<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Jan 15, 2016 at 1:55 PM, Jonathan Roelofs <span dir="ltr"><<a href="mailto:jonathan@codesourcery.com" target="_blank">jonathan@codesourcery.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class=""><br>
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On 1/15/16 2:42 PM, Adrian Prantl wrote:<br>
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On Jan 15, 2016, at 1:29 PM, David Blaikie <<a href="mailto:dblaikie@gmail.com" target="_blank">dblaikie@gmail.com</a><br></span><span class="">
<mailto:<a href="mailto:dblaikie@gmail.com" target="_blank">dblaikie@gmail.com</a>>> wrote:<br>
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On Fri, Jan 15, 2016 at 6:54 AM, Jonathan Roelofs via llvm-commits<br></span><span class="">
<<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.org</a> <mailto:<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.org</a>>> wrote:<br>
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jroelofs added a comment.<br>
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@Dblaikie Not sure if my explanation was clear: I'm trying to<br>
convert the DI metadata from the kind that references a global, to<br>
the kind that references a local.<br>
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Right<br>
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To do that, I /think/ I need to add the dbg.declare/value to the<br>
alloca that gets's created, and delete the one that references the<br>
soon-to-be-dead global. Does /that/ seem to you to be something<br>
out of the range of things that the DI metadata scheme can cope with?<br>
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The problem I'm getting at is that I think you'll end up with DWARF<br>
that doesn't make sense. You'll end up with a local variable instead<br>
of a global. Not just a global described by a local location.<br>
<br>
Does that make sense?<br>
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Ahh, I see. Thanks for the explanation.<span class=""><br>
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DWARF:<br>
<br>
DW_TAG_compile_unit<br>
DW_TAG_global_variable "foo"<br>
DW_TAG_subprogram<br>
DW_TAG_variable "bar"<br>
...<br>
<br>
-><br>
<br>
DW_TAG_compile_unit<br>
DW_TAG_subprogram<br>
DW_TAG_variable "foo"<br>
DW_TAG_variable "bar"<br>
<br>
Which isn't correct. "foo" should still be a DW_TAG_global_variable in<br>
the CU scope, its location should be a local location.<br>
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I don't think the metadata can describe this currently... - but I<br>
could be wrong.<br>
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I don’t think it can, which is why I suggested this hack with the local<br>
variable on IRC yesterday. But, of course, it would be better to fix<br>
LLVM to support the latter.<br>
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Am I understanding correctly that this is a limitation of the IR's representation of it, and not of DWARF?<br></blockquote><div><br></div><div>That's my understanding, yes. I'd check GCC's DWARF representation for situations like this, but I imagine it's plausible.<br><br>I don't have /great/ ideas about how to do this in LLVM's IR representation or IRGen, especially if the global is sunk into more than one function (eg: int i; void f1() { i = 3; ... } void f2() { i = 7; ... })... won't be pretty.<br><br>- Dave</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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Jon<br>
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-- adrian<br>
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If not, do you know how to delete the DIGlobalVariable here? I<br>
started down this rabbit hole because I've got a bug where the<br>
debug info emitted into the asm references the global... which no<br>
longer exists, causing the assembler to barf on it.<br>
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<br>
<a href="http://reviews.llvm.org/D16209" rel="noreferrer" target="_blank">http://reviews.llvm.org/D16209</a><br>
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-- <br>
Jon Roelofs<br>
<a href="mailto:jonathan@codesourcery.com" target="_blank">jonathan@codesourcery.com</a><br>
CodeSourcery / Mentor Embedded<br>
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