Messages in this thread | | | Date | Mon, 27 Jan 2014 17:45:44 +0100 | From | Borislav Petkov <> | Subject | Re: [RFC] x86: Disable traditional FPU instructions too |
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On Mon, Jan 27, 2014 at 08:41:09AM -0800, H. Peter Anvin wrote: > I don't think it'd hurt... although I think the above pretty much > requires that the code contain actual floating-point types to ever be > generated.
Yes, that is supposed to catch usage of the 'E' floating constant, for example, in definitions. It is a build-time assertion, if you want. :)
> The issue with MMX/SSE is that an autovectorizing compiler could > decide to use them for *integer* code.
Right, and we don't want the FPU state handling if it can be helped.
> -mno-fp-ret-in-387 in particular will only ever apply if a function > return type is a floating-point type.
Yeah, this is for when using -msoft-float == -mno-80387 which still can generate FPU insns according to the manpage:
On machines where a function returns floating-point results in the 80387 register stack, some floating-point opcodes may be emitted even if -msoft-float is used.
-- Regards/Gruss, Boris.
Sent from a fat crate under my desk. Formatting is fine. --
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