[llvm] r204795 - Follow-up to r204790: don't try to emit line tables if there are no functions with DI in the TU

Tue Apr 1 02:55:53 PDT 2014

2014-04-01 4:07 GMT+04:00 Eric Christopher <echristo at gmail.com>:
> The MI has a DebugLoc and none of the IR do?

Frankly, I'm confused by all this stuff myself :)

Looking at
  test/DebugInfo/COFF/tail-call-without-lexical-scopes.ll
I think the case is that IR *has* !dbg tags, yet
LexicalScopes::empty() actually returned "true" for this MF.

> Otherwise a function is considered a lexical scope for purposes of the
> other check.
>
> -eric
>
> On Wed, Mar 26, 2014 at 1:47 PM, Timur Iskhodzhanov <timurrrr at google.com> wrote:
>> the WinCodeViewLineTables::beginInstruction is called and the MI happens to
>> have a DebugLoc.
>>
>> That's in fact exactly the scenario r204790 has fixed - processing of a
>> function without a lexical scope but with at least one MI having DL.
>>
>> 2014-03-27 0:36 GMT+04:00 Eric Christopher <echristo at gmail.com>:
>>
>>> But how do you know where/etc they are?
>>>
>>> -eric
>>>
>>> On Wed, Mar 26, 2014 at 1:33 PM, Timur Iskhodzhanov <timurrrr at google.com>
>>> wrote:
>>> > 1 file/line number entry for a single jmp instruction.
>>> >
>>> >
>>> > 2014-03-27 0:22 GMT+04:00 Eric Christopher <echristo at gmail.com>:
>>> >
>>> >> On Wed, Mar 26, 2014 at 1:20 PM, Timur Iskhodzhanov
>>> >> <timurrrr at google.com>
>>> >> wrote:
>>> >> >
>>> >> >
>>> >> >
>>> >> > 2014-03-27 0:14 GMT+04:00 Eric Christopher <echristo at gmail.com>:
>>> >> >
>>> >> >> On Wed, Mar 26, 2014 at 1:00 PM, Timur Iskhodzhanov
>>> >> >> <timurrrr at google.com>
>>> >> >> wrote:
>>> >> >> >
>>> >> >> >
>>> >> >> >
>>> >> >> > 2014-03-26 19:24 GMT+04:00 David Blaikie <dblaikie at gmail.com>:
>>> >> >> >
>>> >> >> >> On Wed, Mar 26, 2014 at 4:24 AM, Timur Iskhodzhanov
>>> >> >> >> <timurrrr at google.com>
>>> >> >> >> wrote:
>>> >> >> >> > Author: timurrrr
>>> >> >> >> > Date: Wed Mar 26 06:24:36 2014
>>> >> >> >> > New Revision: 204795
>>> >> >> >> >
>>> >> >> >> > URL: http://llvm.org/viewvc/llvm-project?rev=204795&view=rev
>>> >> >> >> > Log:
>>> >> >> >> > Follow-up to r204790: don't try to emit line tables if there
>>> >> >> >> > are
>>> >> >> >> > no
>>> >> >> >> > functions with DI in the TU
>>> >> >> >>
>>> >> >> >> Hmm - is there any better way to do this? Should we only be
>>> >> >> >> building
>>> >> >> >> line tables for those functions with DI? Then we'd just emit line
>>> >> >> >> tables if we have any (non-empty) line tables to emit, right?
>>> >> >> >
>>> >> >> >
>>> >> >> > Is there a handy function available for that? :)
>>> >> >> >
>>> >> >>
>>> >> >> From DwarfDebug::beginFunction:
>>> >> >>
>>> >> >>   // If there's no debug info for the function we're not going to do
>>> >> >> anything.
>>> >> >>   if (!MMI->hasDebugInfo())
>>> >> >>     return;
>>> >> >>
>>> >> >>   // Grab the lexical scopes for the function, if we don't have any
>>> >> >> of
>>> >> >> those
>>> >> >>   // then we're not going to be able to do anything.
