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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 Jackob,<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'>Thanks for the helpful reply. The bug I encountered caused the DBG_VALUE instructions not to be written back with references to the correct registers/spills… (unless I kept the DBG_VALUE for the corner-case I described in the bug)<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'>What happened in when reading the DWARF I couldn’t see that variable associated with its register, a dump of the output assembly/sections/..etc showed that the variable is not in the “.section .debug_info”. <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'>I found the problem on AMD’s OpenCL Compiler (<a href="http://llvm.org/devmtg/2010-11/Villmow-OpenCL.pdf">http://llvm.org/devmtg/2010-11/Villmow-OpenCL.pdf</a> ) on the AMDIL Codegen backend (slide 3), Unfortunately I wasn’t able to reproduce it with other backbends (x86) that have much less physical registers/more spills.<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'>Regards,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>---Yousef<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><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><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"'> Jakob Stoklund Olesen [mailto:stoklund@2pi.dk] <br><b>Sent:</b> Sunday, June 12, 2011 8:45 PM<br><b>To:</b> Shajrawi, Yousef<br><b>Cc:</b> llvm-commits@cs.uiuc.edu; Villmow, Micah<br><b>Subject:</b> Re: [llvm-commits] patch for Bug #10125<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal>On Jun 12, 2011, at 12:50 AM, Shajrawi, Yousef wrote:<o:p></o:p></p></div><p class=MsoNormal><br><br><o:p></o:p></p><div><div><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>I’ve reported bug #10125 about debug variables incorrectly deleted by LLVM in the Live Debug Variables pass: <a href="http://llvm.org/bugs/show_bug.cgi?id=10125">http://llvm.org/bugs/show_bug.cgi?id=10125</a><o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> <o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>Attached is a patch resolving this bug via adding a check to live ins of a basic block (description is in bugzilla)<o:p></o:p></span></p></div></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Hi Yousef,<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>I think you are misunderstanding the purpose of the Live Debug Variables pass. It is supposed to remove all DBG_VALUE instructions. It builds a data structure that is easier to work with for the register allocator passes.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>After register allocation, the DBG_VALUE instructions are written back with references to the correct physical registers and spill slots.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>This is all necessary to keep track of debug variables while the register allocator coalesces and splits and spills live ranges.<o:p></o:p></p></div><p class=MsoNormal><br><br><o:p></o:p></p><div><div><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> Please see if this is suitable for adding to LLVM and/or please advise on what to do next, This is my first contribution to LLVM so I don’t know the procedure…<o:p></o:p></span></p></div></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>You are on the right track, but please make sure that you describe the actual symptoms when you file a bug report. The behavior you describe sounds correct to me, and when I run your IR through the ARM backend, the result looks fine.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>So what caused you to file a bug in the first place?<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>/jakob<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div></div></div></body></html>