Target structv0.1.0

Properties of the machine the build targets.

pub struct Target {
    pub os: OperatingSystem;
    pub arch: Architecture;
    pub abi: ApplicationBinaryInterface;
    pub endian: Endianness;
    pub pointerBits: uint;
    pub dataModel: DataModel;
    pub objectFormat: ObjectFormat;
    pub triple: char8[..];
}

Every field is fixed when compiling begins. Reading one produces no runtime code, so a branch on a field is decided while compiling and the untaken side is not emitted.

Fields

Name	Type	Description
`os`	`OperatingSystem`	The operating system.
`arch`	`Architecture`	The processor architecture.
`abi`	`ApplicationBinaryInterface`	The calling and layout conventions the target's code follows.
`endian`	`Endianness`	The order the target stores a multi-byte value's bytes in.
`pointerBits`	`uint`	How many bits a pointer occupies.
`dataModel`	`DataModel`	The widths the target's C environment assigns to `long` and to a pointer.
`objectFormat`	`ObjectFormat`	The object-file format compiled code is emitted in.
`triple`	`char8[..]`	The canonical target name, spelled `<os>-<arch>`, which is what `--target` accepts.

Methods

`HasFeature`

pub func HasFeature(
    self: &Target,
    feature: TargetFeature
) -> bool

Whether the build enables feature on this target. self is borrowed and feature is read by value. Answered while compiling, so a branch on it emits only the side that applies and a body using an instruction the feature provides is never emitted without it. Cannot fail: a feature the target does not have is absent rather than an error. Costs nothing in the built program.

Name	Type	Description
`feature`	`TargetFeature`	the target feature to ask about

Returns: whether the target being built for has it

Source

`OperatingSystem`

pub enum OperatingSystem: uint8 {
    Unknown = 0,
    FreeBSD = 1,
    Linux = 2,
    macOS = 3,
    Windows = 4
}

An operating system a build can target. Named per system rather than per family, so a package can tell FreeBSD from Linux where their interfaces differ.

Source

Cases

Name	Value	Description
`Unknown`	`0`	A target the compiler has no name for, which no supported build produces.
`FreeBSD`	`1`	FreeBSD. Told apart from the other BSDs, which this enumeration also names.
`Linux`	`2`	Linux, any distribution.
`macOS`	`3`	Apple macOS.
`Windows`	`4`	Microsoft Windows.

`Architecture`

pub enum Architecture: uint8 {
    Unknown = 0,
    AArch64 = 1,
    X86_64 = 2
}

A processor architecture a build can target.

Source

Cases

Name	Value	Description
`Unknown`	`0`	An architecture the compiler has no name for, which no supported build produces.
`AArch64`	`1`	The 64-bit Arm architecture.
`X86_64`	`2`	The 64-bit x86 architecture.

`ApplicationBinaryInterface`

pub enum ApplicationBinaryInterface: uint8 {
    Unknown = 0,
    AAPCS64 = 1,
    SystemV = 2,
    WindowsX64 = 3
}

The calling and layout conventions a target's code follows. This is what decides how arguments are passed and how aggregates are laid out, so a declaration that has to match a foreign interface branches on it rather than on the operating system.

Source

Cases

Name	Value	Description
`Unknown`	`0`	An ABI the compiler has no name for, which no supported build produces.
`AAPCS64`	`1`	The AArch64 procedure call standard.
`SystemV`	`2`	The System V AMD64 ABI, used by Linux, FreeBSD, and macOS on x86-64.
`WindowsX64`	`3`	The Windows x64 calling convention.

`TargetFeature`

pub enum TargetFeature: uint8 {
    AVX = 0,
    AVX2 = 1,
    AVX512 = 2,
    NEON = 3,
    SSE2 = 4,
    SSE3 = 5,
    SSE41 = 6,
    SSE42 = 7,
    SSSE3 = 8,
    SVE = 9
}

A processor feature a target may be built with. Presence is asked about with Target::HasFeature rather than read as a field, because a build enables a set rather than a single one.

Source

Cases

Name	Value	Description
`AVX`	`0`	x86 Advanced Vector Extensions.
`AVX2`	`1`	x86 Advanced Vector Extensions 2.
`AVX512`	`2`	x86 Advanced Vector Extensions 512.
`NEON`	`3`	Arm Advanced SIMD.
`SSE2`	`4`	x86 Streaming SIMD Extensions 2.
`SSE3`	`5`	x86 Streaming SIMD Extensions 3.
`SSE41`	`6`	x86 Streaming SIMD Extensions 4.1.
`SSE42`	`7`	x86 Streaming SIMD Extensions 4.2.
`SSSE3`	`8`	x86 Supplemental Streaming SIMD Extensions 3.
`SVE`	`9`	Arm Scalable Vector Extension.

`Endianness`

pub enum Endianness: uint8 {
    Big = 0,
    Little = 1
}

The order a target stores a multi-byte value's bytes in.

Source

Cases

Name	Value	Description
`Big`	`0`	Most significant byte first, which is network byte order.
`Little`	`1`	Least significant byte first, which every currently supported target uses.

`DataModel`

pub enum DataModel: uint8 {
    Unknown = 0,
    LLP64 = 1,
    LP64 = 2
}

The widths a target's C environment assigns to long and to a pointer. This is what a raw C declaration needs to get long right, since the two models disagree about it.

Source

Cases

Name	Value	Description
`Unknown`	`0`	A model the compiler has no name for, which no supported build produces.
`LLP64`	`1`	32-bit `long`, 64-bit pointer. Windows.
`LP64`	`2`	64-bit `long`, 64-bit pointer. Every supported Unix target.

`ObjectFormat`

pub enum ObjectFormat: uint8 {
    Unknown = 0,
    COFF = 1,
    ELF = 2,
    MachO = 3
}

The object-file format a target's compiled code is emitted in.

Source

Cases

Name	Value	Description
`Unknown`	`0`	A format the compiler has no name for, which no supported build produces.
`COFF`	`1`	The format Windows links, carried in a PE image.
`ELF`	`2`	The format Linux and FreeBSD link.
`MachO`	`3`	The format macOS links.

`#target`

pub const #target: Target;

The machine being compiled for, as a compile-time value. Reading a field produces no runtime code. A when on one keeps only the branch that applies, so the untaken side is never resolved or type-checked and may name declarations this target does not have.

Source

The location of the expression that reads it.

Integer arithmetic

Checked, wrapping and saturating arithmetic at every integer width, the limits of an integer type, and the uint64 intrinsics allocation sizes are computed with.

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