[llvm] r275297 - add test for zexty xor sandwich

[Sanjay Patel via llvm-commits]

Sure. The general theme is that casts of all flavors interfere with all
optimizations. Is the solution to use ValueTracking (computeKnownBits, etc)
more liberally than pattern matching?

On Wed, Jul 13, 2016 at 1:23 PM, Eli Friedman <eli.friedman at gmail.com>
wrote:

> On Wed, Jul 13, 2016 at 11:40 AM, Sanjay Patel via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Author: spatel
>> Date: Wed Jul 13 13:40:38 2016
>> New Revision: 275297
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=275297&view=rev
>> Log:
>> add test for zexty xor sandwich
>>
>> Modified:
>>     llvm/trunk/test/Transforms/InstCombine/xor.ll
>>
>> Modified: llvm/trunk/test/Transforms/InstCombine/xor.ll
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/xor.ll?rev=275297&r1=275296&r2=275297&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/test/Transforms/InstCombine/xor.ll (original)
>> +++ llvm/trunk/test/Transforms/InstCombine/xor.ll Wed Jul 13 13:40:38 2016
>> @@ -242,6 +242,20 @@ define i32 @test22(i1 %X) {
>>    ret i32 %Q
>>  }
>>
>> +; Look through a zext between xors.
>> +
>> +define i32 @fold_zext_xor_sandwich(i1 %X) {
>> +; CHECK-LABEL: @fold_zext_xor_sandwich(
>> +; CHECK-NEXT:    [[TMP1:%.*]] = zext i1 %X to i32
>> +; CHECK-NEXT:    [[Q:%.*]] = xor i32 [[TMP1]], 3
>> +; CHECK-NEXT:    ret i32 [[Q]]
>> +;
>> +  %Y = xor i1 %X, true
>> +  %Z = zext i1 %Y to i32
>> +  %Q = xor i32 %Z, 2
>> +  ret i32 %Q
>> +}
>>
>>
> You might want to write a similar testcase replacing the "xor" with an
> "or".
>
> -Eli
>
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