Debug info: Infrastructure to support debug locations for fragmented

variables (for example, by-value struct arguments passed in registers, or
large integer values split across several smaller registers).
On the IR level, this adds a new type of complex address operation OpPiece
to DIVariable that describes size and offset of a variable fragment.
On the DWARF emitter level, all pieces describing the same variable are
collected, sorted and emitted as DWARF expressions using the DW_OP_piece
and DW_OP_bit_piece operators.

http://reviews.llvm.org/D3373
rdar://problem/15928306

What this patch doesn't do / Future work:
- This patch only adds the backend machinery to make this work, patches
  that change SROA and SelectionDAG's type legalizer to actually create
  such debug info will follow. (http://reviews.llvm.org/D2680)
- Making the DIVariable complex expressions into an argument of dbg.value
  will reduce the memory footprint of the debug metadata.
- The sorting/uniquing of pieces should be moved into DebugLocEntry,
  to facilitate the merging of multi-piece entries.

llvm-svn: 214576

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 7cbad1ec4a9..51c6c952ea6 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -618,7 +618,11 @@ static bool emitDebugValueComment(const MachineInstr *MI, AsmPrinter &AP) {
     if (!Name.empty())
       OS << Name << ":";
   }
-  OS << V.getName() << " <- ";
+  OS << V.getName();
+  if (V.isVariablePiece())
+    OS << " [piece offset=" << V.getPieceOffset()
+       << " size="<<V.getPieceSize()<<"]";
+  OS << " <- ";
 
   // The second operand is only an offset if it's an immediate.
   bool Deref = MI->getOperand(0).isReg() && MI->getOperand(1).isImm();