[llvm] r303387 - [InstCombine] add more tests for xor-of-icmps; NFC

[Davide Italiano via llvm-commits]

On Thu, May 18, 2017 at 4:10 PM, Davide Italiano <davide at freebsd.org> wrote:
> On Thu, May 18, 2017 at 3:47 PM, Sanjay Patel via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
>> Author: spatel
>> Date: Thu May 18 17:47:57 2017
>> New Revision: 303387
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=303387&view=rev
>> Log:
>> [InstCombine] add more tests for xor-of-icmps; NFC
>>
>> Modified:
>>     llvm/trunk/test/Transforms/InstCombine/set.ll
>>
>> Modified: llvm/trunk/test/Transforms/InstCombine/set.ll
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/set.ll?rev=303387&r1=303386&r2=303387&view=diff
>> ==============================================================================
>> --- llvm/trunk/test/Transforms/InstCombine/set.ll (original)
>> +++ llvm/trunk/test/Transforms/InstCombine/set.ll Thu May 18 17:47:57 2017
>> @@ -175,6 +175,36 @@ define i1 @xor_of_icmps(i64 %a) {
>>    ret i1 %xor
>>  }
>>
>> +; FIXME: This is also equivalent to the previous test.
>> +
>> +define i1 @xor_of_icmps_commute(i64 %a) {
>> +; CHECK-LABEL: @xor_of_icmps_commute(
>> +; CHECK-NEXT:    [[B:%.*]] = icmp sgt i64 %a, 0
>> +; CHECK-NEXT:    [[C:%.*]] = icmp eq i64 %a, 1
>> +; CHECK-NEXT:    [[XOR:%.*]] = xor i1 [[B]], [[C]]
>> +; CHECK-NEXT:    ret i1 [[XOR]]
>> +;
>> +  %b = icmp sgt i64 %a, 0
>> +  %c = icmp eq i64 %a, 1
>> +  %xor = xor i1 %b, %c
>> +  ret i1 %xor
>> +}
>> +
>> +; FIXME: This is (a != 5).
>> +
>> +define i1 @xor_of_icmps_folds_more(i64 %a) {
>> +; CHECK-LABEL: @xor_of_icmps_folds_more(
>> +; CHECK-NEXT:    [[B:%.*]] = icmp sgt i64 %a, 4
>> +; CHECK-NEXT:    [[C:%.*]] = icmp slt i64 %a, 6
>> +; CHECK-NEXT:    [[XOR:%.*]] = xor i1 [[B]], [[C]]
>> +; CHECK-NEXT:    ret i1 [[XOR]]
>> +;
>
> You can start from having these in `-instcombine`, but these (and
> other tests) seems like a VRP problem to me. I haven't studied this
> carefully, but I wonder why we don't catch these. Have you tried to
> evaluate why our VRP pass doesn't handle these?
>
> --
> Davide

Not necessarily complaining about having these as combiners, but I'd
first like to understand why we don't catch these somewhere else :)

-- 
Davide

"There are no solved problems; there are only problems that are more
or less solved" -- Henri Poincare