Add some simplifications for demanded bits, this allows instcombine to turn:

define i64 @test(i64 %A, i32 %B) {
        %tmp12 = zext i32 %B to i64             ; <i64> [#uses=1]
        %tmp3 = shl i64 %tmp12, 32              ; <i64> [#uses=1]
        %tmp5 = add i64 %tmp3, %A               ; <i64> [#uses=1]
        %tmp6 = and i64 %tmp5, 123              ; <i64> [#uses=1]
        ret i64 %tmp6
}

into:

define i64 @test(i64 %A, i32 %B) {
        %tmp6 = and i64 %A, 123         ; <i64> [#uses=1]
        ret i64 %tmp6
}

This implements Transforms/InstCombine/add2.ll:test1

llvm-svn: 34919