[llvm] r200422 - Turn on CU ranges if we've got multiple compile units in the same

[Eric Christopher]

On Wed, Jan 29, 2014 at 2:37 PM, Eric Christopher <echristo at gmail.com> wrote:
> On Wed, Jan 29, 2014 at 2:32 PM, David Blaikie <dblaikie at gmail.com> wrote:
>>
>>
>>
>> On Wed, Jan 29, 2014 at 2:26 PM, Eric Christopher <echristo at gmail.com>
>> wrote:
>>>
>>> On Wed, Jan 29, 2014 at 2:23 PM, David Blaikie <dblaikie at gmail.com> wrote:
>>> >
>>> >
>>> >
>>> > On Wed, Jan 29, 2014 at 2:06 PM, Eric Christopher <echristo at gmail.com>
>>> > wrote:
>>> >>
>>> >> Author: echristo
>>> >> Date: Wed Jan 29 16:06:27 2014
>>> >> New Revision: 200422
>>> >>
>>> >> URL: http://llvm.org/viewvc/llvm-project?rev=200422&view=rev
>>> >> Log:
>>> >> Turn on CU ranges if we've got multiple compile units in the same
>>> >> module since there's no range guarantee that we could make given
>>> >> output order. This also fixes up the testcases that have multiple
>>> >> CUs to have the correct range offset.
>>> >
>>> >
>>> > What if LTO together a debug and non-debug module together? We'll still
>>> > have
>>> > one CU, but we'll have functions that aren't in that CU - and
>>> > incorrectly
>>> > describe that using an "all text" range?
>>> >
>>>
>>> ... Short of saying "always use DW_AT_ranges" I don't have a good
>>> solution for this. I'm somewhat down with that, but...
>>
>>
>> Perhaps you were addressing this with the "there's no range guarantee that
>> we could make given output order" (I'm not /quite/ sure how to parse that
>> sentence) - but I thought we'd settled on the idea that we could rely on
>> output order and just coalesce functions/ranges that came one after the
>> other. Or did you come up with some cases that breaks down for/that we care
>> about?
>>
>
> If you have functions that aren't associated with a particular CU
> there's no way of knowing which functions those are. We can only rely
> on the output order to determine whether or not a function is not
> going to appear in debug info output. At least not at the moment. I
> imagine if we were to do so we'd run into the assert at
> DwarfDebug.cpp:1583 right now if we even tried linking the two modules
> together. :\

FWIW we don't seem to. Wacky.

Anyhow, continuing down the unified range path.

-eric

>
>> That way we'd still get high/low whenever it's contiguous, and otherwise
>> we'd use ranges.
>>
>
> Still don't have this way of doing it in yet, but that's an idea yes.
> I'll see how it works in practice.
>
> -eric
>
>>>
>>>
>>> -eric
>>>
>>> >>
>>> >>
>>> >> Modified:
>>> >>     llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>>> >>     llvm/trunk/test/DebugInfo/X86/stmt-list-multiple-compile-units.ll
>>> >>
>>> >> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>>> >> URL:
>>> >>
>>> >> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=200422&r1=200421&r2=200422&view=diff
>>> >>
>>> >>
>>> >> ==============================================================================
>>> >> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
>>> >> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Wed Jan 29
>>> >> 16:06:27
>>> >> 2014
>>> >> @@ -1119,10 +1119,12 @@ void DwarfDebug::endSections() {
>>> >>    }
>>> >>
>>> >>    // For now only turn on CU ranges if we've explicitly asked for it,
>>> >> -  // we have -ffunction-sections enabled, or we've emitted a function
>>> >> -  // into a unique section. At this point all sections should be
>>> >> finalized
>>> >> -  // except for dwarf sections.
>>> >> -  HasCURanges = DwarfCURanges || UsedNonDefaultText ||
>>> >> +  // we have -ffunction-sections enabled, we've emitted a function
>>> >> +  // into a unique section, or we're using LTO. If we're using LTO
>>> >> then
>>> >> +  // we can't know that any particular function in the module is
>>> >> correlated
>>> >> +  // to a particular CU and so we need to be conservative. At this
>>> >> point
>>> >> all
>>> >> +  // sections should be finalized except for dwarf sections.
>>> >> +  HasCURanges = DwarfCURanges || UsedNonDefaultText || (CUMap.size() >
>>> >> 1)
>>> >> ||
>>> >>                  TargetMachine::getFunctionSections();
>>> >>  }
>>> >>
>>> >>
>>> >> Modified:
>>> >> llvm/trunk/test/DebugInfo/X86/stmt-list-multiple-compile-units.ll
>>> >> URL:
>>> >>
>>> >> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/stmt-list-multiple-compile-units.ll?rev=200422&r1=200421&r2=200422&view=diff
>>> >>
>>> >>
>>> >> ==============================================================================
>>> >> --- llvm/trunk/test/DebugInfo/X86/stmt-list-multiple-compile-units.ll
>>> >> (original)
>>> >> +++ llvm/trunk/test/DebugInfo/X86/stmt-list-multiple-compile-units.ll
>>> >> Wed
>>> >> Jan 29 16:06:27 2014
>>> >> @@ -8,11 +8,11 @@
>>> >>  ; CHECK: .debug_info contents:
>>> >>  ; CHECK: DW_TAG_compile_unit
>>> >>  ; CHECK: DW_AT_stmt_list [DW_FORM_sec_offset]   (0x00000000)
>>> >> -; CHECK: DW_AT_low_pc [DW_FORM_addr]       (0x0000000000000000)
>>> >> +; CHECK: DW_AT_ranges [DW_FORM_sec_offset]      (0x00000000)
>>> >>
>>> >>  ; CHECK: DW_TAG_compile_unit
>>> >>  ; CHECK: DW_AT_stmt_list [DW_FORM_sec_offset]   (0x0000003c)
>>> >> -; CHECK: DW_AT_low_pc [DW_FORM_addr]       (0x0000000000000000)
>>> >> +; CHECK: DW_AT_ranges [DW_FORM_sec_offset]      (0x00000020)
>>> >>
>>> >>  ; CHECK: .debug_line contents:
>>> >>  ; CHECK-NEXT: Line table prologue:
>>> >> @@ -25,12 +25,12 @@
>>> >>
>>> >>  ; DWARF3: .debug_info contents:
>>> >>  ; DWARF3: DW_TAG_compile_unit
>>> >> -; DWARF3: DW_AT_stmt_list [DW_FORM_data4]   (0x00000000)
>>> >> -; DWARF3: DW_AT_low_pc [DW_FORM_addr]       (0x0000000000000000)
>>> >> +; DWARF3: DW_AT_stmt_list [DW_FORM_data4]    (0x00000000)
>>> >> +; DWARF3: DW_AT_ranges [DW_FORM_data4]       (0x00000000)
>>> >>
>>> >>  ; DWARF3: DW_TAG_compile_unit
>>> >>  ; DWARF3: DW_AT_stmt_list [DW_FORM_data4]   (0x0000003c)
>>> >> -; DWARF3: DW_AT_low_pc [DW_FORM_addr]       (0x0000000000000000)
>>> >> +; DWARF3: DW_AT_ranges [DW_FORM_data4]      (0x00000020)
>>> >>
>>> >>  ; DWARF3: .debug_line contents:
>>> >>  ; DWARF3-NEXT: Line table prologue:
>>> >>
>>> >>
>>> >> _______________________________________________
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>>> >> llvm-commits at cs.uiuc.edu
>>> >> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>> >
>>> >
>>
>>