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Hi Daniel,<br>
<br>
Thanks for the reply. If I understand correctly, your suggestion is to
have the backend call a library that handles the built-in functions.
Would the calls need to be lowered and redirected (e.g. by a big switch
statement or a jump table) to the corresponding function in the library?<br>
<br>
Thanks,<br>
Javier<br>
<br>
On 7/20/2009 12:11 AM, Daniel Dunbar wrote:
<blockquote
cite="mid:6a8523d60907200011wa53fcfbt24c5043f792d907c@mail.gmail.com"
type="cite">
<pre wrap="">Hi Javier,
I'm not the right person to answer your question, but since no one
else took it: I believe this is a situation where the backend would
typically emit a call the the compiler's runtime library (e.g.,
libgcc).
While it isn't currently completely wired up, we do have our own
compiler runtime library available under the compiler-rt project in
the LLVM repo.
- Daniel
On Thu, Jul 16, 2009 at 2:07 AM, Javier Martinez<a class="moz-txt-link-rfc2396E" href="mailto:javier@jmartinez.org"><javier@jmartinez.org></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Hi,
I'm trying to add support in my back end for certain functions that are
seen as built-in by the target. Some of these functions can be
implemented in a) LLVM, and some in b) the native target language.
My approach to case a) is to write the built-in function implementation
in C, compile it to LLVM using Clang, link it to the module that uses it
and finally add a pass to inline it. The last two steps can be made
inside a ModulePass. The definition of TargetMachine allows for any pass
manager deriving form BasicPass to be passed to AddPassesToEmitFile.
However, I see that llc uses a FunctionPassManager for all the passes. A
(module)PassManager is used only if the target implements
AddPassesToEmitWholeFile but the comments on the base class discourage
this path. Am I approaching the problem the wrong way?
I haven't worked much on case b) but my idea was to use a similar
approach but instead of writing the built-in function implementation in
straight C an asm block would be used to insert the code. Does this make
sense?
Thanks,
Javier
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