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Handle decrementing loops properly. Fixes PR1533.
Always pass the constant as the second parameter to HowManyLessThans. Remove obsolete "isSigned" parameter. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@39893 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -475,10 +475,8 @@ namespace llvm {
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/// looking at this is that it returns the first iteration number where the
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/// value is not in the condition, thus computing the exit count. If the
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/// iteration count can't be computed, an instance of SCEVCouldNotCompute is
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/// returned. The isSigned parameter indicates whether the ConstantRange
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/// should be treated as signed or unsigned.
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SCEVHandle getNumIterationsInRange(ConstantRange Range,
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bool isSigned) const;
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/// returned.
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SCEVHandle getNumIterationsInRange(ConstantRange Range) const;
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SCEVHandle replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym,
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const SCEVHandle &Conc) const;
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@ -1671,8 +1671,7 @@ SCEVHandle ScalarEvolutionsImpl::ComputeIterationCount(const Loop *L) {
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ConstantRange CompRange(
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ICmpInst::makeConstantRange(Cond, CompVal->getValue()));
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SCEVHandle Ret = AddRec->getNumIterationsInRange(CompRange,
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false /*Always treat as unsigned range*/);
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SCEVHandle Ret = AddRec->getNumIterationsInRange(CompRange);
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if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
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}
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}
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@ -1696,7 +1695,8 @@ SCEVHandle ScalarEvolutionsImpl::ComputeIterationCount(const Loop *L) {
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break;
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}
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case ICmpInst::ICMP_SGT: {
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SCEVHandle TC = HowManyLessThans(RHS, LHS, L);
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SCEVHandle TC = HowManyLessThans(SCEV::getNegativeSCEV(LHS),
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SCEV::getNegativeSCEV(RHS), L);
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if (!isa<SCEVCouldNotCompute>(TC)) return TC;
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break;
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}
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@ -2406,8 +2406,7 @@ HowManyLessThans(SCEV *LHS, SCEV *RHS, const Loop *L) {
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/// this is that it returns the first iteration number where the value is not in
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/// the condition, thus computing the exit count. If the iteration count can't
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/// be computed, an instance of SCEVCouldNotCompute is returned.
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SCEVHandle SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
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bool isSigned) const {
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SCEVHandle SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range) const {
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if (Range.isFullSet()) // Infinite loop.
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return new SCEVCouldNotCompute();
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@ -2419,7 +2418,7 @@ SCEVHandle SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
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SCEVHandle Shifted = SCEVAddRecExpr::get(Operands, getLoop());
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if (SCEVAddRecExpr *ShiftedAddRec = dyn_cast<SCEVAddRecExpr>(Shifted))
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return ShiftedAddRec->getNumIterationsInRange(
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Range.subtract(SC->getValue()->getValue()),isSigned);
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Range.subtract(SC->getValue()->getValue()));
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// This is strange and shouldn't happen.
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return new SCEVCouldNotCompute();
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}
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@ -2443,17 +2442,16 @@ SCEVHandle SCEVAddRecExpr::getNumIterationsInRange(ConstantRange Range,
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// If this is an affine expression then we have this situation:
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// Solve {0,+,A} in Range === Ax in Range
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// Since we know that zero is in the range, we know that the upper value of
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// the range must be the first possible exit value. Also note that we
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// already checked for a full range.
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const APInt &Upper = Range.getUpper();
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APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
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// We know that zero is in the range. If A is positive then we know that
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// the upper value of the range must be the first possible exit value.
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// If A is negative then the lower of the range is the last possible loop
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// value. Also note that we already checked for a full range.
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APInt One(getBitWidth(),1);
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APInt A = cast<SCEVConstant>(getOperand(1))->getValue()->getValue();
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APInt End = A.sge(One) ? (Range.getUpper() - One) : Range.getLower();
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// The exit value should be (Upper+A-1)/A.
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APInt ExitVal(Upper);
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if (A != One)
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ExitVal = (Upper + A - One).sdiv(A);
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// The exit value should be (End+A)/A.
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APInt ExitVal = (End + A).sdiv(A);
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ConstantInt *ExitValue = ConstantInt::get(ExitVal);
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// Evaluate at the exit value. If we really did fall out of the valid
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20
test/Analysis/ScalarEvolution/2007-07-15-NegativeStride.ll
Normal file
20
test/Analysis/ScalarEvolution/2007-07-15-NegativeStride.ll
Normal file
@ -0,0 +1,20 @@
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; RUN: llvm-as < %s | opt -analyze -scalar-evolution 2>&1 | grep "Loop bb: 100 iterations"
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; PR1533
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@array = weak global [101 x i32] zeroinitializer, align 32 ; <[100 x i32]*> [#uses=1]
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define void @loop(i32 %x) {
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entry:
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br label %bb
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bb: ; preds = %bb, %entry
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%i.01.0 = phi i32 [ 100, %entry ], [ %tmp4, %bb ] ; <i32> [#uses=2]
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%tmp1 = getelementptr [101 x i32]* @array, i32 0, i32 %i.01.0 ; <i32*> [#uses=1]
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store i32 %x, i32* %tmp1
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%tmp4 = add i32 %i.01.0, -1 ; <i32> [#uses=2]
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%tmp7 = icmp sgt i32 %tmp4, -1 ; <i1> [#uses=1]
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br i1 %tmp7, label %bb, label %return
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return: ; preds = %bb
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ret void
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}
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