[ScopDetect] Include zero-iteration loops in loop count.

Loop with zero iteration are, syntactically, loops. They have been
excluded from the loop counter even for the non-profitable counters.
This seems to be unintentially as the sentinel value of '0' minimal
iterations does exclude such loops.

Fix by never considering the iteration count when the sentinel
value of 0 is found.

This makes the recently added NumTotalLoops couter redundant
with NumLoopsOverall, which now is equivalent. Hence, NumTotalLoops
is removed as well.

Note: The test case 'ScopDetect/statistics.ll' effectively does not
check profitability, because -polly-process-unprofitable is passed
to all test cases.

llvm-svn: 311551

2 files changed, 41 insertions, 26 deletions

diff --git a/polly/lib/Analysis/ScopDetection.cpp b/polly/lib/Analysis/ScopDetection.cpp
index 02f515af13e..0db9c93be8c 100644
--- a/polly/lib/Analysis/ScopDetection.cpp
+++ b/polly/lib/Analysis/ScopDetection.cpp
@@ -212,8 +212,6 @@ StringRef polly::PollySkipFnAttr = "polly.skip.fn";
 //===----------------------------------------------------------------------===//
 // Statistics.
 
-STATISTIC(NumTotalLoops, "Number of loops (in- or out of scops, in any "
-                         "function processed by Polly)");
 STATISTIC(NumScopRegions, "Number of scops");
 STATISTIC(NumLoopsInScop, "Number of loops in scops");
 STATISTIC(NumScopsDepthOne, "Number of scops with maximal loop depth 1");
@@ -305,17 +303,6 @@ static bool doesStringMatchAnyRegex(StringRef Str,
 //===----------------------------------------------------------------------===//
 // ScopDetection.
 
-static void countTotalLoops(Loop *L) {
-  NumTotalLoops++;
-  for (Loop *SubLoop : L->getSubLoops())
-    countTotalLoops(SubLoop);
-}
-
-static void countTotalLoops(LoopInfo &LI) {
-  for (Loop *L : LI)
-    countTotalLoops(L);
-}
-
 ScopDetection::ScopDetection(Function &F, const DominatorTree &DT,
                              ScalarEvolution &SE, LoopInfo &LI, RegionInfo &RI,
                              AliasAnalysis &AA, OptimizationRemarkEmitter &ORE)
@@ -338,7 +325,6 @@ ScopDetection::ScopDetection(Function &F, const DominatorTree &DT,
 
   findScops(*TopRegion);
 
-  countTotalLoops(LI);
   NumScopRegions += ValidRegions.size();
 
   // Prune non-profitable regions.
@@ -1238,10 +1224,11 @@ ScopDetection::countBeneficialSubLoops(Loop *L, ScalarEvolution &SE,
 
   int NumLoops = 1;
   int MaxLoopDepth = 1;
-  if (auto *TripCountC = dyn_cast<SCEVConstant>(TripCount))
-    if (TripCountC->getType()->getScalarSizeInBits() <= 64)
-      if (TripCountC->getValue()->getZExtValue() <= MinProfitableTrips)
-        NumLoops -= 1;
+  if (MinProfitableTrips > 0)
+    if (auto *TripCountC = dyn_cast<SCEVConstant>(TripCount))
+      if (TripCountC->getType()->getScalarSizeInBits() <= 64)
+        if (TripCountC->getValue()->getZExtValue() <= MinProfitableTrips)
+          NumLoops -= 1;
 
   for (auto &SubLoop : *L) {
     LoopStats Stats = countBeneficialSubLoops(SubLoop, SE, MinProfitableTrips);
diff --git a/polly/test/ScopDetect/statistics.ll b/polly/test/ScopDetect/statistics.ll
index fbc91f4b24d..da78821c2ef 100644
--- a/polly/test/ScopDetect/statistics.ll
+++ b/polly/test/ScopDetect/statistics.ll
@@ -2,20 +2,19 @@
 
 ; REQUIRES: asserts
 
-; CHECK-DAG: 10 polly-detect     - Number of loops (in- or out of scops, in any function processed by Polly)
 ; CHECK-DAG:  4 polly-detect     - Maximal number of loops in scops (profitable scops only)
 ; CHECK-DAG:  4 polly-detect     - Maximal number of loops in scops
-; CHECK-DAG: 10 polly-detect     - Number of loops in scops (profitable scops only)
-; CHECK-DAG: 10 polly-detect     - Number of loops in scops
-; CHECK-DAG: 10 polly-detect     - Number of total loops
-; CHECK-DAG:  4 polly-detect     - Number of scops (profitable scops only)
+; CHECK-DAG: 11 polly-detect     - Number of loops in scops (profitable scops only)
+; CHECK-DAG: 11 polly-detect     - Number of loops in scops
+; CHECK-DAG: 11 polly-detect     - Number of total loops
+; CHECK-DAG:  5 polly-detect     - Number of scops (profitable scops only)
 ; CHECK-DAG:  1 polly-detect     - Number of scops with maximal loop depth 4 (profitable scops only)
-; CHECK-DAG:  1 polly-detect     - Number of scops with maximal loop depth 1 (profitable scops only)
+; CHECK-DAG:  2 polly-detect     - Number of scops with maximal loop depth 1 (profitable scops only)
 ; CHECK-DAG:  1 polly-detect     - Number of scops with maximal loop depth 3 (profitable scops only)
 ; CHECK-DAG:  1 polly-detect     - Number of scops with maximal loop depth 2 (profitable scops only)
-; CHECK-DAG:  4 polly-detect     - Number of scops
+; CHECK-DAG:  5 polly-detect     - Number of scops
 ; CHECK-DAG:  1 polly-detect     - Number of scops with maximal loop depth 4
-; CHECK-DAG:  1 polly-detect     - Number of scops with maximal loop depth 1
+; CHECK-DAG:  2 polly-detect     - Number of scops with maximal loop depth 1
 ; CHECK-DAG:  1 polly-detect     - Number of scops with maximal loop depth 3
 ; CHECK-DAG:  1 polly-detect     - Number of scops with maximal loop depth 2
 
@@ -45,6 +44,10 @@
 ;              A[i + j + k + l] += i + j + k + l;
 ;    }
 ;
+;    void foo_zero_iterations(float *S) {
+;      for (long i = 0; i < 0; i++)
+;        A[i] += i;
+;    }
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 define void @foo_1d(float* %A) {
@@ -248,3 +251,28 @@ bb30:                                             ; preds = %bb29
 bb32:                                             ; preds = %bb4
   ret void
 }
+
+define void @foo_zero_iterations(float* %A) {
+bb:
+  br label %bb1
+
+bb1:                                              ; preds = %bb6, %bb
+  %i.0 = phi i64 [ 0, %bb ], [ %tmp7, %bb6 ]
+  %exitcond = icmp ne i64 %i.0, 0
+  br i1 %exitcond, label %bb2, label %bb8
+
+bb2:                                              ; preds = %bb1
+  %tmp = sitofp i64 %i.0 to float
+  %tmp3 = getelementptr inbounds float, float* %A, i64 %i.0
+  %tmp4 = load float, float* %tmp3, align 4
+  %tmp5 = fadd float %tmp4, %tmp
+  store float %tmp5, float* %tmp3, align 4
+  br label %bb6
+
+bb6:                                              ; preds = %bb2
+  %tmp7 = add nuw nsw i64 %i.0, 1
+  br label %bb1
+
+bb8:                                              ; preds = %bb1
+  ret void
+}