Re: LLVM/GCC Integration Proposal

["Joseph S. Myers" <joseph at codesourcery dot com>]

On Fri, 18 Nov 2005, Chris Lattner wrote:

> 1. The build system is taught about C++ code.

With toplevel bootstrap this will bootstrap libstdc++ so that the compiler 
ends up linked with the new libstdc++ not the (in general 
ABI-incompatible) old one?  (This question applies to all projects 
involving C++ in GCC.)

> While it has many virtues, LLVM is still not complete, and we are investing in
> adding the missing features.  In particular, this system is missing two key
> features to be truly useful: debug info support and inline asm support.  Apple
> is currently investing in adding both these features, as well as adding vector
> support.

What (on any one target of your choice) is the GCC testsuite status when 
LLVM-enabled, compared to that without LLVM, and are most of the 
regressions fixed by the addition of debug info, inline asm and vector 
support?  (Once debug info support is added, the same question applies 
regarding GDB testsuite status.)

Do you propose annotating testcases for features not supported with LLVM 
so they are XFAILed when configured with --enable-llvm?  (XFAIL would be 
right for features the compiler should support but LLVM doesn't yet; 
UNSUPPORTED for tests of some incidental feature of the current back-end 
implementation which it makes sense for replacement infrastructure not to 
support.  A switch to LLVM as the default back-end for a target would 
require no such XFAILs for that target, though there might be 
UNSUPPORTEDs, buggy testcases might be fixed or removed and features might 
be removed through the usual deprecation process.  dg-xfail-if and 
dg-skip-if with an llvm effective-target keyword are the way to annotate 
the tests.)

-- 
Joseph S. Myers               http://www.srcf.ucam.org/~jsm28/gcc/
    jsm@polyomino.org.uk (personal mail)
    joseph@codesourcery.com (CodeSourcery mail)
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