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Modify how immediates are removed from base expressions to deal with the fact

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that the symbolic evaluator is not always able to use subtraction to remove
expressions.  This makes the code faster, and fixes the last crash on 178.galgel.
Finally, add a statistic to see how many phi nodes are inserted.

On 178.galgel, we get the follow stats:

2562 loop-reduce  - Number of PHIs inserted
3927 loop-reduce  - Number of GEPs strength reduced


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@22662 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-08-04 22:34:05 +00:00
parent 2ac4fc0320
commit 26d91f1646
1 changed files with 40 additions and 25 deletions
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65
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -36,6 +36,7 @@ using namespace llvm;
namespace { namespace {
Statistic<> NumReduced ("loop-reduce", "Number of GEPs strength reduced"); Statistic<> NumReduced ("loop-reduce", "Number of GEPs strength reduced");
Statistic<> NumInserted("loop-reduce", "Number of PHIs inserted");
/// IVStrideUse - Keep track of one use of a strided induction variable, where /// IVStrideUse - Keep track of one use of a strided induction variable, where
/// the stride is stored externally. The Offset member keeps track of the /// the stride is stored externally. The Offset member keeps track of the
@ -433,38 +434,54 @@ static bool isTargetConstant(const SCEVHandle &V) {
return false; return false;
} }
/// GetImmediateValues - Look at Val, and pull out any additions of constants /// MoveImmediateValues - Look at Val, and pull out any additions of constants
/// that can fit into the immediate field of instructions in the target. /// that can fit into the immediate field of instructions in the target.
static SCEVHandle GetImmediateValues(SCEVHandle Val, bool isAddress, Loop *L) { /// Accumulate these immediate values into the Imm value.
if (isAddress && isTargetConstant(Val)) static void MoveImmediateValues(SCEVHandle &Val, SCEVHandle &Imm,
return Val; bool isAddress, Loop *L) {
if (SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) { if (SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
unsigned i = 0; std::vector<SCEVHandle> NewOps;
SCEVHandle Imm = SCEVUnknown::getIntegerSCEV(0, Val->getType()); NewOps.reserve(SAE->getNumOperands());
for (; i != SAE->getNumOperands(); ++i) for (unsigned i = 0; i != SAE->getNumOperands(); ++i)
if (isAddress && isTargetConstant(SAE->getOperand(i))) { if (isAddress && isTargetConstant(SAE->getOperand(i))) {
Imm = SCEVAddExpr::get(Imm, SAE->getOperand(i)); Imm = SCEVAddExpr::get(Imm, SAE->getOperand(i));
} else if (!SAE->getOperand(i)->isLoopInvariant(L)) { } else if (!SAE->getOperand(i)->isLoopInvariant(L)) {
// If this is a loop-variant expression, it must stay in the immediate // If this is a loop-variant expression, it must stay in the immediate
// field of the expression. // field of the expression.
Imm = SCEVAddExpr::get(Imm, SAE->getOperand(i)); Imm = SCEVAddExpr::get(Imm, SAE->getOperand(i));
} else {
NewOps.push_back(SAE->getOperand(i));
} }
return Imm; if (NewOps.empty())
Val = SCEVUnknown::getIntegerSCEV(0, Val->getType());
else
Val = SCEVAddExpr::get(NewOps);
return;
} else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) { } else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
// Try to pull immediates out of the start value of nested addrec's. // Try to pull immediates out of the start value of nested addrec's.
return GetImmediateValues(SARE->getStart(), isAddress, L); SCEVHandle Start = SARE->getStart();
MoveImmediateValues(Start, Imm, isAddress, L);
if (Start != SARE->getStart()) {
std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
Ops[0] = Start;
Val = SCEVAddRecExpr::get(Ops, SARE->getLoop());
}
return;
} }
if (!Val->isLoopInvariant(L)) { // Loop-variant expressions must stay in the immediate field of the
// If this is a loop-variant expression, it must stay in the immediate // expression.
// field of the expression. if ((isAddress && isTargetConstant(Val)) ||
return Val; !Val->isLoopInvariant(L)) {
Imm = SCEVAddExpr::get(Imm, Val);
Val = SCEVUnknown::getIntegerSCEV(0, Val->getType());
return;
} }
return SCEVUnknown::getIntegerSCEV(0, Val->getType()); // Otherwise, no immediates to move.
} }
/// StrengthReduceStridedIVUsers - Strength reduce all of the users of a single /// StrengthReduceStridedIVUsers - Strength reduce all of the users of a single
@ -502,14 +519,11 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(Value *Stride,
if (SI->getOperand(1) == UsersToProcess[i].second.OperandValToReplace) if (SI->getOperand(1) == UsersToProcess[i].second.OperandValToReplace)
isAddress = true; isAddress = true;
UsersToProcess[i].second.Imm = MoveImmediateValues(UsersToProcess[i].first, UsersToProcess[i].second.Imm,
GetImmediateValues(UsersToProcess[i].first, isAddress, L); isAddress, L);
UsersToProcess[i].first = SCEV::getMinusSCEV(UsersToProcess[i].first,
UsersToProcess[i].second.Imm);
DEBUG(std::cerr << "BASE: " << *UsersToProcess[i].first); assert(UsersToProcess[i].first->isLoopInvariant(L) &&
DEBUG(UsersToProcess[i].second.dump()); "Base value is not loop invariant!");
} }
SCEVExpander Rewriter(*SE, *LI); SCEVExpander Rewriter(*SE, *LI);
@ -545,6 +559,7 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(Value *Stride,
// Create a new Phi for this base, and stick it in the loop header. // Create a new Phi for this base, and stick it in the loop header.
const Type *ReplacedTy = Base->getType(); const Type *ReplacedTy = Base->getType();
PHINode *NewPHI = new PHINode(ReplacedTy, "iv.", PhiInsertBefore); PHINode *NewPHI = new PHINode(ReplacedTy, "iv.", PhiInsertBefore);
++NumInserted;
// Emit the initial base value into the loop preheader, and add it to the // Emit the initial base value into the loop preheader, and add it to the
// Phi node. // Phi node.