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Extended replaceCongruentPhis to handle mixed phi types. 

llvm-svn: 147707
This commit is contained in:
Andrew Trick 2012-01-07 01:12:09 +00:00
parent 44803326d4
commit 5adedf5d47
4 changed files with 69 additions and 18 deletions
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5
llvm/include/llvm/Analysis/ScalarEvolutionExpander.h
View File

@ -22,6 +22,8 @@
#include <set>
namespace llvm {
class TargetLowering;
/// SCEVExpander - This class uses information about analyze scalars to
/// rewrite expressions in canonical form.
///
@ -115,7 +117,8 @@ namespace llvm {
/// replaceCongruentIVs - replace congruent phis with their most canonical
/// representative. Return the number of phis eliminated.
unsigned replaceCongruentIVs(Loop *L, const DominatorTree *DT,
SmallVectorImpl<WeakVH> &DeadInsts);
SmallVectorImpl<WeakVH> &DeadInsts,
const TargetLowering *TLI = NULL);
/// expandCodeFor - Insert code to directly compute the specified SCEV
/// expression into the program. The inserted code is inserted into the

74
llvm/lib/Analysis/ScalarEvolutionExpander.cpp
View File

@ -19,6 +19,7 @@
#include "llvm/LLVMContext.h"
#include "llvm/Support/Debug.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/ADT/STLExtras.h"
using namespace llvm;
@ -1557,6 +1558,15 @@ bool SCEVExpander::hoistStep(Instruction *IncV, Instruction *InsertPos,
return true;
}
/// Sort Phis by integer width for replaceCongruentIVs.
static bool width_descending(PHINode *lhs, PHINode *rhs) {
// Put pointers at the back and make sure pointer < pointer = false.
if (!lhs->getType()->isIntegerTy() || !rhs->getType()->isIntegerTy())
return rhs->getType()->isIntegerTy() && !lhs->getType()->isIntegerTy();
return rhs->getType()->getPrimitiveSizeInBits()
< lhs->getType()->getPrimitiveSizeInBits();
}
/// replaceCongruentIVs - Check for congruent phis in this loop header and
/// replace them with their most canonical representative. Return the number of
/// phis eliminated.
@ -1564,23 +1574,45 @@ bool SCEVExpander::hoistStep(Instruction *IncV, Instruction *InsertPos,
/// This does not depend on any SCEVExpander state but should be used in
/// the same context that SCEVExpander is used.
unsigned SCEVExpander::replaceCongruentIVs(Loop *L, const DominatorTree *DT,
SmallVectorImpl<WeakVH> &DeadInsts) {
SmallVectorImpl<WeakVH> &DeadInsts,
const TargetLowering *TLI) {
// Find integer phis in order of increasing width.
SmallVector<PHINode*, 8> Phis;
for (BasicBlock::iterator I = L->getHeader()->begin();
PHINode *Phi = dyn_cast<PHINode>(I); ++I) {
Phis.push_back(Phi);
}
if (TLI)
std::sort(Phis.begin(), Phis.end(), width_descending);
unsigned NumElim = 0;
DenseMap<const SCEV *, PHINode *> ExprToIVMap;
for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ++I) {
PHINode *Phi = cast<PHINode>(I);
// Process phis from wide to narrow. Mapping wide phis to the their truncation
// so narrow phis can reuse them.
for (SmallVectorImpl<PHINode*>::const_iterator PIter = Phis.begin(),
PEnd = Phis.end(); PIter != PEnd; ++PIter) {
PHINode *Phi = *PIter;
if (!SE.isSCEVable(Phi->getType()))
continue;
PHINode *&OrigPhiRef = ExprToIVMap[SE.getSCEV(Phi)];
if (!OrigPhiRef) {
OrigPhiRef = Phi;
if (Phi->getType()->isIntegerTy() && TLI
&& TLI->isTruncateFree(Phi->getType(), Phis.back()->getType())) {
// This phi can be freely truncated to the narrowest phi type. Map the
// truncated expression to it so it will be reused for narrow types.
const SCEV *TruncExpr =
SE.getTruncateExpr(SE.getSCEV(Phi), Phis.back()->getType());
ExprToIVMap[TruncExpr] = Phi;
}
continue;
}
// If one phi derives from the other via GEPs, types may differ.
// We could consider adding a bitcast here to handle it.
if (OrigPhiRef->getType() != Phi->getType())
// Replacing a pointer phi with an integer phi or vice-versa doesn't make
// sense.
if (OrigPhiRef->getType()->isPointerTy() != Phi->getType()->isPointerTy())
continue;
if (BasicBlock *LatchBlock = L->getLoopLatch()) {
@ -1589,8 +1621,10 @@ unsigned SCEVExpander::replaceCongruentIVs(Loop *L, const DominatorTree *DT,
Instruction *IsomorphicInc =
cast<Instruction>(Phi->getIncomingValueForBlock(LatchBlock));
// If this phi is more canonical, swap it with the original.
if (!isExpandedAddRecExprPHI(OrigPhiRef, OrigInc, L)
// If this phi has the same width but is more canonical, replace the
// original with it.
if (OrigPhiRef->getType() == Phi->getType()
&& !isExpandedAddRecExprPHI(OrigPhiRef, OrigInc, L)
&& isExpandedAddRecExprPHI(Phi, IsomorphicInc, L)) {
std::swap(OrigPhiRef, Phi);
std::swap(OrigInc, IsomorphicInc);
@ -1600,21 +1634,35 @@ unsigned SCEVExpander::replaceCongruentIVs(Loop *L, const DominatorTree *DT,
// that a phi is congruent, it's often the head of an IV user cycle that
// is isomorphic with the original phi. So it's worth eagerly cleaning up
// the common case of a single IV increment.
if (OrigInc != IsomorphicInc &&
OrigInc->getType() == IsomorphicInc->getType() &&
SE.getSCEV(OrigInc) == SE.getSCEV(IsomorphicInc) &&
const SCEV *TruncExpr = SE.getTruncateOrNoop(SE.getSCEV(OrigInc),
IsomorphicInc->getType());
if (OrigInc != IsomorphicInc
&& TruncExpr == SE.getSCEV(IsomorphicInc) &&
hoistStep(OrigInc, IsomorphicInc, DT)) {
DEBUG_WITH_TYPE(DebugType, dbgs()
<< "INDVARS: Eliminated congruent iv.inc: "
<< *IsomorphicInc << '\n');
IsomorphicInc->replaceAllUsesWith(OrigInc);
Value *NewInc = OrigInc;
if (OrigInc->getType() != IsomorphicInc->getType()) {
IRBuilder<> Builder(OrigInc->getNextNode());
Builder.SetCurrentDebugLocation(IsomorphicInc->getDebugLoc());
NewInc = Builder.
CreateTruncOrBitCast(OrigInc, IsomorphicInc->getType(), IVName);
}
IsomorphicInc->replaceAllUsesWith(NewInc);
DeadInsts.push_back(IsomorphicInc);
}
}
DEBUG_WITH_TYPE(DebugType, dbgs()
<< "INDVARS: Eliminated congruent iv: " << *Phi << '\n');
++NumElim;
Phi->replaceAllUsesWith(OrigPhiRef);
Value *NewIV = OrigPhiRef;
if (OrigPhiRef->getType() != Phi->getType()) {
IRBuilder<> Builder(L->getHeader()->getFirstInsertionPt());
Builder.SetCurrentDebugLocation(Phi->getDebugLoc());
NewIV = Builder.CreateTruncOrBitCast(OrigPhiRef, Phi->getType(), IVName);
}
Phi->replaceAllUsesWith(NewIV);
DeadInsts.push_back(Phi);
}
return NumElim;

