[LLVMdev] strict aliasing and LLVM

[Chris Lattner]

On Oct 29, 2010, at 11:35 AM, Xinliang David Li wrote:
> Thanks for the -m tip to pass llvm options.  Why is it not documented anywhere. See http://clang.llvm.org/docs/UsersManual.html#commandline

-mllvm flags are somewhat equivalent to gcc -param options.  -mllvm flags are for compiler hackers to play with, and are not stable or documented.  Once TBAA is stable and reliable it will be controlled with -fstrict-aliasing as you'd expect.

-Chris

> 
> David
> 
> On Fri, Oct 29, 2010 at 2:17 AM, Benjamin Kramer <benny.kra at googlemail.com> wrote:
> 
> On 29.10.2010, at 09:26, Nick Lewycky wrote:
> 
> >  * If clang -O2 worked by running 'opt' and 'llc' under the hood, we
> > could tell it to pass a flag along to them, but it doesn't. As it
> > stands, you can't turn -enable-tbaa on when running clang.
> >
> > So, putting that together, one way to do it is:
> >
> >   clang -O2 -fstrict-aliasing foo.c -flto -c -o foo.bc
> >   opt -O2 -enable-tbaa foo.bc foo2.bc
> >   llc -O2 -enable-tbaa foo2.bc -o foo2.s
> 
> clang -O2 foo.c -S -o foo.s -mllvm -enable-tbaa
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