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Reapply 54786. Add overflow and number of mantissa bits checks.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54821 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel 2008-08-15 21:21:34 +00:00
parent cd1dcbd4fb
commit 35115f92e4
2 changed files with 217 additions and 1 deletions
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119
lib/Transforms/Scalar/LoopStrengthReduce.cpp
View File

@ -45,6 +45,7 @@ STATISTIC(NumReduced , "Number of GEPs strength reduced");
STATISTIC(NumInserted, "Number of PHIs inserted");
STATISTIC(NumVariable, "Number of PHIs with variable strides");
STATISTIC(NumEliminated , "Number of strides eliminated");
STATISTIC(NumShadow , "Number of Shadow IVs optimized");
namespace {
@ -177,8 +178,13 @@ private:
IVStrideUse* &CondUse,
const SCEVHandle* &CondStride);
void OptimizeIndvars(Loop *L);
/// OptimizeShadowIV - If IV is used in a int-to-float cast
/// inside the loop then try to eliminate the cast opeation.
void OptimizeShadowIV(Loop *L, ICmpInst *Cond,
const SCEVHandle *&CondStride);
bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse,
const SCEVHandle *&CondStride);
const SCEVHandle *&CondStride);
bool RequiresTypeConversion(const Type *Ty, const Type *NewTy);
unsigned CheckForIVReuse(bool, bool, const SCEVHandle&,
IVExpr&, const Type*,
@ -1689,6 +1695,115 @@ ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
return Cond;
}
/// OptimizeShadowIV - If IV is used in a int-to-float cast
/// inside the loop then try to eliminate the cast opeation.
void LoopStrengthReduce::OptimizeShadowIV(Loop *L, ICmpInst *Cond,
const SCEVHandle *&CondStride) {
const SCEVConstant *SC = dyn_cast<SCEVConstant>(*CondStride);
if (!SC) return;
SCEVHandle IterationCount = SE->getIterationCount(L);
if (isa<SCEVCouldNotCompute>(IterationCount))
return;
for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e;
++Stride) {
std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
IVUsesByStride.find(StrideOrder[Stride]);
assert(SI != IVUsesByStride.end() && "Stride doesn't exist!");
for (std::vector<IVStrideUse>::iterator UI = SI->second.Users.begin(),
E = SI->second.Users.end(); UI != E; /* empty */) {
std::vector<IVStrideUse>::iterator CandidateUI = UI;
UI++;
Instruction *ShadowUse = CandidateUI->User;
const Type *DestTy = NULL;
/* If shadow use is a int->float cast then insert a second IV
to elminate this cast.
for (unsigned i = 0; i < n; ++i)
foo((double)i);
is trnasformed into
double d = 0.0;
for (unsigned i = 0; i < n; ++i, ++d)
foo(d);
*/
UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->User);
if (UCast)
DestTy = UCast->getDestTy();
else {
SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->User);
if (!SCast) continue;
DestTy = SCast->getDestTy();
}
PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
if (!PH) continue;
if (PH->getNumIncomingValues() != 2) continue;
const Type *SrcTy = PH->getType();
int Mantissa = DestTy->getFPMantissaWidth();
if (Mantissa == -1) continue;
if ((int)TD->getTypeSizeInBits(SrcTy) > Mantissa)
continue;
unsigned Entry, Latch;
if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
Entry = 0;
Latch = 1;
} else {
Entry = 1;
Latch = 0;
}
ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
if (!Init) continue;
ConstantFP *NewInit = ConstantFP::get(DestTy, Init->getZExtValue());
BinaryOperator *Incr =
dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
if (!Incr) continue;
if (Incr->getOpcode() != Instruction::Add
&& Incr->getOpcode() != Instruction::Sub)
continue;
/* Initialize new IV, double d = 0.0 in above example. */
ConstantInt *C = NULL;
if (Incr->getOperand(0) == PH)
C = dyn_cast<ConstantInt>(Incr->getOperand(1));
else if (Incr->getOperand(1) == PH)
C = dyn_cast<ConstantInt>(Incr->getOperand(0));
else
continue;
if (!C) continue;
/* Add new PHINode. */
PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH);
/* create new icnrement. '++d' in above example. */
ConstantFP *CFP = ConstantFP::get(DestTy, C->getZExtValue());
BinaryOperator *NewIncr =
BinaryOperator::Create(Incr->getOpcode(),
NewPH, CFP, "IV.S.next.", Incr);
NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
/* Remove cast operation */
ShadowUse->replaceAllUsesWith(NewPH);
ShadowUse->eraseFromParent();
SI->second.Users.erase(CandidateUI);
NumShadow++;
break;
}
}
}
// OptimizeIndvars - Now that IVUsesByStride is set up with all of the indvar
// uses in the loop, look to see if we can eliminate some, in favor of using
// common indvars for the different uses.
@ -1716,6 +1831,8 @@ void LoopStrengthReduce::OptimizeIndvars(Loop *L) {
if (!FindIVUserForCond(Cond, CondUse, CondStride))
return; // setcc doesn't use the IV.
OptimizeShadowIV(L, Cond, CondStride);
// If possible, change stride and operands of the compare instruction to
// eliminate one stride.
Cond = ChangeCompareStride(L, Cond, CondUse, CondStride);