4
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
View File

@ -3865,7 +3865,7 @@ LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
// Remove any extra phis created by processing inner loops.
SmallVector<WeakVH, 16> DeadInsts;
SCEVExpander Rewriter(SE, "lsr");
Changed |= (bool)Rewriter.replaceCongruentIVs(L, &DT, DeadInsts);
Changed |= (bool)Rewriter.replaceCongruentIVs(L, &DT, DeadInsts, TLI);
Changed |= (bool)DeleteTriviallyDeadInstructions(DeadInsts);
}
DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n");
@ -3918,7 +3918,7 @@ LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
// Remove any extra phis created by processing inner loops.
SmallVector<WeakVH, 16> DeadInsts;
SCEVExpander Rewriter(SE, "lsr");
Changed |= (bool)Rewriter.replaceCongruentIVs(L, &DT, DeadInsts);
Changed |= (bool)Rewriter.replaceCongruentIVs(L, &DT, DeadInsts, TLI);
Changed |= (bool)DeleteTriviallyDeadInstructions(DeadInsts);
}
}

4
llvm/test/Transforms/IndVarSimplify/no-iv-rewrite.ll
View File

@ -333,9 +333,9 @@ entry:
; CHECK: loop:
; CHECK: phi %structIF*
; CHECK: phi i32*
; CHECK: getelementptr inbounds
; CHECK-NOT: phi
; CHECK: getelementptr inbounds
; CHECK-NOT: getelementptr
; CHECK: exit:
loop:
%ptr.iv = phi %structIF* [ %ptr.inc, %latch ], [ %base, %entry ]