<div dir="ltr">On Thu, Aug 22, 2013 at 5:41 PM, David Blaikie <span dir="ltr"><<a href="mailto:dblaikie@gmail.com" target="_blank">dblaikie@gmail.com</a>></span> wrote:<br><div class="gmail_extra"><div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">On Thu, Aug 22, 2013 at 5:34 PM, David Majnemer<br>
<div><div class="h5"><<a href="mailto:david.majnemer@gmail.com">david.majnemer@gmail.com</a>> wrote:<br>
> On Thu, Aug 22, 2013 at 5:14 PM, David Blaikie <<a href="mailto:dblaikie@gmail.com">dblaikie@gmail.com</a>> wrote:<br>
>><br>
>> On Thu, Aug 22, 2013 at 5:08 PM, David Majnemer<br>
>> <<a href="mailto:david.majnemer@gmail.com">david.majnemer@gmail.com</a>> wrote:<br>
>> > On Thu, Aug 22, 2013 at 4:02 PM, David Blaikie <<a href="mailto:dblaikie@gmail.com">dblaikie@gmail.com</a>><br>
>> > wrote:<br>
>> >><br>
>> >><br>
>> >> On Aug 22, 2013 3:02 PM, "David Majnemer" <<a href="mailto:david.majnemer@gmail.com">david.majnemer@gmail.com</a>><br>
>> >> wrote:<br>
>> >> ><br>
>> >> > Hi dblaikie, echristo,<br>
>> >> ><br>
>> >> > We wouldn't emit DW_AT_location for DW_TAG_template_value_parameter<br>
>> >> > if<br>
>> >> > the value the non-type template parameter had was casted. This<br>
>> >> > happens<br>
>> >> > even if there is no textual cast written.<br>
>> >> ><br>
>> >> > <a href="http://llvm-reviews.chandlerc.com/D1478" target="_blank">http://llvm-reviews.chandlerc.com/D1478</a><br>
>> >> ><br>
>> >> > Files:<br>
>> >> > lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp<br>
>> >> > test/DebugInfo/non-type-template-arg-cast.ll<br>
>> >> ><br>
>> >> > Index: lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp<br>
>> >> > ===================================================================<br>
>> >> > --- lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp<br>
>> >> > +++ lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp<br>
>> >> > @@ -1145,6 +1145,7 @@<br>
>> >> > if (!VP.getName().empty())<br>
>> >> > addString(ParamDIE, dwarf::DW_AT_name, VP.getName());<br>
>> >> > if (Value *Val = VP.getValue()) {<br>
>> >> > + Val = Val->stripPointerCasts();<br>
>> >><br>
>> >> Should we strip the casts in the frontend instead? Perhaps there's some<br>
>> >> easy way to get the right/simple thing there?<br>
>> ><br>
>> > If by the "frontend" you mean CGDebugInfo::CollectTemplateParams, then<br>
>> > we<br>
>> > could but I don't know if it would be better. For example, we would need<br>
>> > to<br>
>> > fix this for Expression and Declaration.<br>
>><br>
>> Fair enough, if there are two places that would need to be fixed in<br>
>> the frontend (well, they could presumably be adjusted to fall through<br>
>> to the same stripping code?) I can live with it here. Don't have a<br>
>> strong feeling.<br>
>><br>
>> Do you know why these casts are introduced & whether there are any<br>
>> other things we might see here? (I prefer not to add fixes blindly<br>
>> without understanding why the fix is necessary)<br>
><br>
><br>
> The casts are introduced because of the padding.<br>
> - Y is struct Type but the ABI requires that we have padding at the end of<br>
> the struct. So instead, the object Y is an anonymous LLVM struct type with<br>
> the three padding bytes. The two fields are initialized with zeros and the<br>
> padding is filled with undefs.<br>
> - However, &Y's LLVM type is %struct.Type* and not of type "pointer to<br>
> anonymous struct type".<br>
<br>
</div></div>OK - thanks for the explanation. Yeah, that sort of feels like a<br>
frontend concern & thus a frontend issue to translate this back into a<br>
pointer to struct.Type...<br>
<br>
