<div dir="ltr">struct types and DITypes aren't 1:1 - the same struct type might be used for many DITypes and a single variable (with a single DIType) might be described by multiple different pieces of memory/registers with different struct types throughout its lifetime.<br><br>The nontrivial mapping from debug info to IR is the only real mapping, unfortunately. There's no shortcut.<br><br>- Dave</div><br><div class="gmail_quote"><div dir="ltr">On Tue, Jul 24, 2018 at 11:00 AM Troy Johnson via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<p style="margin-top:0;margin-bottom:0">Right, a GlobalVariable actually has interesting debug metadata attached, but if one is dealing with the target type of a pointer operand of a GEP that's accessing a structure field, then tracing that back to something
with debug metadata is nontrivial. It may not be a GlobalVariable.<br>
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<p style="margin-top:0;margin-bottom:0">-Troy<br>
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<div id="m_-8955959805735291822divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> <a href="mailto:paul.robinson@sony.com" target="_blank">paul.robinson@sony.com</a> <<a href="mailto:paul.robinson@sony.com" target="_blank">paul.robinson@sony.com</a>><br>
<b>Sent:</b> Tuesday, July 24, 2018 12:54:57 PM<br>
<b>To:</b> Troy Johnson<br>
<b>Cc:</b> <a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a><br>
<b>Subject:</b> RE: StructType --> DICompositeType?</font>
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<p class="m_-8955959805735291822x_MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">They aren't directly tied together, as a type by its lonesome isn't all that interesting to either compilers or debuggers.</span></p>
<p class="m_-8955959805735291822x_MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">But for example a global variable has a link to its DIGlobalVariable, which has a link to its DIType, and so you can associate the variable's Type with
a DIType that way.</span></p>
<p class="m_-8955959805735291822x_MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">--paulr</span></p>
<p class="m_-8955959805735291822x_MsoNormal"><a name="m_-8955959805735291822_x__MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></a></p>
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<p class="m_-8955959805735291822x_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""> llvm-dev [mailto:<a href="mailto:llvm-dev-bounces@lists.llvm.org" target="_blank">llvm-dev-bounces@lists.llvm.org</a>]
<b>On Behalf Of </b>Troy Johnson via llvm-dev<br>
<b>Sent:</b> Tuesday, July 24, 2018 11:50 AM<br>
<b>To:</b> <a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a><br>
<b>Subject:</b> [llvm-dev] StructType --> DICompositeType?</span></p>
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<p><span style="font-family:"Calibri","sans-serif";color:black">Is there a more convenient way to obtain a DIType given a Type than matching up the strings for the names?</span></p>
<p><span style="font-family:"Calibri","sans-serif";color:black"> </span></p>
<p><span style="font-family:"Calibri","sans-serif";color:black">For example, given:</span></p>
<p><span style="font-family:"Calibri","sans-serif";color:black"> </span></p>
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<p class="m_-8955959805735291822x_MsoNormal"><span style="font-family:"Calibri","sans-serif";color:black">struct S {<br>
int x, y;<br>
} s;<br>
<br>
void foo(S *a) {<br>
a->x = 0;<br>
a->y = 1;<br>
}</span></p>
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<p><span style="font-family:"Calibri","sans-serif";color:black"> </span></p>
<p><span style="font-family:"Calibri","sans-serif";color:black">There are DIType nodes for the struct Type:</span></p>
<p><span style="font-family:"Calibri","sans-serif";color:black"> </span></p>
<div>
<p class="m_-8955959805735291822x_MsoNormal"><span style="font-family:"Calibri","sans-serif";color:black">!6 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "S", file: !3, line: 1, size: 64, flags: DIFlagTypePassByValue, elements: !7, identifier: "_ZTS1S")<br>
!7 = !{!8, !10}<br>
!8 = !DIDerivedType(tag: DW_TAG_member, name: "x", scope: !6, file: !3, line: 2, baseType: !9, size: 32)<br>
!9 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)<br>
!10 = !DIDerivedType(tag: DW_TAG_member, name: "y", scope: !6, file: !3, line: 2, baseType: !9, size: 32, offset: 32)</span></p>
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<p class="m_-8955959805735291822x_MsoNormal"><span style="font-family:"Calibri","sans-serif";color:black"> </span></p>
<p><span style="font-family:"Calibri","sans-serif";color:black">but given just the StructType for S there is no direct way to get to the DICompositeType. I've made something work by prescanning all the DITypes in my Module and creating a map that uses type
names as the key, being careful to strip "struct." prefixes and maintain scoping for nested structs (e.g., S1::S2), which works, but seems awfully complicated to need to do.</span></p>
<p><span style="font-family:"Calibri","sans-serif";color:black"> </span></p>
<p><span style="font-family:"Calibri","sans-serif";color:black">Seems like StructType should have a getMetaData() function, but I don't see one.</span></p>
<p><span style="font-family:"Calibri","sans-serif";color:black"> </span></p>
<p><span style="font-family:"Calibri","sans-serif";color:black">-Troy</span></p>
<p><span style="font-family:"Calibri","sans-serif";color:black"> </span></p>
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