[llvm-commits] [PATCH] Simplify negated bit test

[David Majnemer]

Updated patch attached. No functional change, just nicer whitespace.


On Sat, Dec 8, 2012 at 3:53 PM, David Majnemer <david.majnemer at gmail.com>wrote:

> The attached patched takes a sequence like:
>  %neg = xor i32 %A, -1
>  %shl = shl i32 1, %B
>  %and = and i32 %shl, %neg
>  %cmp = icmp ne i32 %and, 0
>
> and turns it into:
>  %shl = shl i32 1, %B
>  %and = and i32 %shl, %A
>  %cmp = icmp eq i32 %and, 0
>
> The patch includes a test case that exercises this transform.
>
> Examples of frontend code that could generate sequence 1 is:
>
> bool fun1(unsigned A, unsigned B) { return ~A & (1 << B); }
>
> An example of sequence 2 is:
> bool fun2(unsigned A, unsigned B) { return !(A & (1 << B)); }
>
> With this patch, they would have the same IR.
>
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