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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Hi Renato,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>It seems to me that LLVM doesn’t parse the inline asm body. It just checks the constraints, (ie. Input/output interface). During ASM writing, it then binding those constraints to placeholders like %0, %1. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>So it a constraint is a 64-integer type, it *<b>probably</b>* needs paired GPR.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Weiming<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation</span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Renato Golin [mailto:renato.golin@linaro.org] <br><b>Sent:</b> Wednesday, March 13, 2013 10:03 AM<br><b>To:</b> Måns Rullgård<br><b>Cc:</b> LLVM Dev; weimingz@codeaurora.org<br><b>Subject:</b> Re: Problems with 64-bit register operands of inline asm on ARM<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>On 13 March 2013 13:43, Måns Rullgård <<a href="mailto:mans@mansr.com" target="_blank">mans@mansr.com</a>> wrote:<o:p></o:p></p><div><div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><p class=MsoNormal>One possible fix, which I have tested, is to look for the specific<br>instructions requiring such a pair (LDRD/STRD and LDREXD/STREXD) in<br>addition to the 'H' modifier. However, there are probably other<br>creative ways in which inline asm might rely on the specific pairing.<o:p></o:p></p></blockquote><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Hi Mans,<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Either that method is ignoring an inline asm parser or there isn't one, but I agree, we should be able to have something better than just grep for possible extensions for paired registers.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><p class=MsoNormal>Thus I believe the safest solution is to always force 64-bit operands<br>into even/odd pairs for any inline asm. In other words, we should<br>probably do something like this (untested):<o:p></o:p></p></blockquote><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>I tested this, and it fails on other inline assembly tests. I think that the non-paired asm is correctly selected by the table generated parser, but when you pair things that didn't need pairing, the parser goes bad.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>I don't think we should force pairing on every inline assembly either. Maybe someone knows how to parse inline assembly in a better way than it is currently being done? If there isn't any, than possibly creating a function to return "needsPairedRegister()" or something would still be ugly, but better than incrementing it inline.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>cheers,<o:p></o:p></p></div><div><p class=MsoNormal>--renato<o:p></o:p></p></div></div></div></div></div></body></html>