99
test/Transforms/LoopStrengthReduce/2008-08-14-ShadowIV.ll
View File

@ -0,0 +1,99 @@
; RUN: llvm-as < %s | opt -loop-reduce | llvm-dis | grep "phi double" | count 1
define void @foobar(i32 %n) nounwind {
entry:
icmp eq i32 %n, 0 ; <i1>:0 [#uses=2]
br i1 %0, label %return, label %bb.nph
bb.nph: ; preds = %entry
%umax = select i1 %0, i32 1, i32 %n ; <i32> [#uses=1]
br label %bb
bb: ; preds = %bb, %bb.nph
%i.03 = phi i32 [ 0, %bb.nph ], [ %indvar.next, %bb ] ; <i32> [#uses=3]
tail call void @bar( i32 %i.03 ) nounwind
uitofp i32 %i.03 to double ; <double>:1 [#uses=1]
tail call void @foo( double %1 ) nounwind
%indvar.next = add i32 %i.03, 1 ; <i32> [#uses=2]
%exitcond = icmp eq i32 %indvar.next, %umax ; <i1> [#uses=1]
br i1 %exitcond, label %return, label %bb
return: ; preds = %bb, %entry
ret void
}
; Unable to eliminate cast because the mantissa bits for double are not enough
; to hold all of i64 IV bits.
define void @foobar2(i64 %n) nounwind {
entry:
icmp eq i64 %n, 0 ; <i1>:0 [#uses=2]
br i1 %0, label %return, label %bb.nph
bb.nph: ; preds = %entry
%umax = select i1 %0, i64 1, i64 %n ; <i64> [#uses=1]
br label %bb
bb: ; preds = %bb, %bb.nph
%i.03 = phi i64 [ 0, %bb.nph ], [ %indvar.next, %bb ] ; <i64> [#uses=3]
trunc i64 %i.03 to i32 ; <i32>:1 [#uses=1]
tail call void @bar( i32 %1 ) nounwind
uitofp i64 %i.03 to double ; <double>:2 [#uses=1]
tail call void @foo( double %2 ) nounwind
%indvar.next = add i64 %i.03, 1 ; <i64> [#uses=2]
%exitcond = icmp eq i64 %indvar.next, %umax ; <i1> [#uses=1]
br i1 %exitcond, label %return, label %bb
return: ; preds = %bb, %entry
ret void
}
; Unable to eliminate cast due to potentional overflow.
define void @foobar3() nounwind {
entry:
tail call i32 (...)* @nn( ) nounwind ; <i32>:0 [#uses=1]
icmp eq i32 %0, 0 ; <i1>:1 [#uses=1]
br i1 %1, label %return, label %bb
bb: ; preds = %bb, %entry
%i.03 = phi i32 [ 0, %entry ], [ %3, %bb ] ; <i32> [#uses=3]
tail call void @bar( i32 %i.03 ) nounwind
uitofp i32 %i.03 to double ; <double>:2 [#uses=1]
tail call void @foo( double %2 ) nounwind
add i32 %i.03, 1 ; <i32>:3 [#uses=2]
tail call i32 (...)* @nn( ) nounwind ; <i32>:4 [#uses=1]
icmp ugt i32 %4, %3 ; <i1>:5 [#uses=1]
br i1 %5, label %bb, label %return
return: ; preds = %bb, %entry
ret void
}
; Unable to eliminate cast due to overflow.
define void @foobar4() nounwind {
entry:
br label %bb.nph
bb.nph: ; preds = %entry
br label %bb
bb: ; preds = %bb, %bb.nph
%i.03 = phi i8 [ 0, %bb.nph ], [ %indvar.next, %bb ] ; <i32> [#uses=3]
%tmp2 = sext i8 %i.03 to i32 ; <i32>:0 [#uses=1]
tail call void @bar( i32 %tmp2 ) nounwind
%tmp3 = uitofp i8 %i.03 to double ; <double>:1 [#uses=1]
tail call void @foo( double %tmp3 ) nounwind
%indvar.next = add i8 %i.03, 1 ; <i32> [#uses=2]
%tmp = sext i8 %indvar.next to i32
%exitcond = icmp eq i32 %tmp, 32767 ; <i1> [#uses=1]
br i1 %exitcond, label %return, label %bb
return: ; preds = %bb, %entry
ret void
}
declare void @bar(i32)
declare void @foo(double)
declare i32 @nn(...)