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fix description of 'ret' to be more correct with multiple return

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values.  Clarify that it is impossible to 'multiply return' a 
struct with zero elements.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50131 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-04-23 04:59:35 +00:00
parent 1c406d77a6
commit f4cde4ec81
1 changed files with 27 additions and 12 deletions
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39
docs/LangRef.html
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@ -1223,17 +1223,21 @@ type "{ i32, [0 x float]}", for example.</p>
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection"> <a name="t_function">Function Type</a> </div>
<div class="doc_text">
<h5>Overview:</h5>
<p>The function type can be thought of as a function signature. It
consists of a return type and a list of formal parameter types. The
return type of a function type is a scalar type or a void type or a struct type.
return type of a function type is a scalar type, a void type, or a struct type.
If the return type is a struct type then all struct elements must be of first
class types. Function types are usually used to build virtual function tables
(which are structures of pointers to functions), for indirect function
calls, and when defining a function.</p>
class types, and the struct must have at least one element.</p>
<h5>Syntax:</h5>
<pre> &lt;returntype list&gt; (&lt;parameter list&gt;)<br></pre>
<pre>
&lt;returntype list&gt; (&lt;parameter list&gt;)
</pre>
<p>...where '<tt>&lt;parameter list&gt;</tt>' is a comma-separated list of type
specifiers. Optionally, the parameter list may include a type <tt>...</tt>,
which indicates that the function takes a variable number of arguments.
@ -1241,6 +1245,7 @@ Variable argument functions can access their arguments with the <a
href="#int_varargs">variable argument handling intrinsic</a> functions.
'<tt>&lt;returntype list&gt;</tt>' is a comma-separated list of
<a href="#t_firstclass">first class</a> type specifiers.</p>
<h5>Examples:</h5>
<table class="layout">
<tr class="layout">
@ -1802,19 +1807,26 @@ Instruction</a> </div>
ret void <i>; Return from void function</i>
ret &lt;type&gt; &lt;value&gt;, &lt;type&gt; &lt;value&gt; <i>; Return two values from a non-void function </i>
</pre>
<h5>Overview:</h5>
<p>The '<tt>ret</tt>' instruction is used to return control flow (and a
value) from a function back to the caller.</p>
<p>There are two forms of the '<tt>ret</tt>' instruction: one that
returns a value and then causes control flow, and one that just causes
returns value(s) and then causes control flow, and one that just causes
control flow to occur.</p>
<h5>Arguments:</h5>
<p>The '<tt>ret</tt>' instruction may return one or multiple values. The
type of each return value must be a '<a href="#t_firstclass">first class</a>'
type. Note that a function is not <a href="#wellformed">well formed</a>
if there exists a '<tt>ret</tt>' instruction inside of the function that
returns values that do not match the return type of the function.</p>
<p>The '<tt>ret</tt>' instruction may return zero, one or multiple values.
The type of each return value must be a '<a href="#t_firstclass">first
class</a>' type. Note that a function is not <a href="#wellformed">well
formed</a> if there exists a '<tt>ret</tt>' instruction inside of the
function that returns values that do not match the return type of the
function.</p>
<h5>Semantics:</h5>
<p>When the '<tt>ret</tt>' instruction is executed, control flow
returns back to the calling function's context. If the caller is a "<a
href="#i_call"><tt>call</tt></a>" instruction, execution continues at
@ -1825,8 +1837,11 @@ returns a value, that value shall set the call or invoke instruction's
return value. If the instruction returns multiple values then these
values can only be accessed through a '<a href="#i_getresult"><tt>getresult</tt>
</a>' instruction.</p>
<h5>Example:</h5>
<pre> ret i32 5 <i>; Return an integer value of 5</i>
<pre>
ret i32 5 <i>; Return an integer value of 5</i>
ret void <i>; Return from a void function</i>
ret i32 4, i8 2 <i>; Return two values 4 and 2 </i>
</pre>