Split the init.trampoline intrinsic, which currently combines GCC's

init.trampoline and adjust.trampoline intrinsics, into two intrinsics
like in GCC.  While having one combined intrinsic is tempting, it is
not natural because typically the trampoline initialization needs to
be done in one function, and the result of adjust trampoline is needed
in a different (nested) function.  To get around this llvm-gcc hacks the
nested function lowering code to insert an additional parent variable
holding the adjust.trampoline result that can be accessed from the child
function.  Dragonegg doesn't have the luxury of tweaking GCC code, so it
stored the result of adjust.trampoline in the memory GCC set aside for
the trampoline itself (this is always available in the child function),
and set up some new memory (using an alloca) to hold the trampoline.
Unfortunately this breaks Go which allocates trampoline memory on the
heap and wants to use it even after the parent has exited (!).  Rather
than doing even more hacks to get Go working, it seemed best to just use
two intrinsics like in GCC.  Patch mostly by Sanjoy Das.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139140 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 53 insertions, 18 deletions

diff --git a/docs/LangRef.html b/docs/LangRef.html
index 2b9ee24bf4..0ec08eb0a0 100644
--- a/docs/LangRef.html
+++ b/docs/LangRef.html
@@ -275,9 +275,10 @@
       </li>
       <li><a href="#int_debugger">Debugger intrinsics</a></li>
       <li><a href="#int_eh">Exception Handling intrinsics</a></li>
-      <li><a href="#int_trampoline">Trampoline Intrinsic</a>
+      <li><a href="#int_trampoline">Trampoline Intrinsics</a>
         <ol>
           <li><a href="#int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a></li>
+          <li><a href="#int_at">'<tt>llvm.adjust.trampoline</tt>' Intrinsic</a></li>
         </ol>
       </li>
       <li><a href="#int_atomics">Atomic intrinsics</a>
@@ -7680,12 +7681,12 @@ LLVM</a>.</p>
 
 <!-- ======================================================================= -->
 <h3>
-  <a name="int_trampoline">Trampoline Intrinsic</a>
+  <a name="int_trampoline">Trampoline Intrinsics</a>
 </h3>
 
 <div>
 
-<p>This intrinsic makes it possible to excise one parameter, marked with
+<p>These intrinsics make it possible to excise one parameter, marked with
    the <a href="#nest"><tt>nest</tt></a> attribute, from a function.
    The result is a callable
    function pointer lacking the nest parameter - the caller does not need to
@@ -7702,7 +7703,8 @@ LLVM</a>.</p>
 <pre class="doc_code">
   %tramp = alloca [10 x i8], align 4 ; size and alignment only correct for X86
   %tramp1 = getelementptr [10 x i8]* %tramp, i32 0, i32 0
-  %p = call i8* @llvm.init.trampoline(i8* %tramp1, i8* bitcast (i32 (i8*, i32, i32)* @f to i8*), i8* %nval)
+  call i8* @llvm.init.trampoline(i8* %tramp1, i8* bitcast (i32 (i8*, i32, i32)* @f to i8*), i8* %nval)
+  %p = call i8* @llvm.adjust.trampoline(i8* %tramp1)
   %fp = bitcast i8* %p to i32 (i32, i32)*
 </pre>
 
@@ -7720,12 +7722,12 @@ LLVM</a>.</p>
 
 <h5>Syntax:</h5>
 <pre>
-  declare i8* @llvm.init.trampoline(i8* &lt;tramp&gt;, i8* &lt;func&gt;, i8* &lt;nval&gt;)
+  declare void @llvm.init.trampoline(i8* &lt;tramp&gt;, i8* &lt;func&gt;, i8* &lt;nval&gt;)
 </pre>
 
 <h5>Overview:</h5>
-<p>This fills the memory pointed to by <tt>tramp</tt> with code and returns a
-   function pointer suitable for executing it.</p>
+<p>This fills the memory pointed to by <tt>tramp</tt> with executable code,
+   turning it into a trampoline.</p>
 
 <h5>Arguments:</h5>
 <p>The <tt>llvm.init.trampoline</tt> intrinsic takes three arguments, all
@@ -7739,17 +7741,50 @@ LLVM</a>.</p>
 
 <h5>Semantics:</h5>
 <p>The block of memory pointed to by <tt>tramp</tt> is filled with target
-   dependent code, turning it into a function.  A pointer to this function is
-   returned, but needs to be bitcast to an <a href="#int_trampoline">appropriate
-   function pointer type</a> before being called.  The new function's signature
-   is the same as that of <tt>func</tt> with any arguments marked with
-   the <tt>nest</tt> attribute removed.  At most one such <tt>nest</tt> argument
-   is allowed, and it must be of pointer type.  Calling the new function is
-   equivalent to calling <tt>func</tt> with the same argument list, but
-   with <tt>nval</tt> used for the missing <tt>nest</tt> argument.  If, after
-   calling <tt>llvm.init.trampoline</tt>, the memory pointed to
-   by <tt>tramp</tt> is modified, then the effect of any later call to the
-   returned function pointer is undefined.</p>
+   dependent code, turning it into a function.  Then <tt>tramp</tt> needs to be
+   passed to <a href="#int_at">llvm.adjust.trampoline</a> to get a pointer
+   which can be <a href="#int_trampoline">bitcast (to a new function) and
+   called</a>.  The new function's signature is the same as that of
+   <tt>func</tt> with any arguments marked with the <tt>nest</tt> attribute
+   removed.  At most one such <tt>nest</tt> argument is allowed, and it must be of
+   pointer type.  Calling the new function is equivalent to calling <tt>func</tt>
+   with the same argument list, but with <tt>nval</tt> used for the missing
+   <tt>nest</tt> argument.  If, after calling <tt>llvm.init.trampoline</tt>, the
+   memory pointed to by <tt>tramp</tt> is modified, then the effect of any later call
+   to the returned function pointer is undefined.</p>
+</div>
+
+<!-- _______________________________________________________________________ -->
+<h4>
+  <a name="int_at">
+    '<tt>llvm.adjust.trampoline</tt>' Intrinsic
+  </a>
+</h4>
+
+<div>
+
+<h5>Syntax:</h5>
+<pre>
+  declare i8* @llvm.adjust.trampoline(i8* &lt;tramp&gt;)
+</pre>
+
+<h5>Overview:</h5>
+<p>This performs any required machine-specific adjustment to the address of a
+   trampoline (passed as <tt>tramp</tt>).</p>
+
+<h5>Arguments:</h5>
+<p><tt>tramp</tt> must point to a block of memory which already has trampoline code
+   filled in by a previous call to <a href="#int_it"><tt>llvm.init.trampoline</tt>
+   </a>.</p>
+
+<h5>Semantics:</h5>
+<p>On some architectures the address of the code to be executed needs to be
+   different to the address where the trampoline is actually stored.  This
+   intrinsic returns the executable address corresponding to <tt>tramp</tt>
+   after performing the required machine specific adjustments.
+   The pointer returned can then be <a href="#int_trampoline"> bitcast and
+   executed</a>.
+</p>
 
 </div>