Debug info: Emit values in subregisters that do not have a separate

DWARF register number by emitting a super-register + DW_OP_bit_piece.
This is necessary because on x86_64, there are no DWARF register numbers
for i386-style subregisters.
Fixes a bunch of FIXMEs.

rdar://problem/16015314

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201180 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 56 insertions, 4 deletions

diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index bab8aad497..09aedc4cc9 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -868,12 +868,14 @@ void AsmPrinter::EmitDwarfRegOp(const MachineLocation &MLoc,
                                 bool Indirect) const {
   const TargetRegisterInfo *TRI = TM.getRegisterInfo();
   int Reg = TRI->getDwarfRegNum(MLoc.getReg(), false);
+  bool isSubRegister = Reg < 0;
+  unsigned Idx = 0;
 
   for (MCSuperRegIterator SR(MLoc.getReg(), TRI); SR.isValid() && Reg < 0;
        ++SR) {
     Reg = TRI->getDwarfRegNum(*SR, false);
-    // FIXME: Get the bit range this register uses of the superregister
-    // so that we can produce a DW_OP_bit_piece
+    if (Reg >= 0)
+      Idx = TRI->getSubRegIndex(*SR, MLoc.getReg());
   }
 
   // FIXME: Handle cases like a super register being encoded as
@@ -910,7 +912,24 @@ void AsmPrinter::EmitDwarfRegOp(const MachineLocation &MLoc,
     }
   }
 
-  // FIXME: Produce a DW_OP_bit_piece if we used a superregister
+  // Emit Mask
+  if (isSubRegister) {
+    unsigned Size = TRI->getSubRegIdxSize(Idx);
+    unsigned Offset = TRI->getSubRegIdxOffset(Idx);
+    if (Offset > 0) {
+      OutStreamer.AddComment("DW_OP_bit_piece");
+      EmitInt8(dwarf::DW_OP_bit_piece);
+      OutStreamer.AddComment(Twine(Size));
+      EmitULEB128(Size);
+      OutStreamer.AddComment(Twine(Offset));
+      EmitULEB128(Offset);
+    } else {
+      OutStreamer.AddComment("DW_OP_piece");
+      EmitInt8(dwarf::DW_OP_piece);
+      OutStreamer.AddComment(Twine(Size));
+      EmitULEB128(Size);
+    }
+  }
 }
 
 bool AsmPrinter::doFinalization(Module &M) {
diff --git a/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index a1db1e0a2e..6c9e40b066 100644
--- a/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -24,6 +24,7 @@
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Mangler.h"
 #include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/Support/CommandLine.h"
@@ -476,13 +477,45 @@ void DwarfUnit::addVariableAddress(const DbgVariable &DV, DIE *Die,
 /// addRegisterOp - Add register operand.
 void DwarfUnit::addRegisterOp(DIEBlock *TheDie, unsigned Reg) {
   const TargetRegisterInfo *RI = Asm->TM.getRegisterInfo();
-  unsigned DWReg = RI->getDwarfRegNum(Reg, false);
+  int DWReg = RI->getDwarfRegNum(Reg, false);
+  bool isSubRegister = DWReg < 0;
+
+  unsigned Idx = 0;
+
+  // Go up the super-register chain until we hit a valid dwarf register number.
+  for (MCSuperRegIterator SR(Reg, RI); SR.isValid() && DWReg < 0; ++SR) {
+    DWReg = RI->getDwarfRegNum(*SR, false);
+    if (DWReg >= 0)
+      Idx = RI->getSubRegIndex(*SR, Reg);
+  }
+
+  if (DWReg < 0) {
+    DEBUG(llvm::dbgs() << "Invalid Dwarf register number.\n");
+    addUInt(TheDie, dwarf::DW_FORM_data1, dwarf::DW_OP_nop);
+    return;
+  }
+
+  // Emit register
   if (DWReg < 32)
     addUInt(TheDie, dwarf::DW_FORM_data1, dwarf::DW_OP_reg0 + DWReg);
   else {
     addUInt(TheDie, dwarf::DW_FORM_data1, dwarf::DW_OP_regx);
     addUInt(TheDie, dwarf::DW_FORM_udata, DWReg);
   }
+
+  // Emit Mask
+  if (isSubRegister) {
+    unsigned Size = RI->getSubRegIdxSize(Idx);
+    unsigned Offset = RI->getSubRegIdxOffset(Idx);
+    if (Offset > 0) {
+      addUInt(TheDie, dwarf::DW_FORM_data1, dwarf::DW_OP_bit_piece);
+      addUInt(TheDie, dwarf::DW_FORM_data1, Size);
+      addUInt(TheDie, dwarf::DW_FORM_data1, Offset);
+    } else {
+      addUInt(TheDie, dwarf::DW_FORM_data1, dwarf::DW_OP_piece);
+      addUInt(TheDie, dwarf::DW_FORM_data1, Size);
+    }
+  }
 }
 
 /// addRegisterOffset - Add register offset.