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UInt128 improve division by 64 bit on x64 #99747

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merged 8 commits into from
Oct 30, 2024
+15 −0
Merged

UInt128 improve division by 64 bit on x64 #99747

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c88a477
Add fast path for UInt128 division on x64 when divisor is as most 64bits
Daniel-Svensson Mar 11, 2024
a5dd98e
Update src/libraries/System.Private.CoreLib/src/System/UInt128.cs
Daniel-Svensson Mar 14, 2024
60cc066
Supress warning CA2252 // This API requires opting into preview features
Daniel-Svensson Jun 7, 2024
19b92d9
Check upper bits for 0 and do normal divion for x64 (faster when it i…
Daniel-Svensson Jun 11, 2024
6980103
Merge branch 'main' into fast_x64_uint128_div
tannergooding Jul 10, 2024
740c48d
Merge remote-tracking branch 'upstream/main' into fast_x64_uint128_div
Daniel-Svensson Sep 12, 2024
6d185b3
Change supression to SYSLIB5004 after DivRem was changes to [Experime…
Daniel-Svensson Sep 12, 2024
0c81985
Merge remote-tracking branch 'origin/fast_x64_uint128_div' into fast_…
Daniel-Svensson Sep 12, 2024
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15 changes: 15 additions & 0 deletions src/libraries/System.Private.CoreLib/src/System/UInt128.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Intrinsics.X86;

namespace System
{
Expand Down Expand Up @@ -1103,6 +1104,20 @@ public static UInt128 Log2(UInt128 value)
// left and right are both uint64
return left._lower / right._lower;
}
else if (X86Base.X64.IsSupported)
{
ulong highRes = 0ul;
ulong remainder = left._upper;

#pragma warning disable SYSLIB5004 // DivRem is marked as [Experimental], partly because it does not get optmized by the JIT for constant inputs
if (remainder >= right._lower)
{
(highRes, remainder) = X86Base.X64.DivRem(left._upper, 0, right._lower);
}

return new UInt128(highRes, X86Base.X64.DivRem(left._lower, remainder, right._lower).Quotient);
#pragma warning restore SYSLIB5004 // DivRem is marked as [Experimental]
}
}

if (right >= left)
Expand Down
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