[MC] Add support for encoding CodeView variable definition ranges

CodeView, like most other debug formats, represents the live range of a
variable so that debuggers might print them out.

They use a variety of records to represent how a particular variable
might be available (in a register, in a frame pointer, etc.) along with
a set of ranges where this debug information is relevant.

However, the format only allows us to use ranges which are limited to a
maximum of 0xF000 in size.  This means that we need to split our debug
information into chunks of 0xF000.

Because the layout of code is not known until *very* late, we must use a
new fragment to record the information we need until we can know
*exactly* what the range is.

llvm-svn: 259868

1 files changed, 14 insertions, 0 deletions

diff --git a/llvm/lib/MC/MCFragment.cpp b/llvm/lib/MC/MCFragment.cpp
index bfadfda..b9889049 100644
--- a/llvm/lib/MC/MCFragment.cpp
+++ b/llvm/lib/MC/MCFragment.cpp
@@ -292,6 +292,9 @@ void MCFragment::destroy() {
     case FT_CVInlineLines:
       delete cast<MCCVInlineLineTableFragment>(this);
       return;
+    case FT_CVDefRange:
+      delete cast<MCCVDefRangeFragment>(this);
+      return;
     case FT_Dummy:
       delete cast<MCDummyFragment>(this);
       return;
@@ -331,6 +334,7 @@ LLVM_DUMP_METHOD void MCFragment::dump() {
   case MCFragment::FT_LEB:   OS << "MCLEBFragment"; break;
   case MCFragment::FT_SafeSEH:    OS << "MCSafeSEHFragment"; break;
   case MCFragment::FT_CVInlineLines: OS << "MCCVInlineLineTableFragment"; break;
+  case MCFragment::FT_CVDefRange: OS << "MCCVDefRangeTableFragment"; break;
   case MCFragment::FT_Dummy: OS << "MCDummyFragment"; break;
   }
 
@@ -435,6 +439,16 @@ LLVM_DUMP_METHOD void MCFragment::dump() {
     OS << " Sym:" << *F->getFnStartSym();
     break;
   }
+  case MCFragment::FT_CVDefRange: {
+    const auto *F = cast<MCCVDefRangeFragment>(this);
+    OS << "\n       ";
+    for (std::pair<const MCSymbol *, const MCSymbol *> RangeStartEnd :
+         F->getRanges()) {
+      OS << " RangeStart:" << RangeStartEnd.first;
+      OS << " RangeEnd:" << RangeStartEnd.second;
+    }
+    break;
+  }
   case MCFragment::FT_Dummy:
     break;
   }