>>> >> >>   LScopes.initialize(*MF);
>>> >> >>   if (LScopes.empty())
>>> >> >>     return;
>>> >> >>
>>> >> >> -eric
>>> >> >
>>> >> >
>>> >> > This is almost exactly the beginning of
>>> >> > WinCodeViewLineTables::beginFunction() as of yesterday :)
>>> >> > So yes, I'm aware of this and I do/did use it.
>>> >> >
>>> >> > However, IIUC it turns out that "if we don't have any [lexical
>>> >> > scopes]
>>> >> > then
>>> >> > we're not going to be able to do anything" we still can emit minimal
>>> >> > DI
>>> >> > for
>>> >> > a function. [see r204790 + r204791]
>>> >>
>>> >> Without looking (my backlog is insane) what's the info you're emitting
>>> >> for
>>> >> it?
>>> >>
>>> >> -eric
>>> >>
>>> >> >
>>> >> >> >> I assume these COFF line tables don't actually get referenced
>>> >> >> >> from
>>> >> >> >> any
>>> >> >> >> other debug info (since the rest of our info is DWARF), but I've
>>> >> >> >> been
>>> >> >> >> thinking of cleaning up our other line table handling code a bit
>>> >> >> >> so
>>> >> >> >> that it's a bit more structured - letting the line table object
>>> >> >> >> itself
>>> >> >> >> decide whether it should be emitted (by virtue of being
>>> >> >> >> non-empty)
>>> >> >> >> and
>>> >> >> >> then having line table clients (CUs in DwarfDebug - no analogy
>>> >> >> >> for
>>> >> >> >> COFF which has no line table client) query the line table to see
>>> >> >> >> if
>>> >> >> >> it'll be there and attach the DW_AT_stmt_list if there will be a
>>> >> >> >> line
>>> >> >> >> table.
>>> >> >> >>
>>> >> >> >> - David
>>> >> >> >>
>>> >> >> >> >
>>> >> >> >> > Added:
>>> >> >> >> >     llvm/trunk/test/DebugInfo/COFF/asan2.ll
>>> >> >> >> > Modified:
>>> >> >> >> >     llvm/trunk/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.cpp
>>> >> >> >> >
>>> >> >> >> > Modified:
>>> >> >> >> > llvm/trunk/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.cpp
>>> >> >> >> > URL:
>>> >> >> >> >
>>> >> >> >> >
>>> >> >> >> >
>>> >> >> >> > http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.cpp?rev=204795&r1=204794&r2=204795&view=diff
>>> >> >> >> >
>>> >> >> >> >
>>> >> >> >> >
>>> >> >> >> >
>>> >> >> >> > ==============================================================================
>>> >> >> >> > --- llvm/trunk/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.cpp
>>> >> >> >> > (original)
>>> >> >> >> > +++ llvm/trunk/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.cpp
>>> >> >> >> > Wed
>>> >> >> >> > Mar
>>> >> >> >> > 26 06:24:36 2014
>>> >> >> >> > @@ -304,11 +304,18 @@ void WinCodeViewLineTables::beginFunctio
>>> >> >> >> >    }
>>> >> >> >> >  }
>>> >> >> >> >
>>> >> >> >> > -void WinCodeViewLineTables::endFunction(const MachineFunction
>>> >> >> >> > *)
>>> >> >> >> > {
>>> >> >> >> > +void WinCodeViewLineTables::endFunction(const MachineFunction
>>> >> >> >> > *MF) {
>>> >> >> >> >    if (!Asm || !CurFn)  // We haven't created any debug info
>>> >> >> >> > for
>>> >> >> >> > this
>>> >> >> >> > function.
