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| -rw-r--r-- | clang/docs/LanguageExtensions.html | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/clang/docs/LanguageExtensions.html b/clang/docs/LanguageExtensions.html index 5b8518b3305..d73e3026b1f 100644 --- a/clang/docs/LanguageExtensions.html +++ b/clang/docs/LanguageExtensions.html @@ -27,6 +27,11 @@ td { <li><a href="#__builtin_shufflevector">__builtin_shufflevector</a></li> </ul> </li> +<li><a href="#targetspecific">Target-Specific Extensions</a> + <ul> + <li><a href="#x86-specific">X86/X86-64 Language Extensions</a></li> + </ul> +</li> </ul> @@ -224,6 +229,45 @@ with the same element type as vec1/vec2 but that has an element count equal to the number of indices specified. </p> +<!-- ======================================================================= --> +<h2 id="targetspecific">Target-Specific Extensions</h2> +<!-- ======================================================================= --> + +<p>Clang supports some language features conditionally on some targets.</p> + +<!-- ======================================================================= --> +<h3 id="x86-specific">X86/X86-64 Language Extensions</h3> +<!-- ======================================================================= --> + +<p>The X86 backend has these language extensions:</p> + +<!-- ======================================================================= --> +<h4 id="x86-gs-segment">Memory references off the GS segment</h4> +<!-- ======================================================================= --> + +<p>Annotating a pointer with address space #256 causes it to be code generated +relative to the X86 GS segment register. +Note that this is a very very low-level feature that should only be used if you +know what you're doing (for example in an OS kernel).</p> + +<p>Here is an example:</p> + +<pre> +#define GS_RELATIVE __attribute__((address_space(256))) +int foo(int GS_RELATIVE *P) { + return *P; +} +</pre> + +<p>Which compiles to (on X86-32):</p> + +<pre> +_foo: + movl 4(%esp), %eax + movl %gs:(%eax), %eax + ret +</pre> + </div> </body> </html> |
