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<p class="MsoNormal">I don’t see any use of DW_TAG_constant in the LLVM tree, except in the DWARFLinker, which isn’t what you need.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Most things not needed by C-family languages aren’t supported, because to date nobody has needed them (or if they did, they implemented the support downstream). The closest similar thing would be enumerator constants; you could probably
imitate what’s done for those fairly easily.<o:p></o:p></p>
<p class="MsoNormal">--paulr<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>From:</b> llvm-dev <llvm-dev-bounces@lists.llvm.org> <b>On Behalf Of
</b>Tomar, Sourabh Singh via llvm-dev<br>
<b>Sent:</b> Wednesday, February 10, 2021 12:54 AM<br>
<b>To:</b> llvm-dev <llvm-dev@lists.llvm.org><br>
<b>Cc:</b> George, Jini Susan <JiniSusan.George@amd.com>; Chen, Chih-Ping <chih-ping.chen@intel.com>; Sharma, Alok Kumar <AlokKumar.Sharma@amd.com><br>
<b>Subject:</b> [llvm-dev] [DebugInfo]: Representing constants in debug-info<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="msipheader87abd423" style="margin:0in"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#317100">[AMD Public Use]</span><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hi Everyone,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Is there a way of representing **constants** in LLVM debug-info ? Languages such as FORTRAN has constants<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">i.e, consider the following Fortran snippet<o:p></o:p></p>
<p class="MsoNormal">[…]<o:p></o:p></p>
<p class="MsoNormal">Module foo<o:p></o:p></p>
<p class="MsoNormal">Integer, parameter :: bar = 200 ! Constant<o:p></o:p></p>
<p class="MsoNormal">End module foo<o:p></o:p></p>
<p class="MsoNormal">[…]<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">A front-end may choose to emit as Global Constant in LLVM IR as:<o:p></o:p></p>
<p class="MsoNormal">[…]<o:p></o:p></p>
<p class="MsoNormal">@bar.. = internal constant i32 200<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">A naïve attempt to represent it as GlobalVariable(or constant) as<o:p></o:p></p>
<p class="MsoNormal">[…]<o:p></o:p></p>
<p class="MsoNormal">!7 = !DIGlobalVariableExpression(var: !8, expr: !DIExpression(DW_OP_consts, 200))<o:p></o:p></p>
<p class="MsoNormal">!8 = distinct !DIGlobalVariable(name: "bar", scope: !2, file: !3, line: 3, type: !9, isLocal: false, isDefinition: true)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">This will materialize in DWARF as:<o:p></o:p></p>
<p class="MsoNormal">0x0000004a: DW_TAG_variable<o:p></o:p></p>
<p class="MsoNormal"> DW_AT_name ("bar")<o:p></o:p></p>
<p class="MsoNormal"> …<o:p></o:p></p>
<p class="MsoNormal"> DW_AT_location (DW_OP_addr 0x2007d4, DW_OP_consts +200) // This is incorrect, pointing to data section<o:p></o:p></p>
<p class="MsoNormal">[…]<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Gfortran is representing this as: **DW_TAG_constant**<br>
0x00000055: **<b>DW_TAG_constant</b>**<o:p></o:p></p>
<p class="MsoNormal"> DW_AT_name ("bar")<o:p></o:p></p>
<p class="MsoNormal"> …<o:p></o:p></p>
<p class="MsoNormal"> DW_AT_type (0x0000006a "const integer(kind=4)")<o:p></o:p></p>
<p class="MsoNormal"> DW_AT_external (true)<o:p></o:p></p>
<p class="MsoNormal"> DW_AT_const_value (0xc8)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Do we have Metadata analog of (DW_TAG_constant) ? I think the primary question here is to how represent this ?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Any inputs appreciated!<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks.. much!<br>
Sourabh.<o:p></o:p></p>
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