From 498cbaf867d6e5fa2c4a397318f0376dd7d6292c Mon Sep 17 00:00:00 2001
From: Bruno Cardoso Lopes <bruno.cardoso@gmail.com>
Date: Tue, 2 Dec 2014 14:22:34 +0000
Subject: [PATCH] [LICM] Avoind store sinking if no preheader is available

Load instructions are inserted into loop preheaders when sinking stores
and later removed if not used by the SSA updater. Avoid sinking if the
loop has no preheader and avoid crashes. This fixes one more side effect
of not handling indirectbr instructions properly on LoopSimplify.

llvm-svn: 223119
---
 lib/Transforms/Scalar/LICM.cpp  |  6 ++++--
 test/Transforms/LICM/sinking.ll | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/lib/Transforms/Scalar/LICM.cpp b/lib/Transforms/Scalar/LICM.cpp
index c706248267f..99725b5f738 100644
--- a/lib/Transforms/Scalar/LICM.cpp
+++ b/lib/Transforms/Scalar/LICM.cpp
@@ -847,8 +847,10 @@ void LICM::PromoteAliasSet(AliasSet &AS,
           return;
         // Don't sink stores from loops without dedicated block exits. Exits
         // containing indirect branches are not transformed by loop simplify,
-        // make sure we catch that.
-        if (!HasDedicatedExits)
+        // make sure we catch that. An additional load may be generated in the
+        // preheader for SSA updater, so also avoid sinking when no preheader
+        // is available.
+        if (!HasDedicatedExits || !Preheader)
           return;
 
         // Note that we only check GuaranteedToExecute inside the store case
diff --git a/test/Transforms/LICM/sinking.ll b/test/Transforms/LICM/sinking.ll
index f01367b01aa..d7a8fcdafca 100644
--- a/test/Transforms/LICM/sinking.ll
+++ b/test/Transforms/LICM/sinking.ll
@@ -359,6 +359,39 @@ lab22:
   indirectbr i8* undef, [label %lab5, label %lab6, label %lab7]
 }
 
+; Test that we don't crash when trying to sink stores and there's no preheader
+; available (which is used for creating loads that may be used by the SSA
+; updater)
+define void @test13() {
+; CHECK-LABEL: @test13
+  br label %lab59
+
+lab19:
+  br i1 undef, label %lab20, label %lab38
+
+lab20:
+  br label %lab60
+
+lab21:
+  br i1 undef, label %lab22, label %lab38
+
+lab22:
+  br label %lab38
+
+lab38:
+  ret void
+
+lab59:
+  indirectbr i8* undef, [label %lab60, label %lab38]
+
+lab60:
+; CHECK: lab60:
+; CHECK: store
+; CHECK-NEXT: indirectbr
+  store i32 2145244101, i32* undef, align 4
+  indirectbr i8* undef, [label %lab21, label %lab19]
+}
+
 declare void @f(i32*)
 
 declare void @g()