>>> >> >> >> >      return;
>>> >> >> >> >
>>> >> >> >> > -  if (!CurFn->Instrs.empty()) {
>>> >> >> >> > +  const Function *GV = MF->getFunction();
>>> >> >> >> > +  assert(FnDebugInfo.count(GV) == true);
>>> >> >> >>
>>> >> >> >> "count == true" seems a bit confusing for a few reasons. Should
>>> >> >> >> that
>>> >> >> >> be either just "assert(x.count(y))" or "assert(x.count(y) != 0)"
>>> >> >> >> (or
>>> >> >> >> greater than zero or 1 or whatever). "== true" always reads as
>>> >> >> >> weird/redundant to me.
>>> >> >> >>
>>> >> >> >> > +  assert(CurFn == &FnDebugInfo[GV]);
>>> >> >> >> > +
>>> >> >> >> > +  if (CurFn->Instrs.empty()) {
>>> >> >> >> > +    FnDebugInfo.erase(GV);
>>> >> >> >> > +    VisitedFunctions.pop_back();
>>> >> >> >> > +  } else {
>>> >> >> >> >      // Define end label for subprogram.
>>> >> >> >> >      MCSymbol *FunctionEndSym =
>>> >> >> >> > Asm->OutStreamer.getContext().CreateTempSymbol();
>>> >> >> >> >      Asm->OutStreamer.EmitLabel(FunctionEndSym);
>>> >> >> >> >
>>> >> >> >> > Added: llvm/trunk/test/DebugInfo/COFF/asan2.ll
>>> >> >> >> > URL:
>>> >> >> >> >
>>> >> >> >> >
>>> >> >> >> >
>>> >> >> >> > http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/COFF/asan2.ll?rev=204795&view=auto
>>> >> >> >> >
>>> >> >> >> >
>>> >> >> >> >
>>> >> >> >> >
>>> >> >> >> > ==============================================================================
>>> >> >> >> > --- llvm/trunk/test/DebugInfo/COFF/asan2.ll (added)
>>> >> >> >> > +++ llvm/trunk/test/DebugInfo/COFF/asan2.ll Wed Mar 26 06:24:36
>>> >> >> >> > 2014
>>> >> >> >> > @@ -0,0 +1,52 @@
>>> >> >> >> > +; RUN: llc -mcpu=core2 -mtriple=i686-pc-win32 -O0 < %s |
>>> >> >> >> > FileCheck
>>> >> >> >> > --check-prefix=X86 %s
>>> >> >> >> > +
>>> >> >> >> > +; This LL file was generated by running clang on the following
>>> >> >> >> > code
>>> >> >> >> > with
>>> >> >> >> > +; -fsanitize=address
>>> >> >> >> > +; D:\asan.c:
>>> >> >> >> > +; 1 unsigned char c = 42;
>>> >> >> >> > +
>>> >> >> >> > +; Just make sure we don't try to emit the line table.
>>> >> >> >> > +; X86-NOT: .section        .debug$S,"rn"
>>> >> >> >> > +
>>> >> >> >> > +; ModuleID = 'asan.c'
>>> >> >> >> > +target datalayout = "e-m:w-p:32:32-i64:64-f80:32-n8:16:32-S32"
>>> >> >> >> > +target triple = "i686-pc-win32"
>>> >> >> >> > +
>>> >> >> >> > + at c = global { i8, [63 x i8] } { i8 42, [63 x i8]
>>> >> >> >> > zeroinitializer
>>> >> >> >> > },
>>> >> >> >> > align 32
>>> >> >> >> > + at llvm.global_ctors = appending global [1 x { i32, void ()* }]
>>> >> >> >> > [{
>>> >> >> >> > i32,
>>> >> >> >> > void ()* } { i32 1, void ()* @asan.module_ctor }]
>>> >> >> >> > + at __asan_gen_ = private constant [7 x i8] c"asan.c\00", align 1
>>> >> >> >> > + at __asan_gen_1 = private unnamed_addr constant [2 x i8]
>>> >> >> >> > c"c\00",
>>> >> >> >> > align 1
