Re: [Tinycc-devel] ARM hardfloat prolog
On Thu, May 02, 2013 at 01:02:19PM +0200, Thomas Preud'homme wrote: Do you know where big-endian is used and by who? There once was a port of Debian for ARM big endian but it never got much traction so it seems to me there is not much interest for such a port anyway. No, I don't think I've seen a big endian ARM running Linux or BSD. But I know that there are TMS570 Cortex-R4 hard wired to big endian. Daniel ___ Tinycc-devel mailing list Tinycc-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/tinycc-devel
[Tinycc-devel] ARM hardfloat prolog
Hi Thomas, I saw that you used the following line to store the floating point arguments that have been passed in fpu register: o(0xED2D0A00|nf); /* save s0-s15 on stack if needed */ In my 2nd edition ARM ARM this maps to the FSTMS instruction and there is a note allowing implementations to keep the values in an internal representation and just convert them to IEEE format for storing to memory. So I don't think we can use this instruction to store double arguments and need one FSTMS/FSTMD for each run of consecutive fpu registers of same precision to be stored. Or have read otherwise? Best regards, Daniel ___ Tinycc-devel mailing list Tinycc-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/tinycc-devel
Re: [Tinycc-devel] ARM hardfloat prolog
Le mercredi 1 mai 2013 16:59:25, Daniel Glöckner a écrit : Hi Thomas, I saw that you used the following line to store the floating point arguments that have been passed in fpu register: o(0xED2D0A00|nf); /* save s0-s15 on stack if needed */ In my 2nd edition ARM ARM this maps to the FSTMS instruction and there is a note allowing implementations to keep the values in an internal representation and just convert them to IEEE format for storing to memory. So I don't think we can use this instruction to store double arguments and need one FSTMS/FSTMD for each run of consecutive fpu registers of same precision to be stored. Or have read otherwise? Nope, I didn't see that line. Please go ahead if you want to fix it, otherwise I'll do it later (I'm working right now). Best regards, Daniel Best regards, Thomas signature.asc Description: This is a digitally signed message part. ___ Tinycc-devel mailing list Tinycc-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/tinycc-devel
Re: [Tinycc-devel] ARM hardfloat prolog
On Wed, May 01, 2013 at 05:02:54PM +0200, Thomas Preud'homme wrote: Le mercredi 1 mai 2013 16:59:25, Daniel Glöckner a écrit : In my 2nd edition ARM ARM this maps to the FSTMS instruction and there is a note allowing implementations to keep the values in an internal representation and just convert them to IEEE format for storing to memory. So I don't think we can use this instruction to store double arguments and need one FSTMS/FSTMD for each run of consecutive fpu registers of same precision to be stored. Or have read otherwise? Nope, I didn't see that line. Please go ahead if you want to fix it, otherwise I'll do it later (I'm working right now). I did some more research. ARM ARM 2nd edition (= Issue E) has several paragraphs below figure 2-1 in chapter C2 talking about that no assumptions can be made as to how single-precision registers overlap double-precision registers and that the value of double-precision registers after their corresponding single- precision registers have been loaded with a value becomes UNPREDICTABLE. Issue I, which can be downloaded after registering with ARM, replaces that half page of text with The mapping between a double-precision register and its pair of single-precision registers is as follows: - S2n lies in the least significant half of Dn - S2n+1 lies in the most significant half of Dn. So we are safe with the current implementation, at least on little-endian ARM. On big-endian ARM the halves will have the wrong order if we don't use FSTMD, but there is a lot more that needs to be done until we support big-endian ARM. Daniel ___ Tinycc-devel mailing list Tinycc-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/tinycc-devel
