2 files changed, 54 insertions, 12 deletions
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index dad8e07dad..d27afb09cf 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -6135,18 +6135,30 @@ bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
 
   // If LHS or RHS is an addrec, check to see if the condition is true in
   // every iteration of the loop.
-  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
-    if (isLoopEntryGuardedByCond(
-          AR->getLoop(), Pred, AR->getStart(), RHS) &&
-        isLoopBackedgeGuardedByCond(
-          AR->getLoop(), Pred, AR->getPostIncExpr(*this), RHS))
-      return true;
-  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS))
-    if (isLoopEntryGuardedByCond(
-          AR->getLoop(), Pred, LHS, AR->getStart()) &&
-        isLoopBackedgeGuardedByCond(
-          AR->getLoop(), Pred, LHS, AR->getPostIncExpr(*this)))
-      return true;
+  // If LHS and RHS are both addrec, both conditions must be true in
+  // every iteration of the loop.
+  const SCEVAddRecExpr *LAR = dyn_cast<SCEVAddRecExpr>(LHS);
+  const SCEVAddRecExpr *RAR = dyn_cast<SCEVAddRecExpr>(RHS);
+  bool LeftGuarded = false;
+  bool RightGuarded = false;
+  if (LAR) {
+    const Loop *L = LAR->getLoop();
+    if (isLoopEntryGuardedByCond(L, Pred, LAR->getStart(), RHS) &&
+        isLoopBackedgeGuardedByCond(L, Pred, LAR->getPostIncExpr(*this), RHS)) {
+      if (!RAR) return true;
+      LeftGuarded = true;
+    }
+  }
+  if (RAR) {
+    const Loop *L = RAR->getLoop();
+    if (isLoopEntryGuardedByCond(L, Pred, LHS, RAR->getStart()) &&
+        isLoopBackedgeGuardedByCond(L, Pred, LHS, RAR->getPostIncExpr(*this))) {
+      if (!LAR) return true;
+      RightGuarded = true;
+    }
+  }
+  if (LeftGuarded && RightGuarded)
+    return true;
 
   // Otherwise see what can be done with known constant ranges.
   return isKnownPredicateWithRanges(Pred, LHS, RHS);
diff --git a/test/Transforms/IndVarSimplify/pr18223.ll b/test/Transforms/IndVarSimplify/pr18223.ll
new file mode 100644
index 0000000000..738f75c0fe
--- /dev/null
+++ b/test/Transforms/IndVarSimplify/pr18223.ll
@@ -0,0 +1,30 @@
+; RUN: opt -indvars -S < %s | FileCheck %s
+
+; indvars should transform the phi node pair from the for-loop
+; CHECK-LABEL: @main(
+; CHECK: ret = phi i32 [ 0, %entry ], [ 0, {{.*}} ]
+
+@c = common global i32 0, align 4
+
+define i32 @main() #0 {
+entry:
+  %0 = load i32* @c, align 4
+  %tobool = icmp eq i32 %0, 0
+  br i1 %tobool, label %for.body, label %exit
+
+for.body:
+  %inc2 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
+  %sub = add i32 %inc2, -1
+  %cmp1 = icmp uge i32 %sub, %inc2
+  %conv = zext i1 %cmp1 to i32
+  br label %for.inc
+
+for.inc:
+  %inc = add nsw i32 %inc2, 1
+  %cmp = icmp slt i32 %inc, 5
+  br i1 %cmp, label %for.body, label %exit
+
+exit:
+  %ret = phi i32 [ 0, %entry ], [ %conv, %for.inc ]
+  ret i32 %ret
+}