I'm tossing this up. Might discuss it with you & Eric tomorrow - it's<br>
not important, I'm just indecisive.<br>
<div><div class="h5"><br>
><br>
>><br>
>> >> > if (ConstantInt *CI = dyn_cast<ConstantInt>(Val))<br>
>> >> > addConstantValue(ParamDIE, CI,<br>
>> >> > VP.getType().isUnsignedDIType());<br>
>> >> > else if (GlobalValue *GV = dyn_cast<GlobalValue>(Val)) {<br>
>> >> > Index: test/DebugInfo/non-type-template-arg-cast.ll<br>
>> >> > ===================================================================<br>
>> >> > --- /dev/null<br>
>> >> > +++ test/DebugInfo/non-type-template-arg-cast.ll<br>
>> >> > @@ -0,0 +1,83 @@<br>
>> >> > +; REQUIRES: object-emission<br>
>> >> > +<br>
>> >> > +; RUN: llc -O0 -filetype=obj < %s > %t<br>
>> >> > +; RUN: llvm-dwarfdump %t | FileCheck %s<br>
>> >> > +<br>
>> >> > +; This was created from the following source:<br>
>> >> > +; struct Type {<br>
>> >> > +; unsigned int Data1;<br>
>> >> > +; unsigned short Data2, Data3;<br>
>> >> > +; unsigned char Data4;<br>
>> >> > +; };<br>
>> >><br>
>> >> Is this the simplest class that demonstrates the problem?<br>
>> ><br>
>> > No, I've simplified it a bit.<br>
>> >><br>
>> >> > +; template<const Type *G><br>
>> >> > +; const Type *func() {<br>
>> >> > +; return G;<br>
>> >> > +; }<br>
>> >> > +<br>
>> >> > +; extern const Type Y;<br>
>> >><br>
>> >> Do you need the extern declaration?<br>
>> ><br>
>> > If I don't declare it as extern, I get a warning about using a C++11<br>
>> > extension.<br>
>><br>
>> Which extension would that be?<br>
><br>
><br>
> warning: non-type template argument referring to object 'Y' with internal<br>
> linkage is a C++11 extension [-Wc++11-extensions]<br>
<br>
</div></div>I'm guessing that was because it was 'const. Without the const it<br>
seems to go away.<br>
<br>
Please drop the {} initialization too.<br></blockquote><div><br></div><div>Awkwardly enough, that makes a difference here. The "= {}" notation only initialized the fields to zero and left the padding alone. Not initializing it means that it just gets "zeroinitializer".</div>
<div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div class=""><div class="h5"><span style="color:rgb(34,34,34)"> </span><br></div></div></blockquote><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div class=""><div class="h5">
><br>
>><br>
>><br>
>> > I guess we don't care about it here though. The patch is updated<br>
>> > to reflect this.<br>
>><br>
>> Dropping the const might be nice too - just to keep it simple.<br>
>><br>
>> Type Y;<br>
>> int main() {<br>
>> func<&Y>();<br>
>> }<br>
><br>
><br>
> Will do.<br>
><br>
>><br>
>><br>
>> Also - I think we have an existing test case for non-type template<br>
>> parameters (test/DebugInfo/X86/templates.ll, probably?) - would this<br>
>> be reasonable to add there instead of adding a new test file?<br>
>><br>
>> >><br>
>> >> > +; const Type Y = {};<br>
>> >> > +; int main() {<br>
>> >> > +; func<&Y>();<br>
>> >> > +; }<br>
>> >> > +<br>
>> >> > +; CHECK: DW_TAG_template_value_parameter<br>
>> >> > +; CHECK-NEXT: DW_AT_type<br>
>> >> > +; CHECK-NEXT: DW_AT_name<br>
>> >> > +; CHECK-NEXT: DW_AT_location<br>
>> >> > +; CHECK: NULL<br>
>> >> > +<br>
>> >> > +%struct.Type = type { i32, i16, i16, i8 }<br>
>> >> > +<br>
>> >> > +@Y = constant { i32, i16, i16, i8, [3 x i8] } { i32 0, i16 0, i16 0,<br>
>> >> > i8<br>
>> >> > 0, [3 x i8] undef }, align 4<br>
>> >> > +<br>
>> >> > +; Function Attrs: uwtable<br>
>> >> > +define i32 @main() #0 {<br>
>> >> > +entry:<br>
>> >> > + %call = call %struct.Type* @_Z4funcIXadL_Z1YEEEPK4Typev(), !dbg<br>
>> >> > !28<br>
>> >> > + ret i32 0, !dbg !29<br>
