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Add flags checks to BMI1 intrinsic lowering (#66736)
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* add flags checks to BMI1 intrinsic lowering to prevent decomposed longs in x84 from being altered

* update bmji1intrinsics tests
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@Wraith2
Wraith2 authored Mar 20, 2022
1 parent 35be545 commit fa1f283
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Showing 2 changed files with 75 additions and 9 deletions.
19 changes: 19 additions & 0 deletions src/coreclr/jit/lowerxarch.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3789,6 +3789,13 @@ GenTree* Lowering::TryLowerAndOpToResetLowestSetBit(GenTreeOp* andNode)
return nullptr;
}

// Subsequent nodes may rely on CPU flags set by these nodes in which case we cannot remove them
if (((addOp2->gtFlags & GTF_SET_FLAGS) != 0) || ((op2->gtFlags & GTF_SET_FLAGS) != 0) ||
((andNode->gtFlags & GTF_SET_FLAGS) != 0))
{
return nullptr;
}

NamedIntrinsic intrinsic;
if (op1->TypeIs(TYP_LONG) && comp->compOpportunisticallyDependsOn(InstructionSet_BMI1_X64))
{
Expand Down Expand Up @@ -3868,6 +3875,12 @@ GenTree* Lowering::TryLowerAndOpToExtractLowestSetBit(GenTreeOp* andNode)
return nullptr;
}

// Subsequent nodes may rely on CPU flags set by these nodes in which case we cannot remove them
if (((opNode->gtFlags & GTF_SET_FLAGS) != 0) || ((negNode->gtFlags & GTF_SET_FLAGS) != 0))
{
return nullptr;
}

NamedIntrinsic intrinsic;
if (andNode->TypeIs(TYP_LONG) && comp->compOpportunisticallyDependsOn(InstructionSet_BMI1_X64))
{
Expand Down Expand Up @@ -3947,6 +3960,12 @@ GenTree* Lowering::TryLowerAndOpToAndNot(GenTreeOp* andNode)
return nullptr;
}

// Subsequent nodes may rely on CPU flags set by these nodes in which case we cannot remove them
if (((andNode->gtFlags & GTF_SET_FLAGS) != 0) || ((notNode->gtFlags & GTF_SET_FLAGS) != 0))
{
return nullptr;
}

NamedIntrinsic intrinsic;
if (andNode->TypeIs(TYP_LONG) && comp->compOpportunisticallyDependsOn(InstructionSet_BMI1_X64))
{
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65 changes: 56 additions & 9 deletions src/tests/JIT/Intrinsics/BMI1Intrinsics.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -25,29 +25,76 @@ static int Main(string[] args)

foreach (var value in values)
{
Test(value.input1, AndNot(value.input1, value.input2), value.andnExpected, nameof(AndNot));
Test(value.input1, ExtractLowestSetIsolatedBit(value.input1), value.blsiExpected, nameof(ExtractLowestSetIsolatedBit));
Test(value.input1, ResetLowestSetBit(value.input1), value.blsrExpected, nameof(ResetLowestSetBit));
Test(value.input1, GetMaskUpToLowestSetBit(value.input1), value.blmskExpected, nameof(GetMaskUpToLowestSetBit));
Test(value.input1, AndNot_32bit(value.input1, value.input2), value.andnExpected, nameof(AndNot_32bit));
Test(value.input1, ExtractLowestSetIsolatedBit_32bit(value.input1), value.blsiExpected, nameof(ExtractLowestSetIsolatedBit_32bit));
Test(value.input1, ResetLowestSetBit_32bit(value.input1), value.blsrExpected, nameof(ResetLowestSetBit_32bit));
Test(value.input1, GetMaskUpToLowestSetBit_32bit(value.input1), value.blmskExpected, nameof(GetMaskUpToLowestSetBit_32bit));
}


