Difference between revisions of "DIP56"
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|Status: | |Status: | ||
| − | | | + | |Preliminarily approved post 2.067 |
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|Created: | |Created: | ||
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|Last Modified: | |Last Modified: | ||
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|Author: | |Author: | ||
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== Abstract == | == Abstract == | ||
| − | This proposal uses pragmas to add | + | This proposal uses pragmas to add inlining instructions to the compiler. |
== Rationale == | == Rationale == | ||
| Line 32: | Line 32: | ||
== Description == | == Description == | ||
| − | + | This adds a pragma 'inline', which is followed by an optional boolean expression, which influences the inlining of the function it appears in. An evaluation of 'true' means always inline, 'false' means never inline, and no argument means the default behavior, as indicated in the command line. | |
| + | |||
| + | 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. | |
| − | |||
| − | These are not attributes because they should not affect the semantics of the function. In particular, the function signature | + | If a pragma specifies always inline, and the compiler cannot inline it, a warning will be generated. |
| − | must not be affected. | + | 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 == | == Usage == | ||
| − | < | + | With the <code>-inline</code> compiler flag: |
| + | |||
| + | pragma(inline, true) always inlines | ||
| + | pragma(inline, false) never inlines | ||
| + | pragma(inline) inlines at compiler's discretion | ||
| − | + | Without the <code>-inline</code> compiler flag: | |
| − | |||
| + | pragma(inline, true) always inlines | ||
| + | pragma(inline, false) never inlines | ||
| + | pragma(inline) never inlines | ||
== Copyright == | == Copyright == | ||
Latest revision as of 00:07, 5 February 2015
| Title: | Provide pragma to control function inlining |
|---|---|
| DIP: | 56 |
| Version: | 0 |
| Status: | Preliminarily approved post 2.067 |
| Created: | 2014-02-23 |
| Last Modified: | 2015-02-04 |
| Author: | Walter Bright |
| Links: |
Contents
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', which is followed by an optional boolean expression, which influences the inlining of the function it appears in. An evaluation of 'true' means always inline, 'false' means never inline, and no argument means the default behavior, as indicated in the command line.
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
With the -inline compiler flag:
pragma(inline, true) always inlines pragma(inline, false) never inlines pragma(inline) inlines at compiler's discretion
Without the -inline compiler flag:
pragma(inline, true) always inlines pragma(inline, false) never inlines pragma(inline) never inlines
Copyright
This document has been placed in the Public Domain.
