On Dec 18, 2012, at 10:31 AM, Peter Bergner <berg...@vnet.ibm.com> wrote:
> On Tue, 2012-12-18 at 07:28 -0600, Jimi Xenidis wrote: >> On Dec 17, 2012, at 6:26 PM, Peter Bergner <berg...@vnet.ibm.com> wrote: >>> Jimi, are you using an "old" binutils from before my patch that >>> changed the operand order for these types of instructions? >>> >>> http://sourceware.org/ml/binutils/2009-02/msg00044.html >> >> Actually, this confused me as well, that embedded has the same instruction >> encoding but different mnemonic. > > The mnemonic is the same (ie, dcbtst), and yes, the encoding is the same. > All that is different is the accepted operand ordering...and yes, it is > very unfortunate the operand ordering is different between embedded and > server. :( > > >> I was under the impression that the assembler made no instruction decisions >> based on CPU. So your only hint would be that '0b' prefix. >> Does AS even see that? > > GAS definitely makes decisions based on CPU (ie, -m<cpu> option). Below is > the GAS code used in recognizing the dcbtst instruction. This shows that > the "server" operand ordering is enabled for POWER4 and later cpus while > the "embedded" operand ordering is enabled for pre POWER4 cpus (yes, not > exactly a server versus embedded trigger, but that's we agreed on to > mitigate breaking any old asm code out there). > > {"dcbtst", X(31,246), X_MASK, POWER4, PPCNONE, {RA0, > RB, CT}}, > {"dcbtst", X(31,246), X_MASK, PPC|PPCVLE, POWER4, {CT, > RA0, RB}}, > > GAS doesn't look at how the operands are written to try and guess what > operand ordering you are attempting to use. Rather, it knows what ordering > it expects and the values had better match that ordering. > I agree, but that means it is impossible for the same .S file can be compiled but -mcpu=e500mc and -mcpu=powerpc? So either these files have to be Book3S versus Book3E --or-- we use a CPP macro to get them right. FWIW, I prefer the latter which allows more code reuse. -jx > > Peter > > > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
