RewriteLoopBodyWithConditionConstant can end up rewriting the

condition we're unswitching on.  In this case, don't try to
simplify the second copy of the loop which may be dead or not,
but is probably a constant now.  This fixes PR6879


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101870 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/LoopUnswitch/crash.ll

@@ -45,3 +45,22 @@ for.body:                                         ; preds = %for.body, %bb.nph
 for.end:                                          ; preds = %for.body, %entry
   ret void
 }
+
+; PR6879
+define i32* @test3(i32** %p_45, i16 zeroext %p_46, i64 %p_47, i64 %p_48, i16 signext %p_49) nounwind {
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.cond4, %entry
+  br i1 false, label %for.cond4, label %for.end88
+
+for.cond4:                                        ; preds = %for.cond
+  %conv46 = trunc i32 0 to i8                     ; <i8> [#uses=2]
+  %cmp60 = icmp sgt i8 %conv46, 124               ; <i1> [#uses=1]
+  %or.cond = and i1 undef, %cmp60                 ; <i1> [#uses=1]
+  %cond = select i1 %or.cond, i8 %conv46, i8 undef ; <i8> [#uses=0]
+  br label %for.cond
+
+for.end88:                                        ; preds = %for.cond
+  ret i32* undef
+}