[PATCH] D25434: Generate more debug info in -gmlt

[Dehao Chen via llvm-commits]

danielcdh created this revision.
danielcdh added reviewers: dblaikie, echristo, davidxl.
danielcdh added a subscriber: llvm-commits.
Herald added a subscriber: mehdi_amini.

SamplePGO binaries built with -gmlt to collect profile. The current -gmlt debug info is limited, and we need some additional info:

- start line of all subprograms
- linkage name of all subprograms
- standalone subprograms (functions that has neither inlined nor been inlined)

This patch adds these information to the -gmlt binary. The impact on speccpu2006 binary size (size increase comparing with -g0 binary, also includes data for -g binary, which does not change with this patch):

  -gmlt(orig) -gmlt(patched) -g

433.milc       4.68%       5.40%          19.73%
444.namd       8.45%       8.93%          45.99%
447.dealII     97.43%      115.21%        374.89%
450.soplex     27.75%      31.88%         126.04%
453.povray     21.81%      26.16%         92.03%
470.lbm        0.60%       0.67%          1.96%
482.sphinx3    5.77%       6.47%          26.17%
400.perlbench  17.81%      19.43%         73.08%
401.bzip2      3.73%       3.92%          12.18%
403.gcc        31.75%      34.48%         122.75%
429.mcf        0.78%       0.88%          3.89%
445.gobmk      6.08%       7.92%          42.27%
456.hmmer      10.36%      11.25%         35.23%
458.sjeng      5.08%       5.42%          14.36%
462.libquantum 1.71%       1.96%          6.36%
464.h264ref    15.61%      16.56%         43.92%
471.omnetpp    11.93%      15.84%         60.09%
473.astar      3.11%       3.69%          14.18%
483.xalancbmk  56.29%      81.63%         353.22%
geomean        15.60%      18.30%         57.81%

Debug info size change for -gmlt binary with this patch:

433.milc       13.46%
444.namd       5.35%
447.dealII     18.21%
450.soplex     14.68%
453.povray     19.65%
470.lbm        6.03%
482.sphinx3    11.21%
400.perlbench  8.91%
401.bzip2      4.41%
403.gcc        8.56%
429.mcf        8.24%
445.gobmk      29.47%
456.hmmer      8.19%
458.sjeng      6.05%
462.libquantum 11.23%
464.h264ref    5.93%
471.omnetpp    31.89%
473.astar      16.20%
483.xalancbmk  44.62%
geomean        16.83%


https://reviews.llvm.org/D25434

Files:
  lib/CodeGen/AsmPrinter/DwarfDebug.cpp
  lib/CodeGen/AsmPrinter/DwarfUnit.cpp


Index: lib/CodeGen/AsmPrinter/DwarfUnit.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -1176,20 +1176,19 @@
 
 void DwarfUnit::applySubprogramAttributes(const DISubprogram *SP, DIE &SPDie,
                                           bool Minimal) {
-  if (!Minimal)
-    if (applySubprogramDefinitionAttributes(SP, SPDie))
-      return;
+  if (applySubprogramDefinitionAttributes(SP, SPDie))
+    return;
 
   // Constructors and operators for anonymous aggregates do not have names.
   if (!SP->getName().empty())
     addString(SPDie, dwarf::DW_AT_name, SP->getName());
 
+  addSourceLine(SPDie, SP);
+
   // Skip the rest of the attributes under -gmlt to save space.
   if (Minimal)
     return;
 
-  addSourceLine(SPDie, SP);
-
   // Add the prototype if we have a prototype and we have a C like
   // language.
   uint16_t Language = getLanguage();
Index: lib/CodeGen/AsmPrinter/DwarfDebug.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1128,21 +1128,6 @@
   // Add the range of this function to the list of ranges for the CU.
   TheCU.addRange(RangeSpan(Asm->getFunctionBegin(), Asm->getFunctionEnd()));
 
-  // Under -gmlt, skip building the subprogram if there are no inlined
-  // subroutines inside it.
-  if (TheCU.getCUNode()->getEmissionKind() == DICompileUnit::LineTablesOnly &&
-      LScopes.getAbstractScopesList().empty() && !IsDarwin) {
-    assert(InfoHolder.getScopeVariables().empty());
-    assert(DbgValues.empty());
-    // FIXME: This wouldn't be true in LTO with a -g (with inlining) CU followed
-    // by a -gmlt CU. Add a test and remove this assertion.
-    assert(AbstractVariables.empty());
-    PrevLabel = nullptr;
-    CurFn = nullptr;
-    DebugHandlerBase::endFunction(MF);
-    return;
-  }
-
 #ifndef NDEBUG
   size_t NumAbstractScopes = LScopes.getAbstractScopesList().size();
 #endif


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