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Split MoveLoopVariantsToImediateField out from MoveImmediateValues. The

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first is a correctness thing, and the later is an optzn thing.  This also
is needed to support a future change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@22720 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-08-08 22:32:34 +00:00
parent d3ded2d8a7
commit 44b807e3c0
1 changed files with 65 additions and 23 deletions
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88
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -454,6 +454,45 @@ static bool isTargetConstant(const SCEVHandle &V) {
return false;
}
/// MoveLoopVariantsToImediateField - Move any subexpressions from Val that are
/// loop varying to the Imm operand.
static void MoveLoopVariantsToImediateField(SCEVHandle &Val, SCEVHandle &Imm,
Loop *L) {
if (Val->isLoopInvariant(L)) return; // Nothing to do.
if (SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
std::vector<SCEVHandle> NewOps;
NewOps.reserve(SAE->getNumOperands());
for (unsigned i = 0; i != SAE->getNumOperands(); ++i)
if (!SAE->getOperand(i)->isLoopInvariant(L)) {
// If this is a loop-variant expression, it must stay in the immediate
// field of the expression.
Imm = SCEVAddExpr::get(Imm, SAE->getOperand(i));
} else {
NewOps.push_back(SAE->getOperand(i));
}
if (NewOps.empty())
Val = SCEVUnknown::getIntegerSCEV(0, Val->getType());
else
Val = SCEVAddExpr::get(NewOps);
} else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
// Try to pull immediates out of the start value of nested addrec's.
SCEVHandle Start = SARE->getStart();
MoveLoopVariantsToImediateField(Start, Imm, L);
std::vector<SCEVHandle> Ops(SARE->op_begin(), SARE->op_end());
Ops[0] = Start;
Val = SCEVAddRecExpr::get(Ops, SARE->getLoop());
} else {
// Otherwise, all of Val is variant, move the whole thing over.
Imm = SCEVAddExpr::get(Imm, Val);
Val = SCEVUnknown::getIntegerSCEV(0, Val->getType());
}
}
/// MoveImmediateValues - Look at Val, and pull out any additions of constants
/// that can fit into the immediate field of instructions in the target.
/// Accumulate these immediate values into the Imm value.
@ -504,6 +543,7 @@ static void MoveImmediateValues(SCEVHandle &Val, SCEVHandle &Imm,
// Otherwise, no immediates to move.
}
/// StrengthReduceStridedIVUsers - Strength reduce all of the users of a single
/// stride of IV. All of the users may have different starting values, and this
/// may not be the only stride (we know it is if isOnlyStride is true).
@ -528,25 +568,17 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(Value *Stride,
Uses.Users[i].OperandValToReplace,
ZeroBase,
Uses.Users[i].isUseOfPostIncrementedValue)));
// First pass, figure out what we can represent in the immediate fields of
// instructions. If we can represent anything there, move it to the imm
// fields of the BasedUsers.
// Move any loop invariant operands from the offset field to the immediate
// field of the use, so that we don't try to use something before it is
// computed.
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
// Addressing modes can be folded into loads and stores. Be careful that
// the store is through the expression, not of the expression though.
bool isAddress = isa<LoadInst>(UsersToProcess[i].second.Inst);
if (StoreInst *SI = dyn_cast<StoreInst>(UsersToProcess[i].second.Inst))
if (SI->getOperand(1) == UsersToProcess[i].second.OperandValToReplace)
isAddress = true;
MoveImmediateValues(UsersToProcess[i].first, UsersToProcess[i].second.Imm,
isAddress, L);
MoveLoopVariantsToImediateField(UsersToProcess[i].first,
UsersToProcess[i].second.Imm, L);
assert(UsersToProcess[i].first->isLoopInvariant(L) &&
"Base value is not loop invariant!");
}
SCEVExpander Rewriter(*SE, *LI);
SCEVExpander PreheaderRewriter(*SE, *LI);
@ -561,16 +593,26 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(Value *Stride,
"This loop isn't canonicalized right");
BasicBlock *LatchBlock =
SomeLoopPHI->getIncomingBlock(SomeLoopPHI->getIncomingBlock(0) == Preheader);
// Next, figure out what we can represent in the immediate fields of
// instructions. If we can represent anything there, move it to the imm
// fields of the BasedUsers.
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
// Addressing modes can be folded into loads and stores. Be careful that
// the store is through the expression, not of the expression though.
bool isAddress = isa<LoadInst>(UsersToProcess[i].second.Inst);
if (StoreInst *SI = dyn_cast<StoreInst>(UsersToProcess[i].second.Inst))
if (SI->getOperand(1) == UsersToProcess[i].second.OperandValToReplace)
isAddress = true;
MoveImmediateValues(UsersToProcess[i].first, UsersToProcess[i].second.Imm,
isAddress, L);
}
DEBUG(std::cerr << "INSERTING IVs of STRIDE " << *Stride << ":\n");
// FIXME: This loop needs increasing levels of intelligence.
// STAGE 0: just emit everything as its own base.
// STAGE 1: factor out common vars from bases, and try and push resulting
// constants into Imm field. <-- We are here
// STAGE 2: factor out large constants to try and make more constants
// acceptable for target loads and stores.
// Sort by the base value, so that all IVs with identical bases are next to
// each other.
std::sort(UsersToProcess.begin(), UsersToProcess.end());