sys

Documentation

Overview

package sys contains system- and configuration- and architecture-specific constants used by the runtime.

Index

• Constants
• func Bswap32(x uint32) uint32
• func Bswap64(x uint64) uint64
• func Ctz32(x uint32) int
• func Ctz64(x uint64) int
• func Ctz8(x uint8) int
• func LeadingZeros64(x uint64) int
• func LeadingZeros8(x uint8) int
• func Len64(x uint64) (n int)
• func Len8(x uint8) int
• func OnesCount64(x uint64) int
• func Prefetch(addr uintptr)
• func PrefetchStreamed(addr uintptr)
• func TrailingZeros64(x uint64) int
• func TrailingZeros8(x uint8) int

Constants

const DefaultPhysPageSize = goarch.DefaultPhysPageSize

DefaultPhysPageSize is the default physical page size.

const Int64Align = goarch.PtrSize

Int64Align is the required alignment for a 64-bit integer (4 on 32-bit systems, 8 on 64-bit).

const MinFrameSize = goarch.MinFrameSize

MinFrameSize is the size of the system-reserved words at the bottom of a frame (just above the architectural stack pointer). It is zero on x86 and PtrSize on most non-x86 (LR-based) systems. On PowerPC it is larger, to cover three more reserved words: the compiler word, the link editor word, and the TOC save word.

const PCQuantum = goarch.PCQuantum

PCQuantum is the minimal unit for a program counter (1 on x86, 4 on most other systems). The various PC tables record PC deltas pre-divided by PCQuantum.

const StackAlign = goarch.StackAlign

StackAlign is the required alignment of the SP register. The stack must be at least word aligned, but some architectures require more.

const StackGuardMultiplier = StackGuardMultiplierDefault*(1-goos.IsAix) + 2*goos.IsAix

AIX requires a larger stack for syscalls.

Functions

func Bswap32

func Bswap32(x uint32) uint32

Bswap32 returns its input with byte order reversed 0x01020304 -> 0x04030201

func Bswap64

func Bswap64(x uint64) uint64

Bswap64 returns its input with byte order reversed 0x0102030405060708 -> 0x0807060504030201

func Ctz32

func Ctz32(x uint32) int

Ctz32 counts trailing (low-order) zeroes, and if all are zero, then 32.

func Ctz64

func Ctz64(x uint64) int

Ctz64 counts trailing (low-order) zeroes, and if all are zero, then 64.

func Ctz8

func Ctz8(x uint8) int

Ctz8 returns the number of trailing zero bits in x; the result is 8 for x == 0.

func LeadingZeros64

func LeadingZeros64(x uint64) int

LeadingZeros64 returns the number of leading zero bits in x; the result is 64 for x == 0.

func LeadingZeros8

func LeadingZeros8(x uint8) int

LeadingZeros8 returns the number of leading zero bits in x; the result is 8 for x == 0.

func Len64

func Len64(x uint64) (n int)

len64 returns the minimum number of bits required to represent x; the result is 0 for x == 0.

func Len8

func Len8(x uint8) int

Len8 returns the minimum number of bits required to represent x; the result is 0 for x == 0.

func OnesCount64

func OnesCount64(x uint64) int

OnesCount64 returns the number of one bits ("population count") in x.

func Prefetch

func Prefetch(addr uintptr)

Prefetch prefetches data from memory addr to cache

AMD64: Produce PREFETCHT0 instruction

ARM64: Produce PRFM instruction with PLDL1KEEP option

func PrefetchStreamed

func PrefetchStreamed(addr uintptr)

PrefetchStreamed prefetches data from memory addr, with a hint that this data is being streamed. That is, it is likely to be accessed very soon, but only once. If possible, this will avoid polluting the cache.

AMD64: Produce PREFETCHNTA instruction

ARM64: Produce PRFM instruction with PLDL1STRM option

func TrailingZeros64

func TrailingZeros64(x uint64) int

TrailingZeros64 returns the number of trailing zero bits in x; the result is 64 for x == 0.

func TrailingZeros8

func TrailingZeros8(x uint8) int

TrailingZeros8 returns the number of trailing zero bits in x; the result is 8 for x == 0.