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document calling convention extensions

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21753 91177308-0d34-0410-b5e6-96231b3b80d8
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Chris Lattner 2005-05-06 22:57:40 +00:00
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6
docs/BytecodeFormat.html
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@ -1059,7 +1059,11 @@ href="#uint32_vbr">uint32_vbr</a> that describes the function.</p>
</tr>
<tr>
<td><a href="#bit">bit(0-3)</a></td>
<td class="td_left">Reserved for future use. Currently set to 0001.</td>
<td class="td_left">
Encodes the calling convention number of the function. If this number is
zero, this field is followed by a vbr indicating the CC#. Otherwise, the
CC number of the function is the value of this field minus one.
</td>
</tr>
<tr>
<td><a href="#bit">bit(4)</a></td>

179
docs/LangRef.html
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@ -21,6 +21,7 @@
<ol>
<li><a href="#modulestructure">Module Structure</a></li>
<li><a href="#linkage">Linkage Types</a></li>
<li><a href="#callingconv">Calling Conventions</a></li>
<li><a href="#globalvars">Global Variables</a></li>
<li><a href="#functionstructure">Function Structure</a></li>
</ol>
@ -426,6 +427,62 @@ to have any linkage type other than "externally visible".</a></p>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="callingconv">Calling Conventions</a>
</div>
<div class="doc_text">
<p>LLVM <a href="#functionstructure">functions</a>, <a href="#i_call">calls</a>
and <a href="#i_invoke">invokes</a> can all have an optional calling convention
specified for the call. The calling convention of any pair of dynamic
caller/callee must match, or the behavior of the program is undefined. The
following calling conventions are supported by LLVM, and more may be added in
the future:</p>
<dl>
<dt><b>"<tt>ccc</tt>" - The C calling convention</b>:</dt>
<dd>This calling convention (the default if no other calling convention is
specified) matches the target C calling conventions. This calling convention
supports varargs function calls, and tolerates some mismatch in the declared
prototype and implemented declaration of the function (as does normal C).
</dd>
<dt><b>"<tt>fastcc</tt>" - The fast calling convention</b>:</dt>
<dd>This calling convention attempts to make calls as fast as possible
(e.g. by passing things in registers). This calling convention allows the
target to use whatever tricks it wants to produce fast code for the target,
without having to conform to an externally specified ABI. This calling
convention does not support varargs and requires the prototype of all callees
to exactly match the prototype of the function definition.
</dd>
<dt><b>"<tt>coldcc</tt>" - The cold calling convention</b>:</dt>
<dd>This calling convention attempts to make code in the caller as efficient
as possible under the assumption that the call is not commonly executed. As
such, these calls often preserve all registers so that the call does not break
any live ranges in the caller side. This calling convention does not support
varargs and requires the prototype of all callees to exactly match the
prototype of the function definition.
</dd>
<dt><b>"<tt>cc &lt;<it>n</it>&gt;</tt>" - Numbered convention</b>:</dt>
<dd>Any calling convention may be specified by number, allowing
target-specific calling conventions to be used. Target specific calling
conventions start at 64.
</dd>
<p>More calling conventions can be added/defined on an as-needed basis, to
support pascal conventions or any other well-known target-independent
convention.</p>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="globalvars">Global Variables</a>
@ -466,10 +523,13 @@ accessed through pointers.</p>
<div class="doc_text">
<p>LLVM function definitions are composed of a (possibly empty) argument list,
an opening curly brace, a list of basic blocks, and a closing curly brace. LLVM
function declarations are defined with the "<tt>declare</tt>" keyword, a
function name, and a function signature.</p>
<p>LLVM function definitions consist of an optional <a href="#linkage">linkage
type</a>, an optional <a href="#callingconv">calling convention</a>, a return
type, a function name, a (possibly empty) argument list, an opening curly brace,
a list of basic blocks, and a closing curly brace. LLVM function declarations
are defined with the "<tt>declare</tt>" keyword, an optional <a
href="#callingconv">calling convention</a>, a return type, a function name, and
a possibly empty list of arguments.</p>
<p>A function definition contains a list of basic blocks, forming the CFG for
the function. Each basic block may optionally start with a label (giving the
@ -1154,51 +1214,82 @@ branches or with a lookup table.</p>
uint 2, label %ontwo ]
</pre>
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection"> <a name="i_invoke">'<tt>invoke</tt>'
Instruction</a> </div>
<div class="doc_subsubsection">
<a name="i_invoke">'<tt>invoke</tt>' Instruction</a>
</div>
<div class="doc_text">
<h5>Syntax:</h5>
<pre> &lt;result&gt; = invoke &lt;ptr to function ty&gt; %&lt;function ptr val&gt;(&lt;function args&gt;)<br> to label &lt;normal label&gt; except label &lt;exception label&gt;<br></pre>
<pre>
&lt;result&gt; = invoke [<a href="#callingconv">cconv</a>] &lt;ptr to function ty&gt; %&lt;function ptr val&gt;(&lt;function args&gt;)
to label &lt;normal label&gt; except label &lt;exception label&gt;
</pre>
<h5>Overview:</h5>
<p>The '<tt>invoke</tt>' instruction causes control to transfer to a
specified function, with the possibility of control flow transfer to
either the '<tt>normal</tt>' <tt>label</tt> label or the '<tt>exception</tt>'<tt>label</tt>.
