Allow DWARFDebugInfoEntryMinimal::getSubroutineName to resolve cross-unit references.

[friss]

Summary

getSubroutineName is currently only used by llvm-symbolizer, thus add a binary test containing a cross-cu inlining example.

[samsonov]

lib/DebugInfo/DWARFDebugInfoEntry.cpp

31

If the reference is invalid, just return nullptr

test/DebugInfo/Inputs/cross-cu-inlining.c

1

Please provide a better description of how to turn this into an .o file (exact sequence of commands).

[friss]

• Do not assert in findUnitAndExtractFast helper
• Put detailed explanations on how to regenerate the test input binary

[samsonov]

LGTM. Thanks!

lib/DebugInfo/DWARFDebugInfoEntry.cpp

31

Please put parentheses around

Unit && DIE.extractFast(Unit, Offset)

[friss]

Closed by commit rL218245 (authored by @friss).

lib/DebugInfo/DWARFDebugInfoEntry.cpp

 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Dwarf.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 using namespace dwarf;
 typedef DILineInfoSpecifier::FunctionNameKind FunctionNameKind;
 
+// Small helper to extract a DIE pointed by a reference
+// attribute. It looks up the Unit containing the DIE and calls
+// DIE.extractFast with the right unit. Returns new unit on success,
+// nullptr otherwise.
+static const DWARFUnit *findUnitAndExtractFast(DWARFDebugInfoEntryMinimal &DIE,
+                                               const DWARFUnit *Unit,
+                                               uint32_t *Offset) {
+  Unit = Unit->getUnitSection().getUnitForOffset(*Offset);
+  assert(Unit && "Invalid DIE reference provided.");
+  return DIE.extractFast(Unit, Offset) ? Unit : nullptr;
+}
+
 void DWARFDebugInfoEntryMinimal::dump(raw_ostream &OS, const DWARFUnit *u,
                                       unsigned recurseDepth,
                                       unsigned indent) const {
   DataExtractor debug_info_data = u->getDebugInfoExtractor();
   uint32_t offset = Offset;
 
   if (debug_info_data.isValidOffset(offset)) {
     uint32_t abbrCode = debug_info_data.getULEB128(&offset);
DWARFDebugInfoEntryMinimal::getSubroutineName(const DWARFUnit *U,
   }
   if (const char *name = getAttributeValueAsString(U, DW_AT_name, nullptr))
     return name;
   // Try to get name from specification DIE.
   uint32_t spec_ref =
       getAttributeValueAsReference(U, DW_AT_specification, -1U);
   if (spec_ref != -1U) {
     DWARFDebugInfoEntryMinimal spec_die;
-    if (spec_die.extractFast(U, &spec_ref)) {
-      if (const char *name = spec_die.getSubroutineName(U, Kind))
+    if (const DWARFUnit *RefU = findUnitAndExtractFast(spec_die, U, &spec_ref)) {
+      if (const char *name = spec_die.getSubroutineName(RefU, Kind))
         return name;
     }
   }
   // Try to get name from abstract origin DIE.
   uint32_t abs_origin_ref =
       getAttributeValueAsReference(U, DW_AT_abstract_origin, -1U);
   if (abs_origin_ref != -1U) {
     DWARFDebugInfoEntryMinimal abs_origin_die;
-    if (abs_origin_die.extractFast(U, &abs_origin_ref)) {
-      if (const char *name = abs_origin_die.getSubroutineName(U, Kind))
+    if (const DWARFUnit *RefU = findUnitAndExtractFast(abs_origin_die, U,
+                                                       &abs_origin_ref)) {
+      if (const char *name = abs_origin_die.getSubroutineName(RefU, Kind))
         return name;
     }
   }
   return nullptr;
 }
 
 void DWARFDebugInfoEntryMinimal::getCallerFrame(const DWARFUnit *U,
                                                 uint32_t &CallFile,

test/DebugInfo/Inputs/cross-cu-inlining.c

+// a.c -- compile a.c and b.c with lto to generate the binary file
+int i;
+int func(int);
+int main() {
+  return func(i);
+}
+// b.c
+int __attribute__((always_inline)) func(int x) {
+  return x * 2;
+}
+

test/DebugInfo/llvm-symbolizer.test

 RUN: echo "%p/Inputs/macho-universal:i386 0x1f67" >> %t.input
 RUN: echo "%p/Inputs/macho-universal:x86_64 0x100000f05" >> %t.input
 RUN: echo "%p/Inputs/llvm-symbolizer-dwo-test 0x400514" >> %t.input
 RUN: echo "%p/Inputs/fission-ranges.elf-x86_64 0x720" >> %t.input
 RUN: echo "%p/Inputs/arange-overlap.elf-x86_64 0x714" >> %t.input
 RUN: cp %p/Inputs/split-dwarf-test.dwo %T
 RUN: echo "%p/Inputs/split-dwarf-test 0x4004d0" >> %t.input
 RUN: echo "%p/Inputs/split-dwarf-test 0x4004c0" >> %t.input
+RUN: echo "%p/Inputs/cross-cu-inlining.x86_64-macho.o 0x17" >> %t.input
 
 RUN: llvm-symbolizer --functions=linkage --inlining --demangle=false \
 RUN:    --default-arch=i386 < %t.input | FileCheck %s
 
 REQUIRES: shell
 
 CHECK:       main
 CHECK-NEXT: /tmp/dbginfo{{[/\\]}}dwarfdump-test.cc:16

 CHECK: _Z3fooi
 CHECK-NEXT: {{.*}}split-dwarf-test.cc
 CHECK-NEXT: main
 CHECK-NEXT: {{.*}}split-dwarf-test.cc
 
 CHECK: _Z3fooi
 CHECK-NEXT: {{.*}}split-dwarf-test.cc
 
+; func has been inlined into main by LTO. Check that the symbolizer is able
+; to resolve the cross-cu reference and retrieve func's name
+CHECK: func
+CHECK-NEXT: /tmp{{[/\\]}}b.c:2:3
+CHECK-NEXT: main
+CHECK-NEXT: /tmp{{[/\\]}}a.c:4:0
+
 RUN: echo "unexisting-file 0x1234" > %t.input2
 RUN: llvm-symbolizer < %t.input2
 
 RUN: echo "%p/Inputs/macho-universal 0x1f84" > %t.input3
 RUN: llvm-symbolizer < %t.input3 | FileCheck %s --check-prefix=UNKNOWN-ARCH
 
 UNKNOWN-ARCH-NOT: main
 UNKNOWN-ARCH: ??