[Unroll] Don't crash when simplified branch condition is undef.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243544 91177308-0d34-0410-b5e6-96231b3b80d8

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
+}