If the callee function returns with the "<tt><a href="#i_ret">ret</a></tt>"
instruction, control flow will return to the "normal" label. If the
callee (or any indirect callees) returns with the "<a href="#i_unwind"><tt>unwind</tt></a>"
instruction, control is interrupted, and continued at the dynamically
nearest "except" label.</p>
<p>The '<tt>invoke</tt>' instruction causes control to transfer to a specified
function, with the possibility of control flow transfer to either the
'<tt>normal</tt>' <tt>label</tt> label or the
'<tt>exception</tt>'<tt>label</tt>. If the callee function returns with the
"<tt><a href="#i_ret">ret</a></tt>" instruction, control flow will return to the
"normal" label. If the callee (or any indirect callees) returns with the "<a
href="#i_unwind"><tt>unwind</tt></a>" instruction, control is interrupted, and
continued at the dynamically nearest "except" label.</p>
<h5>Arguments:</h5>
<p>This instruction requires several arguments:</p>
<ol>
<li>'<tt>ptr to function ty</tt>': shall be the signature of the
pointer to function value being invoked. In most cases, this is a
direct function invocation, but indirect <tt>invoke</tt>s are just as
possible, branching off an arbitrary pointer to function value. </li>
<li>'<tt>function ptr val</tt>': An LLVM value containing a pointer
to a function to be invoked. </li>
<li>'<tt>function args</tt>': argument list whose types match the
function signature argument types. If the function signature indicates
the function accepts a variable number of arguments, the extra
arguments can be specified. </li>
<li>'<tt>normal label</tt>': the label reached when the called
function executes a '<tt><a href="#i_ret">ret</a></tt>' instruction. </li>
<li>'<tt>exception label</tt>': the label reached when a callee
returns with the <a href="#i_unwind"><tt>unwind</tt></a> instruction. </li>
<li>
<p>The optional "cconv" marker indicates which <a href="callingconv">calling
convention</a> the call should use. If none is specified, the call defaults
to using C calling conventions.
</li>
<li>'<tt>ptr to function ty</tt>': shall be the signature of the pointer to
function value being invoked. In most cases, this is a direct function
invocation, but indirect <tt>invoke</tt>s are just as possible, branching off
an arbitrary pointer to function value.
</li>
<li>'<tt>function ptr val</tt>': An LLVM value containing a pointer to a
function to be invoked. </li>
<li>'<tt>function args</tt>': argument list whose types match the function
signature argument types. If the function signature indicates the function
accepts a variable number of arguments, the extra arguments can be
specified. </li>
<li>'<tt>normal label</tt>': the label reached when the called function
executes a '<tt><a href="#i_ret">ret</a></tt>' instruction. </li>
<li>'<tt>exception label</tt>': the label reached when a callee returns with
the <a href="#i_unwind"><tt>unwind</tt></a> instruction. </li>
</ol>
<h5>Semantics:</h5>
<p>This instruction is designed to operate as a standard '<tt><a
href="#i_call">call</a></tt>' instruction in most regards. The
primary difference is that it establishes an association with a label,
which is used by the runtime library to unwind the stack.</p>
<p>This instruction is used in languages with destructors to ensure
that proper cleanup is performed in the case of either a <tt>longjmp</tt>
or a thrown exception. Additionally, this is important for
implementation of '<tt>catch</tt>' clauses in high-level languages that
support them.</p>
href="#i_call">call</a></tt>' instruction in most regards. The primary
difference is that it establishes an association with a label, which is used by
the runtime library to unwind the stack.</p>
<p>This instruction is used in languages with destructors to ensure that proper
cleanup is performed in the case of either a <tt>longjmp</tt> or a thrown
exception. Additionally, this is important for implementation of
'<tt>catch</tt>' clauses in high-level languages that support them.</p>
<h5>Example:</h5>
<pre> %retval = invoke int %Test(int 15)<br> to label %Continue<br> except label %TestCleanup <i>; {int}:retval set</i>
<pre>
%retval = invoke int %Test(int 15) to label %Continue
except label %TestCleanup <i>; {int}:retval set</i>
%retval = invoke <a href="#callingconv">coldcc</a> int %Test(int 15) to label %Continue
except label %TestCleanup <i>; {int}:retval set</i>
</pre>
</div>
@ -2049,7 +2140,7 @@ value argument, otherwise it returns the second value argument.
<h5>Syntax:</h5>
<pre>
&lt;result&gt; = [tail] call &lt;ty&gt;* &lt;fnptrval&gt;(&lt;param list&gt;)
&lt;result&gt; = [tail] call [<a href="#callingconv">cconv</a>] &lt;ty&gt;* &lt;fnptrval&gt;(&lt;param list&gt;)
</pre>
<h5>Overview:</h5>
@ -2062,12 +2153,17 @@ value argument, otherwise it returns the second value argument.
<ol>
<li>
<p>The "tail" marker indicates whether the callee function accesses any
allocas or varargs in the caller. If the "tail" marker is present, the
<p>The optional "tail" marker indicates whether the callee function accesses
any allocas or varargs in the caller. If the "tail" marker is present, the
function call is eligible for tail call optimization. Note that calls may
be marked "tail" even if they do not occur before a <a
href="#i_ret"><tt>ret</tt></a> instruction.
</li>
<li>
<p>The optional "cconv" marker indicates which <a href="callingconv">calling
convention</a> the call should use. If none is specified, the call defaults
to using C calling conventions.
</li>
<li>
<p>'<tt>ty</tt>': shall be the signature of the pointer to function value
being invoked. The argument types must match the types implied by this
@ -2104,6 +2200,7 @@ the <a href="#i_invoke">invoke</a> instruction.</p>
%retval = call int %test(int %argc)
call int(sbyte*, ...) *%printf(sbyte* %msg, int 12, sbyte 42);
%X = tail call int %foo()
%Y = tail call <a href="#callingconv">fastcc</a> int %foo()
</pre>
</div>