diff options
| -rw-r--r-- | lib/Analysis/ScalarEvolution.cpp | 19 | ||||
| -rw-r--r-- | test/Analysis/ScalarEvolution/max-trip-count.ll | 28 |
2 files changed, 43 insertions, 4 deletions
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index ea45e9d72c..f35f11615f 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -5119,7 +5119,7 @@ SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) { // Compute the two solutions for the quadratic formula. // The divisions must be performed as signed divisions. APInt NegB(-B); - APInt TwoA( A << 1 ); + APInt TwoA(A << 1); if (TwoA.isMinValue()) { const SCEV *CNC = SE.getCouldNotCompute(); return std::make_pair(CNC, CNC); @@ -5134,7 +5134,7 @@ SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) { return std::make_pair(SE.getConstant(Solution1), SE.getConstant(Solution2)); - } // end APIntOps namespace + } // end APIntOps namespace } /// HowFarToZero - Return the number of times a backedge comparing the specified @@ -5228,8 +5228,19 @@ ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L) { // Handle unitary steps, which cannot wraparound. // 1*N = -Start; -1*N = Start (mod 2^BW), so: // N = Distance (as unsigned) - if (StepC->getValue()->equalsInt(1) || StepC->getValue()->isAllOnesValue()) - return Distance; + if (StepC->getValue()->equalsInt(1) || StepC->getValue()->isAllOnesValue()) { + ConstantRange CR = getUnsignedRange(Start); + const SCEV *MaxBECount; + if (!CountDown && CR.getUnsignedMin().isMinValue()) + // When counting up, the worst starting value is 1, not 0. + MaxBECount = CR.getUnsignedMax().isMinValue() + ? getConstant(APInt::getMinValue(CR.getBitWidth())) + : getConstant(APInt::getMaxValue(CR.getBitWidth())); + else + MaxBECount = getConstant(CountDown ? CR.getUnsignedMax() + : -CR.getUnsignedMin()); + return ExitLimit(Distance, MaxBECount); + } // If the recurrence is known not to wraparound, unsigned divide computes the // back edge count. We know that the value will either become zero (and thus diff --git a/test/Analysis/ScalarEvolution/max-trip-count.ll b/test/Analysis/ScalarEvolution/max-trip-count.ll index 843fb07308..0cdbdf57a6 100644 --- a/test/Analysis/ScalarEvolution/max-trip-count.ll +++ b/test/Analysis/ScalarEvolution/max-trip-count.ll @@ -70,3 +70,31 @@ for.end: ; preds = %for.body, %for.cond } declare i32 @printf(i8*, ...) + +define void @test(i8* %a, i32 %n) nounwind { +entry: + %cmp1 = icmp sgt i32 %n, 0 + br i1 %cmp1, label %for.body.lr.ph, label %for.end + +for.body.lr.ph: ; preds = %entry + %tmp = zext i32 %n to i64 + br label %for.body + +for.body: ; preds = %for.body, %for.body.lr.ph + %indvar = phi i64 [ %indvar.next, %for.body ], [ 0, %for.body.lr.ph ] + %arrayidx = getelementptr i8* %a, i64 %indvar + store i8 0, i8* %arrayidx, align 1 + %indvar.next = add i64 %indvar, 1 + %exitcond = icmp ne i64 %indvar.next, %tmp + br i1 %exitcond, label %for.body, label %for.cond.for.end_crit_edge + +for.cond.for.end_crit_edge: ; preds = %for.body + br label %for.end + +for.end: ; preds = %for.cond.for.end_crit_edge, %entry + ret void +} + +; CHECK: Determining loop execution counts for: @test +; CHECK-NEXT: backedge-taken count is +; CHECK-NEXT: max backedge-taken count is -1 |