<const Loop *, const SCEV *>, 8> OpsAndLoops;
for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(S->op_end()),
E(S->op_begin()); I != E; ++I)
OpsAndLoops.push_back(std::make_pair(GetRelevantLoop(*I, *SE.LI, *SE.DT),
*I));
// Find the index of an operand to start with. Choose the operand with
// pointer type, if there is one, or the last operand otherwise.
int PIdx = 0;
for (; PIdx != NumOperands - 1; ++PIdx)
if (S->getOperand(PIdx)->getType()->isPointerTy()) break;
// Sort by loop. Use a stable sort so that constants follow non-constants and
// pointer operands precede non-pointer operands.
std::stable_sort(OpsAndLoops.begin(), OpsAndLoops.end(), LoopCompare(*SE.DT));
// Expand code for the operand that we chose.
Value *V = expand(S->getOperand(PIdx));
// Emit instructions to add all the operands. Hoist as much as possible
// out of loops, and form meaningful getelementptrs where possible.
Value *Sum = 0;
for (SmallVectorImpl<std::pair<const Loop *, const SCEV *> >::iterator
I = OpsAndLoops.begin(), E = OpsAndLoops.end(); I != E; ) {
const Loop *CurLoop = I->first;
const SCEV *Op = I->second;
if (!Sum) {
// This is the first operand. Just expand it.
Sum = expand(Op);
++I;
} else if (const PointerType *PTy = dyn_cast<PointerType>(Sum->getType())) {
// The running sum expression is a pointer. Try to form a getelementptr
// at this level with that as the base.
SmallVector<const SCEV *, 4> NewOps;
for (; I != E && I->first == CurLoop; ++I)
NewOps.push_back(I->second);
Sum = expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, Sum);
} else if (const PointerType *PTy = dyn_cast<PointerType>(Op->getType())) {
// The running sum is an integer, and there's a pointer at this level.
// Try to form a getelementptr.
SmallVector<const SCEV *, 4> NewOps;
NewOps.push_back(SE.getUnknown(Sum));
for (++I; I != E && I->first == CurLoop; ++I)
NewOps.push_back(I->second);
Sum = expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, expand(Op));
} else if (isNonConstantNegative(Op)) {
// Instead of doing a negate and add, just do a subtract.
Value *W = expandCodeFor(SE.getNegativeSCEV(Op), Ty);
Sum = InsertNoopCastOfTo(Sum, Ty);
Sum = InsertBinop(Instruction::Sub, Sum, W);
++I;
} else {
// A simple add.
Value *W = expandCodeFor(Op, Ty);
Sum = InsertNoopCastOfTo(Sum, Ty);
Sum = InsertBinop(Instruction::Add, Sum, W);
++I;
}
// Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the
// comments on expandAddToGEP for details.
if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) {
// Take the operand at PIdx out of the list.
const SmallVectorImpl<const SCEV *> &Ops = S->getOperands();
SmallVector<const SCEV *, 8> NewOps;
NewOps.insert(NewOps.end(), Ops.begin(), Ops.begin() + PIdx);
NewOps.insert(NewOps.end(), Ops.begin() + PIdx + 1, Ops.end());
// Make a GEP.
return expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, V);
}
return Sum;
// Otherwise, we'll expand the rest of the SCEVAddExpr as plain integer
// arithmetic.
V = InsertNoopCastOfTo(V, Ty);
// Emit a bunch of add instructions
for (int i = NumOperands-1; i >= 0; --i) {
if (i == PIdx) continue;
const SCEV *Op = S->getOperand(i);
if (isNonConstantNegative(Op)) {
Value *W = expandCodeFor(SE.getNegativeSCEV(Op), Ty);
V = InsertBinop(Instruction::Sub, V, W);
} else {
Value *W = expandCodeFor(Op, Ty);
V = InsertBinop(Instruction::Add, V, W);
}
}
return V;
}
Value *SCEVExpander::visitMulExpr(const SCEVMulExpr *S) {

6
test/CodeGen/X86/pr3495.ll
View File

@ -1,6 +1,6 @@
; RUN: llc < %s -march=x86 -stats |& not grep {Number of loads added}
; RUN: llc < %s -march=x86 -stats |& not grep {Number of register spills}
; RUN: llc < %s -march=x86 -stats |& grep {Number of machine instrs printed} | grep 32
; RUN: llc < %s -march=x86 -stats |& grep {Number of loads added} | grep 2
; RUN: llc < %s -march=x86 -stats |& grep {Number of register spills} | grep 1
; RUN: llc < %s -march=x86 -stats |& grep {Number of machine instrs printed} | grep 34
; PR3495
target triple = "i386-pc-linux-gnu"