Merging r258184:

[oota-llvm.git] / lib / Analysis / ScalarEvolution.cpp

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 1ca72accc42e069338c730290b412f74cde3e212..ef1bb3a36c8d4205652560cfa9c04bf112c9e540 100644 (file)
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -5368,6 +5368,14 @@ ScalarEvolution::computeExitLimitFromCond(const Loop *L,
           BECount = EL0.Exact;
       }
 
+      // There are cases (e.g. PR26207) where computeExitLimitFromCond is able
+      // to be more aggressive when computing BECount than when computing
+      // MaxBECount.  In these cases it is possible for EL0.Exact and EL1.Exact
+      // to match, but for EL0.Max and EL1.Max to not.
+      if (isa<SCEVCouldNotCompute>(MaxBECount) &&
+          !isa<SCEVCouldNotCompute>(BECount))
+        MaxBECount = BECount;
+
       return ExitLimit(BECount, MaxBECount);
     }
     if (BO->getOpcode() == Instruction::Or) {
@@ -9439,23 +9447,22 @@ static void replaceSubString(std::string &Str, StringRef From, StringRef To) {
 /// getLoopBackedgeTakenCounts - Helper method for verifyAnalysis.
 static void
 getLoopBackedgeTakenCounts(Loop *L, VerifyMap &Map, ScalarEvolution &SE) {
-  for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I) {
-    getLoopBackedgeTakenCounts(*I, Map, SE); // recurse.
-
-    std::string &S = Map[L];
-    if (S.empty()) {
-      raw_string_ostream OS(S);
-      SE.getBackedgeTakenCount(L)->print(OS);
-
-      // false and 0 are semantically equivalent. This can happen in dead loops.
-      replaceSubString(OS.str(), "false", "0");
-      // Remove wrap flags, their use in SCEV is highly fragile.
-      // FIXME: Remove this when SCEV gets smarter about them.
-      replaceSubString(OS.str(), "<nw>", "");
-      replaceSubString(OS.str(), "<nsw>", "");
-      replaceSubString(OS.str(), "<nuw>", "");
-    }
-  }
+  std::string &S = Map[L];
+  if (S.empty()) {
+    raw_string_ostream OS(S);
+    SE.getBackedgeTakenCount(L)->print(OS);
+
+    // false and 0 are semantically equivalent. This can happen in dead loops.
+    replaceSubString(OS.str(), "false", "0");
+    // Remove wrap flags, their use in SCEV is highly fragile.
+    // FIXME: Remove this when SCEV gets smarter about them.
+    replaceSubString(OS.str(), "<nw>", "");
+    replaceSubString(OS.str(), "<nsw>", "");
+    replaceSubString(OS.str(), "<nuw>", "");
+  }
+
+  for (auto *R : reverse(*L))
+    getLoopBackedgeTakenCounts(R, Map, SE); // recurse.
 }
 
 void ScalarEvolution::verify() const {