Add a note.

llvm-svn: 118337

lib/Target/README.txt

@@ -1963,3 +1963,15 @@ bb3:            ; preds = %entry
         ret i32 %b
 }
 //===---------------------------------------------------------------------===//
+We should fold this code into "ret i1 false" since neither %zero nor %one can
+ever be null pointers.
+
+define i1 @foo(i1 %cond) {
+  %zero = alloca i32
+  %one = alloca i32
+
+  %ptr = select i1 %cond, i32* %zero, i32* %one
+  %isnull = icmp eq i32* %ptr, null
+  ret i1 %isnull
+}
+//===---------------------------------------------------------------------===//