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Fix the meaning of ISA to be Instruction Set Architecture #44180

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Jan 8, 2025
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Fix the meaning of ISA to be Instruction Set Architecture #44180

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Fix the meaning of ISA to be Instruction Set Architecture
tannergooding Jan 8, 2025
ab70468
Update docs/core/compatibility/core-libraries/5.0/sse-comparegreatert…
tannergooding Jan 8, 2025
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2 changes: 1 addition & 1 deletion ...ore/compatibility/core-libraries/5.0/hardware-instrinsics-issupported-checks.md
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Expand Up @@ -8,7 +8,7 @@ ms.date: 11/01/2020
Checking `<Isa>.X64.IsSupported`, where `<Isa>` refers to the classes in the <xref:System.Runtime.Intrinsics.X86?displayProperty=nameWithType> namespace, may now produce a different result to previous versions of .NET.

> [!TIP]
> *ISA* stands for industry standard architecture.
> *ISA* stands for Instruction Set Architecture.

## Version introduced

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2 changes: 1 addition & 1 deletion docs/core/compatibility/core-libraries/5.0/sse-comparegreaterthan-intrinsics.md
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Expand Up @@ -22,7 +22,7 @@ Previously, `NaN` inputs to the listed <xref:System.Runtime.Intrinsics.X86.Sse>

Starting in .NET 5, these methods correctly handle `NaN` inputs and return the same results as the corresponding methods in the <xref:System.Runtime.Intrinsics.X86.Avx> class.

The Streaming SIMD Extensions (SSE) and Streaming SIMD Extensions 2 (SSE2) industry standard architectures (ISAs) don't provide direct hardware support for these comparison methods, so they're implemented in software. Previously, the methods were improperly implemented, and they incorrectly handled `NaN` inputs. For code ported from native, the incorrect behavior may introduce bugs. For a 256-bit code path, the methods can also produce different results to the equivalent methods in the <xref:System.Runtime.Intrinsics.X86.Avx> class.
The Streaming SIMD Extensions (SSE) and Streaming SIMD Extensions 2 (SSE2) Industry Set Architectures (ISAs) don't provide direct hardware support for these comparison methods, so they're implemented in software. Previously, the methods were improperly implemented, and they incorrectly handled `NaN` inputs. For code ported from native, the incorrect behavior may introduce bugs. For a 256-bit code path, the methods can also produce different results to the equivalent methods in the <xref:System.Runtime.Intrinsics.X86.Avx> class.

As an example of how the methods were previously incorrect, you can implement `CompareNotGreaterThan(x,y)` as `CompareLessThanOrEqual(x,y)` for regular integers. However, for `NaN` inputs, that logic computes the wrong result. Instead, using `CompareNotLessThan(y,x)` compares the numbers correctly *and* takes `NaN` inputs into consideration.

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