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RE: Implicit altivec vs. linux kernel build
- From: "Dave Korn" <dave dot korn at artimi dot com>
- To: "'David Edelsohn'" <dje at watson dot ibm dot com>,"'Benjamin Herrenschmidt'" <benh at kernel dot crashing dot org>
- Cc: "'Geoff Keating'" <geoffk at geoffk dot org>,<gcc at gcc dot gnu dot org>,"'Paul Mackerras'" <paulus at samba dot org>,"'Alan Modra'" <amodra at bigpond dot net dot au>
- Date: Mon, 28 Feb 2005 14:07:40 -0000
- Subject: RE: Implicit altivec vs. linux kernel build
----Original Message----
>From: gcc-owner On Behalf Of David Edelsohn
>Sent: 27 February 2005 23:35
>> So what is the proper way or set of options for me to:
>
>> 1) optionally have POWER4 optimisations (that must be independant on the
>> rest below) 2) be able to use altivec instructions in assembly
>> 3) be able to use altivec in a few selected bits of C code
>> 4) never have altivec code implicitely generated by the compiler
>
> It sounds like you are making conflicting requests of the
> compiler. You want the compiler to know about VMX registers, have them
> active, use them in inlined assembly, but not have the compiler generate
> VMX instructions itself. If you use the compiler in inconsistent ways,
> you are going to run into trouble.
> You cannot tell the compiler to enable VMX but "do what I mean"
> and not use it. That is inconsistent.
Surely it would be possible to use -ffixed-* options to reserve all the
altivec registers and get precisely that effect?
cheers,
DaveK
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