[llvm] b38d897 - [ConstantRange] binaryXor(): special-case binary complement case - the result is precise

[Roman Lebedev via llvm-commits]

On Tue, Sep 22, 2020 at 9:47 PM Nikita Popov <nikita.ppv at gmail.com> wrote:
>
> On Tue, Sep 22, 2020 at 8:38 PM Roman Lebedev via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>>
>>
>> Author: Roman Lebedev
>> Date: 2020-09-22T21:37:29+03:00
>> New Revision: b38d897e802664034c7e6e4654328256ed370a61
>>
>> URL: https://github.com/llvm/llvm-project/commit/b38d897e802664034c7e6e4654328256ed370a61
>> DIFF: https://github.com/llvm/llvm-project/commit/b38d897e802664034c7e6e4654328256ed370a61.diff
>>
>> LOG: [ConstantRange] binaryXor(): special-case binary complement case - the result is precise
>>
>> Use the fact that `~X` is equivalent to `-1 - X`, which gives us
>> fully-precise answer, and we only need to special-handle the wrapped case.
>>
>> This fires ~16k times for vanilla llvm test-suite + RawSpeed.
>>
>> Added:
>>
>>
>> Modified:
>>     llvm/include/llvm/IR/ConstantRange.h
>>     llvm/lib/IR/ConstantRange.cpp
>>     llvm/unittests/IR/ConstantRangeTest.cpp
>>
>> Removed:
>>
>>
>>
>> ################################################################################
>> diff  --git a/llvm/include/llvm/IR/ConstantRange.h b/llvm/include/llvm/IR/ConstantRange.h
>> index 318532b24e83..494a14a10cdb 100644
>> --- a/llvm/include/llvm/IR/ConstantRange.h
>> +++ b/llvm/include/llvm/IR/ConstantRange.h
>> @@ -409,6 +409,11 @@ class LLVM_NODISCARD ConstantRange {
>>    /// value in \p Other.
>>    ConstantRange srem(const ConstantRange &Other) const;
>>
>> +  /// Return a new range representing the possible values resulting from
>> +  /// a binary-xor of a value in this range by an all-one value,
>> +  /// aka bitwise complement operation.
>> +  ConstantRange binaryNot() const;
>> +
>>    /// Return a new range representing the possible values resulting
>>    /// from a binary-and of a value in this range by a value in \p Other.
>>    ConstantRange binaryAnd(const ConstantRange &Other) const;
>>
>> diff  --git a/llvm/lib/IR/ConstantRange.cpp b/llvm/lib/IR/ConstantRange.cpp
>> index 396c39b5b3a8..7b8dd66b993c 100644
>> --- a/llvm/lib/IR/ConstantRange.cpp
>> +++ b/llvm/lib/IR/ConstantRange.cpp
>> @@ -1240,6 +1240,16 @@ ConstantRange ConstantRange::srem(const ConstantRange &RHS) const {
>>    return ConstantRange(std::move(Lower), std::move(Upper));
>>  }
>>
>> +ConstantRange ConstantRange::binaryNot() const {
>> +  if (isEmptySet())
>> +    return getEmpty();
>> +
>> +  if (isWrappedSet())
>> +    return getFull();
>
>
> Probably don't need those checks, as you're forwarding to the sub() implementation anyway?
It is needed if we want to give the right answer.

> Nikita
Roman

>>
>> +
>> +  return ConstantRange(APInt::getAllOnesValue(getBitWidth())).sub(*this);
>> +}
>> +
>>  ConstantRange
>>  ConstantRange::binaryAnd(const ConstantRange &Other) const {
>>    if (isEmptySet() || Other.isEmptySet())
>> @@ -1278,6 +1288,12 @@ ConstantRange ConstantRange::binaryXor(const ConstantRange &Other) const {
>>    if (isSingleElement() && Other.isSingleElement())
>>      return {*getSingleElement() ^ *Other.getSingleElement()};
>>
>> +  // Special-case binary complement, since we can give a precise answer.
>> +  if (Other.isSingleElement() && Other.getSingleElement()->isAllOnesValue())
>> +    return binaryNot();
>> +  if (isSingleElement() && getSingleElement()->isAllOnesValue())
>> +    return Other.binaryNot();
>> +
>>    // TODO: replace this with something less conservative
>>    return getFull();
>>  }
>>
>> diff  --git a/llvm/unittests/IR/ConstantRangeTest.cpp b/llvm/unittests/IR/ConstantRangeTest.cpp
>> index 8bcc6efdc265..474a94af3932 100644
>> --- a/llvm/unittests/IR/ConstantRangeTest.cpp
>> +++ b/llvm/unittests/IR/ConstantRangeTest.cpp
>> @@ -2349,4 +2349,22 @@ TEST_F(ConstantRangeTest, binaryXor) {
>>    EXPECT_TRUE(R0_99.binaryXor(R16_35).isFullSet());
>>  }
>>
>> +TEST_F(ConstantRangeTest, binaryNot) {
>> +  TestUnsignedUnaryOpExhaustive(
>> +      [](const ConstantRange &CR) { return CR.binaryNot(); },
>> +      [](const APInt &N) { return ~N; });
>> +  TestUnsignedUnaryOpExhaustive(
>> +      [](const ConstantRange &CR) {
>> +        return CR.binaryXor(
>> +            ConstantRange(APInt::getAllOnesValue(CR.getBitWidth())));
>> +      },
>> +      [](const APInt &N) { return ~N; });
>> +  TestUnsignedUnaryOpExhaustive(
>> +      [](const ConstantRange &CR) {
>> +        return ConstantRange(APInt::getAllOnesValue(CR.getBitWidth()))
>> +            .binaryXor(CR);
>> +      },
>> +      [](const APInt &N) { return ~N; });
>> +}
>> +
>>  }  // anonymous namespace
>>
>>
>>
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