|  | ; RUN: llc < %s -mtriple=i386-apple-darwin -O0 | 
|  |  | 
|  | define fastcc void @optimize_bit_field() nounwind { | 
|  | bb4: | 
|  | %a = load i32* null             ; <i32> [#uses=1] | 
|  | %s = load i32* getelementptr (i32* null, i32 1)         ; <i32> [#uses=1] | 
|  | %z = load i32* getelementptr (i32* null, i32 2)         ; <i32> [#uses=1] | 
|  | %r = bitcast i32 0 to i32          ; <i32> [#uses=1] | 
|  | %q = trunc i32 %z to i8            ; <i8> [#uses=1] | 
|  | %b = icmp eq i8 0, %q              ; <i1> [#uses=1] | 
|  | br i1 %b, label %bb73, label %bb72 | 
|  |  | 
|  | bb72:      ; preds = %bb4 | 
|  | %f = tail call fastcc i32 @gen_lowpart(i32 %r, i32 %a) nounwind              ; <i32> [#uses=1] | 
|  | br label %bb73 | 
|  |  | 
|  | bb73:         ; preds = %bb72, %bb4 | 
|  | %y = phi i32 [ %f, %bb72 ], [ %s, %bb4 ]          ; <i32> [#uses=1] | 
|  | store i32 %y, i32* getelementptr (i32* null, i32 3) | 
|  | unreachable | 
|  | } | 
|  |  | 
|  | declare fastcc i32 @gen_lowpart(i32, i32) nounwind |