>> >> > +}<br>
>> >> > +<br>
>> >> > +; Function Attrs: nounwind uwtable<br>
>> >> > +define linkonce_odr %struct.Type* @_Z4funcIXadL_Z1YEEEPK4Typev() #1<br>
>> >> > {<br>
>> >> > +entry:<br>
>> >> > + ret %struct.Type* bitcast ({ i32, i16, i16, i8, [3 x i8] }* @Y to<br>
>> >> > %struct.Type*), !dbg !30<br>
>> >> > +}<br>
>> >> > +<br>
>> >> > +attributes #0 = { uwtable "less-precise-fpmad"="false"<br>
>> >> > "no-frame-pointer-elim"="true"<br>
>> >> > "no-frame-pointer-elim-non-leaf"="true"<br>
>> >> > "no-infs-fp-math"="false" "no-nans-fp-math"="false"<br>
>> >> > "stack-protector-buffer-size"="8" "unsafe-fp-math"="false"<br>
>> >> > "use-soft-float"="false" }<br>
>> >> > +attributes #1 = { nounwind uwtable "less-precise-fpmad"="false"<br>
>> >> > "no-frame-pointer-elim"="true"<br>
>> >> > "no-frame-pointer-elim-non-leaf"="true"<br>
>> >> > "no-infs-fp-math"="false" "no-nans-fp-math"="false"<br>
>> >> > "stack-protector-buffer-size"="8" "unsafe-fp-math"="false"<br>
>> >> > "use-soft-float"="false" }<br>
>> >> > +<br>
>> >> > +!<a href="http://llvm.dbg.cu" target="_blank">llvm.dbg.cu</a> = !{!0}<br>
>> >> > +!llvm.module.flags = !{!27}<br>
>> >> > +<br>
>> >> > +!0 = metadata !{i32 786449, metadata !1, i32 4, metadata !"clang<br>
>> >> > version 3.4 ", i1 false, metadata !"", i32 0, metadata !2, metadata<br>
>> >> > !2,<br>
>> >> > metadata !3, metadata !25, metadata !2, metadata !""} ; [<br>
>> >> > DW_TAG_compile_unit ]<br>
>> >> > [/usr/local/google/home/majnemer/llvm/build//var/tmp/dlb.cpp]<br>
>> >> > [DW_LANG_C_plus_plus]<br>
>> >> > +!1 = metadata !{metadata !"/var/tmp/dlb.cpp", metadata<br>
>> >> > !"/usr/local/google/home/majnemer/llvm/build"}<br>
>> >> > +!2 = metadata !{i32 0}<br>
>> >> > +!3 = metadata !{metadata !4, metadata !9}<br>
>> >> > +!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata<br>
>> >> > !"main",<br>
>> >> > metadata !"main", metadata !"", i32 14, metadata !6, i1 false, i1<br>
>> >> > true, i32<br>
>> >> > 0, i32 0, null, i32 256, i1 false, i32 ()* @main, null, null,<br>
>> >> > metadata !2,<br>
>> >> > i32 14} ; [ DW_TAG_subprogram ] [line 14] [def] [main]<br>
>> >> > +!5 = metadata !{i32 786473, metadata !1} ; [<br>
>> >> > DW_TAG_file_type<br>
>> >> > ] [/usr/local/google/home/majnemer/llvm/build//var/tmp/dlb.cpp]<br>
>> >> > +!6 = metadata !{i32 786453, i32 0, i32 0, metadata !"", i32 0, i64<br>
>> >> > 0,<br>
>> >> > i64 0, i64 0, i32 0, null, metadata !7, i32 0, i32 0} ; [<br>
>> >> > DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]<br>
>> >> > +!7 = metadata !{metadata !8}<br>
>> >> > +!8 = metadata !{i32 786468, null, null, metadata !"int", i32 0, i64<br>
>> >> > 32,<br>
>> >> > i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ] [int] [line 0,<br>
>> >> > size 32,<br>
>> >> > align 32, offset 0, enc DW_ATE_signed]<br>
>> >> > +!9 = metadata !{i32 786478, metadata !1, metadata !5, metadata<br>
>> >> > !"func<&Y>", metadata !"func<&Y>", metadata<br>
>> >> > !"_Z4funcIXadL_Z1YEEEPK4Typev",<br>
>> >> > i32 8, metadata !10, i1 false, i1 true, i32 0, i32 0, null, i32 256,<br>
>> >> > i1<br>
>> >> > false, %struct.Type* ()* @_Z4funcIXadL_Z1YEEEPK4Typev, metadata !23,<br>
>> >> > null,<br>
>> >> > metadata !2, i32 8} ; [ DW_TAG_subprogram ] [line 8] [def] [func<&Y>]<br>
>> >> > +!10 = metadata !{i32 786453, i32 0, i32 0, metadata !"", i32 0, i64<br>
>> >> > 0,<br>
>> >> > i64 0, i64 0, i32 0, null, metadata !11, i32 0, i32 0} ; [<br>
>> >> > DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]<br>
>> >> > +!11 = metadata !{metadata !12}<br>
>> >> > +!12 = metadata !{i32 786447, null, null, metadata !"", i32 0, i64<br>