var values2 = new (ulong input1, ulong input2, ulong andnExpected, ulong blsiExpected, ulong blsrExpected, ulong blmskExpected)[] {
(0, 0, 0, 0, 0, 0),
(1, 0, 1, 1, 0,0xFFFFFFFF_FFFFFFFE),
(ulong.MaxValue / 2, 0,0x7FFFFFFF_FFFFFFFF, 1,0x7FFFFFFF_FFFFFFFE,0xFFFFFFFF_FFFFFFFE),
((ulong.MaxValue / 2) - 1, 0,0x7FFFFFFF_FFFFFFFE, 2,0x7FFFFFFF_FFFFFFFC,0xFFFFFFFF_FFFFFFFC),
((ulong.MaxValue / 2) + 1, 0,0x80000000_00000000,0x80000000_00000000, 0, 0),
(ulong.MaxValue - 1, 0,0xFFFFFFFF_FFFFFFFE, 2,0xFFFFFFFF_FFFFFFFC,0xFFFFFFFF_FFFFFFFC),
(ulong.MaxValue, 0,0xFFFFFFFF_FFFFFFFF, 1,0xFFFFFFFF_FFFFFFFE,0xFFFFFFFF_FFFFFFFE),
(0xAAAAAAAA_AAAAAAAA,0xAAAAAAAA_AAAAAAAA, 0, 2,0xAAAAAAAA_AAAAAAA8,0xFFFFFFFF_FFFFFFFC),
(0xAAAAAAAA_AAAAAAAA,0x55555555_55555555,0xAAAAAAAA_AAAAAAAA, 2,0xAAAAAAAA_AAAAAAA8,0xFFFFFFFF_FFFFFFFC),
};

foreach (var value in values2)
{
Test(value.input1, AndNot_64bit(value.input1, value.input2), value.andnExpected, nameof(AndNot_64bit));
Test(value.input1, ExtractLowestSetIsolatedBit_64bit(value.input1), value.blsiExpected, nameof(ExtractLowestSetIsolatedBit_64bit));
Test(value.input1, ResetLowestSetBit_64bit(value.input1), value.blsrExpected, nameof(ResetLowestSetBit_64bit));
Test(value.input1, GetMaskUpToLowestSetBit_64bit(value.input1), value.blmskExpected, nameof(GetMaskUpToLowestSetBit_64bit));
}

return _errorCode;
}

[MethodImpl(MethodImplOptions.NoInlining)]
private static uint AndNot(uint x, uint y) => x & (~y); // bmi1 andn
private static uint AndNot_32bit(uint x, uint y) => x & (~y); // bmi1 andn

[MethodImpl(MethodImplOptions.NoInlining)]
private static ulong AndNot_64bit(ulong x, ulong y) => x & (~y); // bmi1 andn

[MethodImpl(MethodImplOptions.NoInlining)]
private static uint ExtractLowestSetIsolatedBit_32bit(uint x) => (uint)(x & (-x)); // bmi1 blsi

[MethodImpl(MethodImplOptions.NoInlining)]
private static ulong ExtractLowestSetIsolatedBit_64bit(ulong x) => x & (ulong)(-(long)x); // bmi1 blsi

[MethodImpl(MethodImplOptions.NoInlining)]
private static uint ResetLowestSetBit_32bit(uint x) => x & (x - 1); // bmi1 blsr

[MethodImpl(MethodImplOptions.NoInlining)]
private static uint ExtractLowestSetIsolatedBit(uint x) => (uint)(x & (-x)); // bmi1 blsi
private static ulong ResetLowestSetBit_64bit(ulong x) => x & (x - 1); // bmi1 blsr

[MethodImpl(MethodImplOptions.NoInlining)]
private static uint ResetLowestSetBit(uint x) => x & (x - 1); // bmi1 blsr
private static uint GetMaskUpToLowestSetBit_32bit(uint x) => (uint)(x ^ (-x)); // bmi1 blmsk

[MethodImpl(MethodImplOptions.NoInlining)]
private static uint GetMaskUpToLowestSetBit(uint x) => (uint)(x ^ (-x)); // bmi1 blmsk
private static ulong GetMaskUpToLowestSetBit_64bit(ulong x) => x ^ (ulong)(-(long)x); // bmi1 blmsk

[MethodImpl(MethodImplOptions.NoInlining)]
private static void Test(uint input, uint output, uint expected, string callerName)
{
if (output != expected)
{
Console.WriteLine($"{callerName} failed.");
Console.WriteLine($"Input: {input:X}");
Console.WriteLine($"Output: {output:X}");
Console.WriteLine($"Expected: {expected:X}");

_errorCode++;
}
}

[MethodImpl(MethodImplOptions.NoInlining)]
private static void Test(uint input, uint output, uint expected,string callerName)
private static void Test(ulong input, ulong output, ulong expected, string callerName)
{
if (output != expected)
{
Expand Down

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