From 3a7d55b623752dbef21258409ec120cd4e70410f Mon Sep 17 00:00:00 2001
From: Michael Zolotukhin <mzolotukhin@apple.com>
Date: Wed, 29 Jul 2015 18:10:29 +0000
Subject: [PATCH] [Unroll] Don't crash when simplified branch condition is
 undef.

llvm-svn: 243544
---
 llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp      | 18 ++++++++++++----
 .../Transforms/LoopUnroll/full-unroll-crashers.ll  | 25 ++++++++++++++++++++++
 2 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
index 159ed20..25b0877 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -599,8 +599,13 @@ analyzeLoopUnrollCost(const Loop *L, unsigned TripCount, ScalarEvolution &SE,
         if (BI->isConditional()) {
           if (Constant *SimpleCond =
                   SimplifiedValues.lookup(BI->getCondition())) {
-            BasicBlock *Succ = BI->getSuccessor(
-                cast<ConstantInt>(SimpleCond)->isZero() ? 1 : 0);
+            BasicBlock *Succ = nullptr;
+            // Just take the first successor if condition is undef
+            if (isa<UndefValue>(SimpleCond))
+              Succ = BI->getSuccessor(0);
+            else
+              Succ = BI->getSuccessor(
+                  cast<ConstantInt>(SimpleCond)->isZero() ? 1 : 0);
             if (L->contains(Succ))
               BBWorklist.insert(Succ);
             continue;
@@ -609,8 +614,13 @@ analyzeLoopUnrollCost(const Loop *L, unsigned TripCount, ScalarEvolution &SE,
       } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
         if (Constant *SimpleCond =
                 SimplifiedValues.lookup(SI->getCondition())) {
-          BasicBlock *Succ =
-              SI->getSuccessor(cast<ConstantInt>(SimpleCond)->getSExtValue());
+          BasicBlock *Succ = nullptr;
+          // Just take the first successor if condition is undef
+          if (isa<UndefValue>(SimpleCond))
+            Succ = SI->getSuccessor(0);
+          else
+            Succ =
+                SI->getSuccessor(cast<ConstantInt>(SimpleCond)->getSExtValue());
           if (L->contains(Succ))
             BBWorklist.insert(Succ);
           continue;
diff --git a/llvm/test/Transforms/LoopUnroll/full-unroll-crashers.ll b/llvm/test/Transforms/LoopUnroll/full-unroll-crashers.ll
index ac81452..0bf1327 100644
--- a/llvm/test/Transforms/LoopUnroll/full-unroll-crashers.ll
+++ b/llvm/test/Transforms/LoopUnroll/full-unroll-crashers.ll
@@ -2,6 +2,8 @@
 ; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=1000 -unroll-threshold=10 -unroll-percent-dynamic-cost-saved-threshold=20 -o /dev/null
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 
+@known_constant = internal unnamed_addr constant [10 x i32] [i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1], align 16
+
 define void @foo1() {
 entry:
   br label %for.body
@@ -32,3 +34,26 @@ for.body:
 for.exit:
   ret void
 }
+
+define void @cmp_undef() {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.inc, %entry
+  %iv.0 = phi i64 [ 0, %entry ], [ %iv.1, %for.inc ]
+  %arrayidx1 = getelementptr inbounds [10 x i32], [10 x i32]* @known_constant, i64 0, i64 %iv.0
+  %x1 = load i32, i32* %arrayidx1, align 4
+  %cmp = icmp eq i32 %x1, undef
+  br i1 %cmp, label %if.then, label %for.inc
+
+if.then:                                          ; preds = %for.body
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body, %if.then
+  %iv.1 = add nuw nsw i64 %iv.0, 1
+  %exitcond = icmp eq i64 %iv.1, 10
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.inc
+  ret void
+}
-- 
2.7.4