>> >> > 64,<br>
>> >> > i64 64, i64 0, i32 0, metadata !13} ; [ DW_TAG_pointer_type ] [line<br>
>> >> > 0, size<br>
>> >> > 64, align 64, offset 0] [from ]<br>
>> >> > +!13 = metadata !{i32 786470, null, null, metadata !"", i32 0, i64 0,<br>
>> >> > i64 0, i64 0, i32 0, metadata !14} ; [ DW_TAG_const_type ] [line 0,<br>
>> >> > size 0,<br>
>> >> > align 0, offset 0] [from Type]<br>
>> >> > +!14 = metadata !{i32 786451, metadata !1, null, metadata !"Type",<br>
>> >> > i32<br>
>> >> > 1, i64 96, i64 32, i32 0, i32 0, null, metadata !15, i32 0, null,<br>
>> >> > null} ; [<br>
>> >> > DW_TAG_structure_type ] [Type] [line 1, size 96, align 32, offset 0]<br>
>> >> > [def]<br>
>> >> > [from ]<br>
>> >> > +!15 = metadata !{metadata !16, metadata !18, metadata !20, metadata<br>
>> >> > !21}<br>
>> >> > +!16 = metadata !{i32 786445, metadata !1, metadata !14, metadata<br>
>> >> > !"Data1", i32 2, i64 32, i64 32, i64 0, i32 0, metadata !17} ; [<br>
>> >> > DW_TAG_member ] [Data1] [line 2, size 32, align 32, offset 0] [from<br>
>> >> > unsigned<br>
>> >> > int]<br>
>> >> > +!17 = metadata !{i32 786468, null, null, metadata !"unsigned int",<br>
>> >> > i32<br>
>> >> > 0, i64 32, i64 32, i64 0, i32 0, i32 7} ; [ DW_TAG_base_type ]<br>
>> >> > [unsigned<br>
>> >> > int] [line 0, size 32, align 32, offset 0, enc DW_ATE_unsigned]<br>
>> >> > +!18 = metadata !{i32 786445, metadata !1, metadata !14, metadata<br>
>> >> > !"Data2", i32 3, i64 16, i64 16, i64 32, i32 0, metadata !19} ; [<br>
>> >> > DW_TAG_member ] [Data2] [line 3, size 16, align 16, offset 32] [from<br>
>> >> > unsigned short]<br>
>> >> > +!19 = metadata !{i32 786468, null, null, metadata !"unsigned short",<br>
>> >> > i32 0, i64 16, i64 16, i64 0, i32 0, i32 7} ; [ DW_TAG_base_type ]<br>
>> >> > [unsigned<br>
>> >> > short] [line 0, size 16, align 16, offset 0, enc DW_ATE_unsigned]<br>
>> >> > +!20 = metadata !{i32 786445, metadata !1, metadata !14, metadata<br>
>> >> > !"Data3", i32 3, i64 16, i64 16, i64 48, i32 0, metadata !19} ; [<br>
>> >> > DW_TAG_member ] [Data3] [line 3, size 16, align 16, offset 48] [from<br>
>> >> > unsigned short]<br>
>> >> > +!21 = metadata !{i32 786445, metadata !1, metadata !14, metadata<br>
>> >> > !"Data4", i32 4, i64 8, i64 8, i64 64, i32 0, metadata !22} ; [<br>
>> >> > DW_TAG_member ] [Data4] [line 4, size 8, align 8, offset 64] [from<br>
>> >> > unsigned<br>
>> >> > char]<br>
>> >> > +!22 = metadata !{i32 786468, null, null, metadata !"unsigned char",<br>
>> >> > i32<br>
>> >> > 0, i64 8, i64 8, i64 0, i32 0, i32 8} ; [ DW_TAG_base_type ]<br>
>> >> > [unsigned char]<br>
>> >> > [line 0, size 8, align 8, offset 0, enc DW_ATE_unsigned_char]<br>
>> >> > +!23 = metadata !{metadata !24}<br>
>> >> > +!24 = metadata !{i32 786480, null, metadata !"G", metadata !12,<br>
>> >> > %struct.Type* bitcast ({ i32, i16, i16, i8, [3 x i8] }* @Y to<br>
>> >> > %struct.Type*), null, i32 0, i32 0} ; [<br>
>> >> > DW_TAG_template_value_parameter ]<br>
>> >> > +!25 = metadata !{metadata !26}<br>
>> >> > +!26 = metadata !{i32 786484, i32 0, null, metadata !"Y", metadata<br>
>> >> > !"Y",<br>
>> >> > metadata !"", metadata !5, i32 13, metadata !13, i32 0, i32 1, { i32,<br>
>> >> > i16,<br>
>> >> > i16, i8, [3 x i8] }* @Y, null} ; [ DW_TAG_variable ] [Y] [line 13]<br>
>> >> > [def]<br>
>> >> > +!27 = metadata !{i32 2, metadata !"Dwarf Version", i32 3}<br>
>> >> > +!28 = metadata !{i32 15, i32 0, metadata !4, null}<br>
>> >> > +!29 = metadata !{i32 16, i32 0, metadata !4, null}<br>
>> >> > +!30 = metadata !{i32 9, i32 0, metadata !9, null}<br>
>> ><br>
>> ><br>
><br>
><br>
</div></div></blockquote></div><br></div></div>