On Fri, 2006-07-21 at 10:09, David Mosberger-Tang wrote: > These are bogus errors in my opinion and should be removed. For > example, we already commonly use "saves" to r0 to terminate the > call-chain. I'm seeing this with gas v2.17, but it may have been > around for longer. This was added by Jan Beulich of Novell on July 1, 2005. He was fixing inconsistencies between gas and ias, while trying to port a large body of code from ias to gas. So both IAS and the Intel Assembler Language Guide say that r0/f0/f1 are not valid registers here. However, the Intel ALG does not prevent saves to r0. It is only spillreg and spillreg.p that aren't allowed to take a readonly register as an operand. There is similar language in the Software Conventions and Run-time Architecure Guide. In Appendix B, Unwind Descriptor Record Format, section B.5, in the Format X2 description, it gives encodings for all registers other than r0/f0/f1. Looking at this, it is clear that r0 is a problem here, because the obvious encoding for r0 is actually used by the restorereg record type. We can't support spillreg for r0, though we could for f0. However, we run the risk that SCRA may someday use the f0 encoding for something else. So it seems unwise to do this. Jim - : send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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