proposal: time: compress implementation for `time.Now()`

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Go Programming Experience

Advanced

Other Languages Experience

C/C++, JavaScript

Related Idea

• Has this idea, or one like it, been proposed before?
• Does this affect error handling?
• Is this about generics?
• Is this change backward compatible? Breaking the Go 1 compatibility guarantee is a large cost and requires a large benefit

Has this idea, or one like it, been proposed before?

No

Does this affect error handling?

No

Is this about generics?

No

Proposal

Why to differ monotonic time? Simplification will help to reduce running time and make time.Now() more exact.

Compare

func Now() Time {
	sec, nsec, _ := runtimeNow()
	return Time{uint64(nsec), sec + unixToInternal, Local}
}

and

func Now() Time {
	sec, nsec, mono := runtimeNow()
	if mono == 0 {
		return Time{uint64(nsec), sec + unixToInternal, Local}
	}
	mono -= startNano
	sec += unixToInternal - minWall
	if uint64(sec)>>33 != 0 {
		// Seconds field overflowed the 33 bits available when
		// storing a monotonic time. This will be true after
		// March 16, 2157.
		return Time{uint64(nsec), sec + minWall, Local}
	}
	return Time{hasMonotonic | uint64(sec)<<nsecShift | uint64(nsec), mono, Local}
}

Language Spec Changes

None

Informal Change

No response

Is this change backward compatible?

Yes. Nothing else changes to the exported methods of time.Time.

Orthogonality: How does this change interact or overlap with existing features?

No response

Would this change make Go easier or harder to learn, and why?

No response

Cost Description

No response

Changes to Go ToolChain

No response

Performance Costs

No response

Prototype

No response