DIP56

Title:	Provide pragma to control function inlining
DIP:	56
Version:	0
Status:	Draft
Created:	2014-02-23
Last Modified:	2015-02-03
Author:	Walter Bright
Links:

Abstract

This proposal uses pragmas to add inlining instructions to the compiler.

Rationale

Sometimes generating better code requires runtime profile information. But being a static compiler, not a JIT, the compiler could use such hints from the programmer.

Description

This adds a pragma 'inline' and two values for it: true and false, which influences the inlining of the function they appear in. 'true' means always inline, 'false' means never inline, no argument means default behavior.

If this pragma is outside of a function, it affects the functions in the block it encloses.

Nested pragmas override the outer ones.

If there are multiple pragmas inside a function, the lexically last one that is semantically analyzed controls the behavior.

If the pragma is versioned out or in a false static if conditional, it is ignored.

If a pragma specifies always inline, and the compiler cannot inline it, a warning will be generated. Implementations will likely vary in their ability to inline.

These are not attributes because they should not affect the semantics of the function. In particular, the function signature must not be affected.

Usage

pragma(inline, true);  // always inline
pragma(inline, false); // never inline
pragma(inline);        // revert to default behavior

Copyright

This document has been placed in the Public Domain.