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/arch (x64)

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Specifies the architecture for code generation on x64. For more information on /arch for other target architectures, see /arch (x86), /arch (ARM64), and /arch (ARM).

Syntax

/arch:[SSE2|SSE4.2|AVX|AVX2|AVX512|AVX10.1]

Arguments

/arch:SSE2
Enables Intel Streaming SIMD Extensions 2. The default instruction set is SSE2 if no /arch option is specified.

/arch:SSE4.2
Enables Intel Streaming SIMD Extensions 4.2.

/arch:AVX
Enables Intel Advanced Vector Extensions.

/arch:AVX2
Enables Intel Advanced Vector Extensions 2.

/arch:AVX512
Enables Intel Advanced Vector Extensions 512.

/arch:AVX10.1
Enables Intel Advanced Vector Extensions 10 version 1.

Remarks

The /arch option enables the use of certain instruction set extensions, particularly for vector calculation, available in processors from Intel and AMD. In general, more recently introduced processors may support extensions beyond the ones supported by older processors, although you should consult the documentation for a particular processor or test for instruction set extension support using __cpuid before executing code using an instruction set extension. You can also use the __check_isa_support intrinsic to check for more frequently used CPU features.

/arch only affects code generation for native functions. When you use /clr to compile, /arch has no effect on code generation for managed functions.

The processor extensions have the following characteristics:

  • The default mode uses SSE2 instructions for scalar floating-point and vector calculations. These instructions allow calculation with 128-bit vectors of single-precision, double-precision and 1, 2, 4 or 8-byte integer values, as well as single-precision and double-precision scalar floating-point values.

  • SSE4.2 uses the full set of SSE instructions for floating-point scalar, vector, and integer vector calculations.

  • AVX introduced an alternative instruction encoding for vector and floating-point scalar instructions. It allows vectors of either 128 bits or 256 bits, and zero-extends all vector results to the full vector size. (For legacy compatibility, SSE-style vector instructions preserve all bits beyond bit 127.) Most floating-point operations are extended to 256 bits.

  • AVX2 extends most integer operations to 256-bit vectors and enables use of Fused Multiply-Add (FMA) instructions.

  • AVX-512 introduced another instruction encoding form that allows 512-bit vectors, masking, embedded rounding/broadcast, and new instructions. The default vector length for AVX-512 is 512 bits and can be changed to 256 bits using the /vlen flag.

  • AVX10.1 adds more instructions on top of AVX-512. The default vector length for AVX10.1 is 256 bits and can be changed to 512 bits using the /vlen flag.

Each /arch option may also enable the use of other non-vector instructions that are associated with that option. An example is the use of certain BMI instructions when /arch:AVX2 is specified.

The __AVX__ preprocessor symbol is defined when the /arch:AVX, /arch:AVX2, /arch:AVX512, or /arch:AVX10.1 compiler option is specified. The __AVX2__ preprocessor symbol is defined when the /arch:AVX2, /arch:AVX512, or /arch:AVX10.1 compiler option is specified. The __AVX512F__, __AVX512CD__, __AVX512BW__, __AVX512DQ__, and __AVX512VL__ preprocessor symbols are defined when the /arch:AVX512, or /arch:AVX10.1 compiler option is specified. The __AVX10_VER__ preprocessor symbol is defined when the /arch:AVX10.1 compiler option is specified. It indicates the AVX10 version the compiler is targeting. For more information, see Predefined macros. The /arch:AVX2 option was introduced in Visual Studio 2013 Update 2, version 12.0.34567.1. Limited support for /arch:AVX512 was added in Visual Studio 2017, and expanded in Visual Studio 2019. Support for /arch:AVX10.1 was added in Visual Studio 2022.

To set the /arch compiler option in Visual Studio

  1. Open the Property Pages dialog box for the project. For more information, see Set C++ compiler and build properties in Visual Studio.

  2. Select the Configuration Properties > C/C++ > Code Generation property page.

  3. Modify the Enable Enhanced Instruction Set property.

To set this compiler option programmatically

See also

/arch (Minimum CPU Architecture)
MSVC compiler options
MSVC compiler command-line syntax