>>> >> >> >> > + at 0 = internal global [1 x { i32, i32, i32, i32, i32, i32 }] [{
>>> >> >> >> > i32,
>>> >> >> >> > i32, i32, i32, i32, i32 } { i32 ptrtoint ({ i8, [63 x i8] }* @c
>>> >> >> >> > to
>>> >> >> >> > i32), i32
>>> >> >> >> > 1, i32 64, i32 ptrtoint ([2 x i8]* @__asan_gen_1 to i32), i32
>>> >> >> >> > ptrtoint ([7 x
>>> >> >> >> > i8]* @__asan_gen_ to i32), i32 0 }]
>>> >> >> >> > + at llvm.global_dtors = appending global [1 x { i32, void ()* }]
>>> >> >> >> > [{
>>> >> >> >> > i32,
>>> >> >> >> > void ()* } { i32 1, void ()* @asan.module_dtor }]
>>> >> >> >> > +
>>> >> >> >> > +define internal void @asan.module_ctor() {
>>> >> >> >> > +  call void @__asan_init_v3()
>>> >> >> >> > +  call void @__asan_register_globals(i32 ptrtoint ([1 x { i32,
>>> >> >> >> > i32,
>>> >> >> >> > i32, i32, i32, i32 }]* @0 to i32), i32 1)
>>> >> >> >> > +  ret void
>>> >> >> >> > +}
>>> >> >> >> > +
>>> >> >> >> > +declare void @__asan_init_v3()
>>> >> >> >> > +
>>> >> >> >> > +declare void @__asan_before_dynamic_init(i32)
>>> >> >> >> > +
>>> >> >> >> > +declare void @__asan_after_dynamic_init()
>>> >> >> >> > +
>>> >> >> >> > +declare void @__asan_register_globals(i32, i32)
>>> >> >> >> > +
>>> >> >> >> > +declare void @__asan_unregister_globals(i32, i32)
>>> >> >> >> > +
>>> >> >> >> > +define internal void @asan.module_dtor() {
>>> >> >> >> > +  call void @__asan_unregister_globals(i32 ptrtoint ([1 x {
>>> >> >> >> > i32,
>>> >> >> >> > i32,
>>> >> >> >> > i32, i32, i32, i32 }]* @0 to i32), i32 1)
>>> >> >> >> > +  ret void
>>> >> >> >> > +}
>>> >> >> >> > +
>>> >> >> >> > +!llvm.dbg.cu = !{!0}
>>> >> >> >> > +!llvm.module.flags = !{!3, !4}
>>> >> >> >> > +!llvm.ident = !{!5}
>>> >> >> >> > +
>>> >> >> >> > +!0 = metadata !{i32 786449, metadata !1, i32 12, metadata
>>> >> >> >> > !"clang
>>> >> >> >> > version 3.5.0 ", i1 false, metadata !"", i32 0, metadata !2,
>>> >> >> >> > metadata
>>> >> >> >> > !2,
>>> >> >> >> > metadata !2, metadata !2, metadata !2, metadata !"", i32 2} ; [
>>> >> >> >> > DW_TAG_compile_unit ] [D:\/asan.c] [DW_LANG_C99]
>>> >> >> >> > +!1 = metadata !{metadata !"asan.c", metadata !"D:\5C"}
>>> >> >> >> > +!2 = metadata !{}
>>> >> >> >> > +!3 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
>>> >> >> >> > +!4 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
>>> >> >> >> > +!5 = metadata !{metadata !"clang version 3.5.0 "}
>>> >> >> >> >
>>> >> >> >> >
>>> >> >> >> > _______________________________________________
>>> >> >> >> > llvm-commits mailing list
>>> >> >> >> > llvm-commits at cs.uiuc.edu
>>> >> >> >> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>> >> >> >
>>> >> >> >
>>> >> >> >
>>> >> >> > _______________________________________________
>>> >> >> > llvm-commits mailing list
>>> >> >> > llvm-commits at cs.uiuc.edu
>>> >> >> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>> >> >> >
>>> >> >
>>> >> >
>>> >
>>> >
>>
>>