From 28aff84ceb2fcf0e4b05ed95b81e46fcd4cd373f Mon Sep 17 00:00:00 2001
From: Benjamin Kramer <benny.kra@googlemail.com>
Date: Fri, 21 Sep 2012 17:27:23 +0000
Subject: [PATCH] LoopIdiom: Give up when the loop is not in canonical form.

We rely on it when doing the transforms. This can happen when there is an
indirectbr in  the loop.

Fixes PR13892.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164383 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/LoopIdiomRecognize.cpp  |  5 +++
 .../LoopIdiom/non-canonical-loop.ll           | 34 +++++++++++++++++++
 2 files changed, 39 insertions(+)
 create mode 100644 test/Transforms/LoopIdiom/non-canonical-loop.ll

diff --git a/lib/Transforms/Scalar/LoopIdiomRecognize.cpp b/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
index a72e288303f..1553328c07d 100644
--- a/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ b/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -175,6 +175,11 @@ static void deleteIfDeadInstruction(Value *V, ScalarEvolution &SE,
 bool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) {
   CurLoop = L;
 
+  // If the loop could not be converted to canonical form, it must have an
+  // indirectbr in it, just give up.
+  if (!L->getLoopPreheader())
+    return false;
+
   // Disable loop idiom recognition if the function's name is a common idiom.
   StringRef Name = L->getHeader()->getParent()->getName();
   if (Name == "memset" || Name == "memcpy")
diff --git a/test/Transforms/LoopIdiom/non-canonical-loop.ll b/test/Transforms/LoopIdiom/non-canonical-loop.ll
new file mode 100644
index 00000000000..a6a4f9227f9
--- /dev/null
+++ b/test/Transforms/LoopIdiom/non-canonical-loop.ll
@@ -0,0 +1,34 @@
+; RUN: opt -S -loop-idiom < %s
+; Don't crash
+; PR13892
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @test(i32* %currMB) nounwind uwtable {
+entry:
+  br i1 undef, label %start.exit, label %if.then.i
+
+if.then.i:                                        ; preds = %entry
+  unreachable
+
+start.exit:                       ; preds = %entry
+  indirectbr i8* undef, [label %0, label %for.bodyprime]
+
+; <label>:0                                       ; preds = %start.exit
+  unreachable
+
+for.bodyprime:                                    ; preds = %for.bodyprime, %start.exit
+  %i.057375 = phi i32 [ 0, %start.exit ], [ %1, %for.bodyprime ]
+  %arrayidx8prime = getelementptr inbounds i32* %currMB, i32 %i.057375
+  store i32 0, i32* %arrayidx8prime, align 4
+  %1 = add i32 %i.057375, 1
+  %cmp5prime = icmp slt i32 %1, 4
+  br i1 %cmp5prime, label %for.bodyprime, label %for.endprime
+
+for.endprime:                                     ; preds = %for.bodyprime
+  br label %for.body23prime
+
+for.body23prime:                                  ; preds = %for.body23prime, %for.endprime
+  br label %for.body23prime
+}
-- 
2.34.1