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| author | Andrew Lenharth <andrewl@lenharth.org> | 2005-11-11 16:47:30 +0000 |
|---|---|---|
| committer | Andrew Lenharth <andrewl@lenharth.org> | 2005-11-11 16:47:30 +0000 |
| commit | 51b8d54922350b7e1c2cd5a5183ef2c5f5d1b1d5 (patch) | |
| tree | 76fbb3c458648bcc22897b27ad74c94b13bdc4ff /docs/LangRef.html | |
| parent | aeef8fc5c6124a34bd2a723071a3982b559c26f2 (diff) | |
| download | llvm-51b8d54922350b7e1c2cd5a5183ef2c5f5d1b1d5.tar.gz llvm-51b8d54922350b7e1c2cd5a5183ef2c5f5d1b1d5.tar.bz2 llvm-51b8d54922350b7e1c2cd5a5183ef2c5f5d1b1d5.tar.xz | |
continued readcyclecounter support
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24300 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'docs/LangRef.html')
| -rw-r--r-- | docs/LangRef.html | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/docs/LangRef.html b/docs/LangRef.html index 72dfd88c1b..dd02a9e4a2 100644 --- a/docs/LangRef.html +++ b/docs/LangRef.html @@ -128,6 +128,7 @@ <li><a href="#i_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a></li> <li><a href="#i_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a></li> <li><a href="#i_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a></li> + <li><a href="#i_readcyclecounter"><tt>llvm.readcyclecounter</tt>' Intrinsic</a></li> </ol> </li> <li><a href="#int_os">Operating System Intrinsics</a> @@ -2811,6 +2812,39 @@ support this intrinisic may ignore it. </div> +<!-- _______________________________________________________________________ --> +<div class="doc_subsubsection"> + <a name="i_readcyclecounter">'<tt>llvm.readcyclecounter</tt>' Intrinsic</a> +</div> + +<div class="doc_text"> + +<h5>Syntax:</h5> +<pre> + declare ulong %llvm.readcyclecounter( ) +</pre> + +<h5>Overview:</h5> + + +<p> +The '<tt>llvm.readcyclecounter</tt>' intrinsic provides access to the cycle +counter register (or similar low latency, high accuracy clocks) on those targets +that support it. On X86, it should map to RDTSC. On Alpha, it should map to RPCC. +As the backing counters overflow quickly (on the order of 9 seconds on alpha), this +should only be used for small timings. +</p> + +<h5>Semantics:</h5> + +<p> +When directly supported, reading the cycle counter should not modify any memory. +Implementations are allowed to either return a application specific value or a +system wide value. On backends without support, this is lowered to a constant 0. +</p> + +</div> + <!-- ======================================================================= --> <div class="doc_subsection"> |