On Sun, Aug 16, 2015 at 3:05 AM Simon Pilgrim <llvm-...@redking.me.uk> wrote:
> RKSimon added a comment. > > Yes using that uninitialized value has worried me as well. I originally > set it to zero (and considered using __ LINE __ or __ COUNTER __) but both > introduce defined behaviour that I could see causing all sorts of problems > further down the line in debug vs release builds. How undefined do we want > our undefined to be? ;-) > > Yeah, this is why I hadn't implemented them yet either. > I can create __builtin_ia32_undef64mmx / __builtin_ia32_undef128 / > __builtin_ia32_undef256 / __builtin_ia32_undef512 if nobody can think of a > better alternative? > > This seems fairly heavyweight, but I don't have any better ideas. I'll assume we don't want to try to expose undef as a value in C (making it as something we could just add), if not then this seems to make the most sense. It's pretty painful/ugly though. Are people using these or did they just notice for completeness? We probably _could_ define them to zero and leave it at that. It's not pleasant and slower than it needs to be but not crazy. -eric > > Repository: > rL LLVM > > http://reviews.llvm.org/D12052 > > > >
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