[PATCH] prevent folding a scalar FP load into a packed logical FP instruction (PR22371)

[Sanjay Patel]

In http://reviews.llvm.org/D7474#121658, @qcolombet wrote:

> Unless we hit some read protection error, I do not see why reading undefined memory is a problem 
>  as long as we use only the part that is defined. It seems that is the case in those cases, isn’t it?


Hi Quentin,

I think there is a danger beyond just a read protection error. For example, what if there's a denorm FP value in that extra bit of memory that we were never supposed to load?

See PR20358 ( http://llvm.org/bugs/show_bug.cgi?id=20358 ) for a really bad example of what might happen in that case - 19x perf hit.

Also, I'm not a security expert, but I worry that reading any extra mem is some kind of security violation / potential for hackery?


http://reviews.llvm.org/D7474

EMAIL PREFERENCES
  http://reviews.llvm.org/settings/panel/emailpreferences/