[PATCH] Fix PR22222
david.majnemer at gmail.com
Wed Jan 14 18:50:44 PST 2015
On Wednesday, January 14, 2015, Sanjoy Das <sanjoy at playingwithpointers.com>
> In http://reviews.llvm.org/D6979#108906, @majnemer wrote:
> > LGTM.
> > Out of curiosity, why isn't this implemented like the code here:
> In retrospect, that would have been the right way to do it. Directly
> checking zext(A + B) == zext(A) + zext(B) does not catch
> `test.unsigned.add.0` (in the test file), but I think that is fixable.
> Moreover, the approach you pointed out can be easily generalized to
> subtraction. I don't think you can easily generalize it to multiplication
> (since checking for `BitWidth + 1` may not be sufficient in that case); but
> we're not handling multiplication anyway.
Multiplication can be handled the same way but you must use bitwidth * 2
instead of bitwidth+1.
> I'll try to implement the approach `LinearFunctionTestReplace` and send in
> a patch for review sometime this week.
> rL LLVM
> EMAIL PREFERENCES
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