[DWARF] - Make collectAddressRanges() return section index in addition to Low/High PC

This change is intended to use for LLD in D33183. 
Problem we have in LLD when building .gdb_index is that we need to know section 
which address range belongs to.

Previously it was solved on LLD side by providing fake section addresses
with use of llvm::LoadedObjectInfo interface. We assigned file offsets as addressed.
Then after obtaining ranges lists, for each range we had to find section ID's.
That not only was slow, but also complicated implementation and was the reason 
of incorrect behavior when
sections share the same offsets, like D33176 shows.

This patch makes DWARF parsers to return section index as well. 
That solves problem mentioned above.

Differential revision: https://reviews.llvm.org/D33184

llvm-svn: 303978

1 files changed, 8 insertions, 5 deletions

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
index e3bd759ba94..fd45c77d374 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
@@ -211,13 +211,16 @@ Optional<uint64_t> DWARFDie::getHighPC(uint64_t LowPC) const {
   return None;
 }
 
-bool DWARFDie::getLowAndHighPC(uint64_t &LowPC, uint64_t &HighPC) const {
-  auto LowPcAddr = toAddress(find(DW_AT_low_pc));
+bool DWARFDie::getLowAndHighPC(uint64_t &LowPC, uint64_t &HighPC,
+                               uint64_t &SectionIndex) const {
+  auto F = find(DW_AT_low_pc);
+  auto LowPcAddr = toAddress(F);
   if (!LowPcAddr)
     return false;
   if (auto HighPcAddr = getHighPC(*LowPcAddr)) {
     LowPC = *LowPcAddr;
     HighPC = *HighPcAddr;
+    SectionIndex = F->getSectionIndex();
     return true;
   }
   return false;
@@ -228,9 +231,9 @@ DWARFDie::getAddressRanges() const {
   if (isNULL())
     return DWARFAddressRangesVector();
   // Single range specified by low/high PC.
-  uint64_t LowPC, HighPC;
-  if (getLowAndHighPC(LowPC, HighPC))
-    return {{LowPC, HighPC}};
+  uint64_t LowPC, HighPC, Index;
+  if (getLowAndHighPC(LowPC, HighPC, Index))
+    return {{LowPC, HighPC, Index}};
 
   // Multiple ranges from .debug_ranges section.
   auto RangesOffset = toSectionOffset(find(DW_AT_ranges));