[PATCH] D95518: [Debug-Info][XCOFF] support dwarf for XCOFF for assembly output

[Jason Liu via Phabricator via llvm-commits]

jasonliu added inline comments.


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Comment at: llvm/lib/MC/MCAsmStreamer.cpp:2323
+
+  // FIXME: use section end symbol as end of the Section. We need to consider
+  // the explicit sections and -ffunction-sections when we try to generate or
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shchenz wrote:
> jasonliu wrote:
> > I hope this FIXME is not going to stay here for long (and we will quickly have a patch to address this). As this is really a workaround here and it creates different behavior between object file generation and assembly generation which is undesirable.
> I left this as a FIXME because I can not find an easy way to fix this. Why we need this function is because of the difference of the `changeSection` function of `MCAsmStreamer` and `MCObjectStreamer`. `MCObjectStreamer` will change the insert point to the section end, while `MCAsmStreamer` will add a new section start in the assembly output. The `MCAsmStreamer` current behavior is not what we need for debug lines, we can not add another `.text` section when we generate assembly for `.dwline`. 
> So if we want to have the same behavior for `MCAsmStreamer` and `MCObjectStreamer`, we must make sure that we know a function is a section end. So we can add a section end symbol in the function `emitFunctionBodyEnd`. But this seems hard due to explicit sections. When we handle a function in `AsmPrinter` pass, it is hard to know there are other functions(which will be handled later) that also belong to the same section unless a CU level analysis is performed to fetch this info.
I guess one way to do this for assembly would be:
1. collect all the seen text csects somehow into an array.
2. After all the text csects are emitted (doFinalization or emitEndOfAsmFile?), traverse (and switch to) each text csect in the array and emit the section end label for it. 
I think in this way, you could make sure that the section end labels are indeed emitted to the section end.


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Comment at: llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp:2341
+  if (!MAI->usesDwarfFileAndLocDirectives() && MMI->hasDebugInfo())
+    OutStreamer->doFinalizationAtSectionEnd(
+        OutStreamer->getContext().getObjectFileInfo()->getTextSection());
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shchenz wrote:
> jasonliu wrote:
> > I wonder if `doFinalizationAtSectionEnd` really has to be in MCStreamer. At least for this patch, it could just be a helper static function, or private member function of PPCAIXAsmPrinter or even a lambda here, and no other target actually needs it. We could always refactor it to a larger scope later when we find the need for it. 
> I know what you mean, but we must implement this based on `MCStreamer`. We only need this for `MCAsmStreamer` but not for `MCObjectStreamer`. Currently, there is no way to differentiate these two streamers. And we should not differentiate them, as it breaks the abstraction of `MCSreamer`.
You are right. Forgot about the fact that this is for assembly only.


Repository:
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  https://reviews.llvm.org/D95518/new/

https://reviews.llvm.org/D95518