CODEWITHSUNDEEP
phpperformanceincrement
Purushottam
Purushottam

Reputation: 844

Why is x = x+1 slower than x += 1?

I am a PHP programmer. I always prefer to use x += 1; instead of x = x + 1;.

But still I don't understand why people say execution of x += 1; is faster than x = x + 1;.

(editor's note: This question didn't originally specify PHP, hence the comments and answers talking about C++ compilers.)

Upvotes: 1

Views: 1196

Answers (3)

mcq8
mcq8

Reputation: 247

http://3v4l.org/GjPvL/vld#tabs will show you the answer.

$x += 1; is interpreted as ASSIGN_ADD

$x = $x + 1; has a separate add and assign operation and uses a temporary variable.

The less opcode, the faster it will run(in most cases).

Note that if you enable opcache with code optimization, $x = $x + 1; will be optimized to use ASSIGN_ADD.

Upvotes: 4

Luke Xu
Luke Xu

Reputation: 2440

Decent compilers will pick up that

x = x +1
x += 1
x++

to be the same and in the end compile the same code, thus providing no difference.

Upvotes: 1

CleverLikeAnOx
CleverLikeAnOx

Reputation: 1496

+= is what is called syntactic sugar. This is a convenience for developers. The two statements should have identical results in terms of logic and performance.

Upvotes: 1

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