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</o:shapelayout></xml><![endif]--></head><body lang=EN-IE link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>Hi Chris,<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>Can I bring this in a bit closer to Leon - is this specifically to do with 64-bit FP transactions with memory? The reason I ask is that I had similar problems adapting Sparc Leon 3 and 4 which are V8 Sparc, but with 64-bit memory bus transactions with the GCC compiler. It “feels” like the same problem, but LLVM versus GCC. In the GCC case, the 64-bit memory transaction had the register endian ordering the wrong way round; perhaps it is something similar in LLVM?<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>Are you doing this with “sparc” or “sparcel”?<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'>Thanks, MartinO<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Book Antiqua",serif;color:#943634;mso-fareast-language:EN-US'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'>From:</span></b><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> llvm-dev [mailto:llvm-dev-bounces@lists.llvm.org] <b>On Behalf Of </b>Chris.Dewhurst via llvm-dev<br><b>Sent:</b> 19 October 2016 22:27<br><b>To:</b> llvm-dev@lists.llvm.org<br><b>Subject:</b> [llvm-dev] [Sparc] vararg double issue on 32 bit Sparc processors<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'>Hi, <o:p></o:p></span></p><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'>I've discovered a problem on Sparc processors (specifically, LEON, but I suspect but can't verify that it also happens on all Sparc processors).<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'>The problem is, or appears to be with using double values in Sparc (32 bit).<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'>Specifically, double values are not being loaded into registers correctly within a function using va_args. Only half the value is loaded (i.e. 32, rather than 64 bits of the value).<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'>What I have also found is that the failure does not happen in all circumstances. The simplest situation I've been able to re-create that avoids the problem is to put a store and subsequent load instruction around the va_arg instruction that deals with the double value. e.g. (in an .ll file):<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'>This code fragment does not work:<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> define void @foo(i32 %v, i8* %ap) local_unnamed_addr {<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> entry:<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> %ap.addr = alloca i8*, align 4<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> store i8* %ap, i8** %ap.addr, align 4<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> %0 = va_arg i8** %ap.addr, i64<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> %conv = trunc i64 %0 to i32<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> %1 = va_arg i8** %ap.addr, double<o:p></o:p></span></p></div></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> ...<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'>Whereas this nearly identical code fragment, wrapping the store and load around the "double" va_arg instruction does work:<o:p></o:p></span></p></div><div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> define void @foo(i32 %v, i8* %ap) local_unnamed_addr {<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> entry:<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> %ap.addr = alloca i8*, align 4<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> store i8* %ap, i8** %ap.addr, align 4<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> %0 = va_arg i8** %ap.addr, i64<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> %conv = trunc i64 %0 to i32<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> store i32 %conv, i32* @foo_arg, align 4<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> %1 = va_arg i8** %ap.addr, double<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> %2 = load i32, i32* @foo_arg, align 4<o:p></o:p></span></p></div></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'> ...<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'>I had been attempting to make various changes to SparcISelLowering.cpp to try to simulate something similar where the code is output, but I don't feel as though I'm heading in the right direction. I'm still not sure quite where the source of the problem lies.<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'>I can provide more details on specifics, but rather than head off into excessive details immediately, I'd appreciate if anyone can help me identify what direction I really should be taking to fix this problem. I'm not convinced I've been going about it the right way so far.<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'>Chris Dewhurst, Lero, University of Limerick.<o:p></o:p></span></p></div></div></div></body></html>