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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Thinking about it a bit more, I don’t see why it ought to be illegal for the first non-frame-setup instruction to be a CFI directive.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I’m not sure there are any examples except GNU_ARGS_SIZE – but I don’t think it makes sense to special-case it.<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’ve removed the assert in r249668.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Adrian, are you ok with that?
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Michael<o:p></o:p></span></p>
<p class="MsoNormal"><a name="_MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></a></p>
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<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""> friss@apple.com [mailto:friss@apple.com]
<br>
<b>Sent:</b> Thursday, October 08, 2015 06:14<br>
<b>To:</b> Douglas Katzman<br>
<b>Cc:</b> Kuperstein, Michael M; llvm-commits@lists.llvm.org; Adrian Prantl; David Blaikie; Eric Christopher<br>
<b>Subject:</b> Re: [llvm] r249522 - [X86] Emit .cfi_escape GNU_ARGS_SIZE when adjusting the stack before calls<o:p></o:p></span></p>
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<p class="MsoNormal">On Oct 7, 2015, at 6:59 PM, Douglas Katzman <<a href="mailto:dougk@google.com">dougk@google.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">Do you happen to have a testcase handy?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">The sanitizers on Linux comprise a test case it seems - they started failing with this commit.<o:p></o:p></p>
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<p class="MsoNormal"><a href="http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux/builds/20647">http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux/builds/20647</a> <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Without my understanding this code in the least, if you just do what the assertion says to do (as here), it fixes the sanitizers:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">diff --git a/lib/Target/X86/X86FrameLowering.cpp b/lib/Target/X86/X86FrameLowering.cpp<o:p></o:p></p>
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<p class="MsoNormal">index 7f05e5b..d85b6a8 100644<o:p></o:p></p>
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<p class="MsoNormal">--- a/lib/Target/X86/X86FrameLowering.cpp<o:p></o:p></p>
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<p class="MsoNormal">+++ b/lib/Target/X86/X86FrameLowering.cpp<o:p></o:p></p>
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<p class="MsoNormal">@@ -384,8 +384,9 @@ void X86FrameLowering::BuildCFI(MachineBasicBlock &MBB,<o:p></o:p></p>
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<p class="MsoNormal"> MCCFIInstruction CFIInst) const {<o:p></o:p></p>
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<p class="MsoNormal"> MachineFunction &MF = *MBB.getParent();<o:p></o:p></p>
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<p class="MsoNormal"> unsigned CFIIndex = MF.getMMI().addFrameInst(CFIInst);<o:p></o:p></p>
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<p class="MsoNormal">- BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))<o:p></o:p></p>
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<p class="MsoNormal">- .addCFIIndex(CFIIndex);<o:p></o:p></p>
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<p class="MsoNormal">+ MachineInstrBuilder MIB = BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::CFI_INSTRUCTION));<o:p></o:p></p>
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<p class="MsoNormal">+ MIB.addCFIIndex(CFIIndex);<o:p></o:p></p>
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<p class="MsoNormal">+ MIB->setFlag(MachineInstr::FrameSetup);<o:p></o:p></p>
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<p class="MsoNormal"> } <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">This will fix the assert, but I think it is conceptually wrong. FrameSetup is supposed to describe the prologue. This will insert this flag on instructions all over the function. I can’t think of any bad consequences though. CC:ing some
other people with debug info knowledge.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Fred<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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