From 2a7fbb1927153390dd2f04958f79c2ecca11b87e Mon Sep 17 00:00:00 2001
From: James Molloy <james.molloy@arm.com>
Date: Mon, 16 Feb 2015 17:02:00 +0000
Subject: [PATCH] [LoopReroll] Relax some assumptions a little.

We won't find a root with index zero in any loop that we are able to reroll.
However, we may find one in a non-rerollable loop, so bail gracefully instead
of failing hard.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229406 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/LoopRerollPass.cpp |  9 ++++---
 test/Transforms/LoopReroll/basic.ll      | 30 ++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/lib/Transforms/Scalar/LoopRerollPass.cpp b/lib/Transforms/Scalar/LoopRerollPass.cpp
index 704299f3041..fdf7e3b1b19 100644
--- a/lib/Transforms/Scalar/LoopRerollPass.cpp
+++ b/lib/Transforms/Scalar/LoopRerollPass.cpp
@@ -719,14 +719,17 @@ collectPossibleRoots(Instruction *Base, std::map<int64_t,Instruction*> &Roots) {
 
   if (Roots.empty())
     return false;
-  
-  assert(Roots.find(0) == Roots.end() && "Didn't expect a zero index!");
 
   // If we found non-loop-inc, non-root users of Base, assume they are
   // for the zeroth root index. This is because "add %a, 0" gets optimized
   // away.
-  if (BaseUsers.size())
+  if (BaseUsers.size()) {
+    if (Roots.find(0) != Roots.end()) {
+      DEBUG(dbgs() << "LRR: Multiple roots found for base - aborting!\n");
+      return false;
+    }
     Roots[0] = Base;
+  }
 
   // Calculate the number of users of the base, or lowest indexed, iteration.
   unsigned NumBaseUses = BaseUsers.size();
diff --git a/test/Transforms/LoopReroll/basic.ll b/test/Transforms/LoopReroll/basic.ll
index f30f417f17a..75334611d5f 100644
--- a/test/Transforms/LoopReroll/basic.ll
+++ b/test/Transforms/LoopReroll/basic.ll
@@ -545,6 +545,36 @@ for.end:                                          ; preds = %for.body
   ret void
 }
 
+%struct.s = type { i32, i32 }
+
+; Function Attrs: nounwind uwtable
+define void @gep1(%struct.s* nocapture %x) #0 {
+entry:
+  %call = tail call i32 @foo(i32 0) #1
+  br label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %0 = mul nsw i64 %indvars.iv, 3
+  %arrayidx = getelementptr inbounds %struct.s* %x, i64 %0, i32 0
+  store i32 %call, i32* %arrayidx, align 4
+  %1 = add nsw i64 %0, 1
+  %arrayidx4 = getelementptr inbounds %struct.s* %x, i64 %1, i32 0
+  store i32 %call, i32* %arrayidx4, align 4
+  %2 = add nsw i64 %0, 2
+  %arrayidx9 = getelementptr inbounds %struct.s* %x, i64 %2, i32 0
+  store i32 %call, i32* %arrayidx9, align 4
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %exitcond = icmp eq i64 %indvars.iv.next, 500
+  br i1 %exitcond, label %for.end, label %for.body
+
+; CHECK-LABEL: @gep1
+; This test is a crash test only.
+; CHECK: ret
+for.end:                                          ; preds = %for.body
+  ret void
+}
+
 
 attributes #0 = { nounwind uwtable }
 attributes #1 = { nounwind }
-- 
2.34.1