Cleanup: Calls to getDwarfRegNum() may actually fail, if there is

no DWARF register number mapping, or if the register was a virtual
register that was never materialized. Previously, we would just emit a
bogus location, after this patch we don't emit a location at all by
doing an early exit.

After my bugfix in r223401 today, this doesn't actually happen on any
target that I tested this with, but it's still preferable to make the
possibility of a failure explicit.

llvm-svn: 223428

3 files changed, 44 insertions, 27 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 38100bc2f4c..6901d2290e2 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -746,14 +746,17 @@ void DwarfCompileUnit::addAddress(DIE &Die, dwarf::Attribute Attribute,
                                   bool Indirect) {
   DIELoc *Loc = new (DIEValueAllocator) DIELoc();
 
+  bool validReg;
   if (Location.isReg() && !Indirect)
-    addRegisterOpPiece(*Loc, Location.getReg());
-  else {
-    addRegisterOffset(*Loc, Location.getReg(), Location.getOffset());
-    if (Indirect && !Location.isReg()) {
-      addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_deref);
-    }
-  }
+    validReg = addRegisterOpPiece(*Loc, Location.getReg());
+  else
+    validReg = addRegisterOffset(*Loc, Location.getReg(), Location.getOffset());
+
+  if (!validReg)
+    return;
+
+  if (!Location.isReg() && Indirect)
+    addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_deref);
 
   // Now attach the location information to the DIE.
   addBlock(Die, Attribute, Loc);
@@ -769,25 +772,29 @@ void DwarfCompileUnit::addComplexAddress(const DbgVariable &DV, DIE &Die,
   DIELoc *Loc = new (DIEValueAllocator) DIELoc();
   unsigned N = DV.getNumAddrElements();
   unsigned i = 0;
+  bool validReg;
   if (Location.isReg()) {
     if (N >= 2 && DV.getAddrElement(0) == dwarf::DW_OP_plus) {
       assert(!DV.getVariable().isIndirect() &&
              "double indirection not handled");
       // If first address element is OpPlus then emit
       // DW_OP_breg + Offset instead of DW_OP_reg + Offset.
-      addRegisterOffset(*Loc, Location.getReg(), DV.getAddrElement(1));
+      validReg = addRegisterOffset(*Loc, Location.getReg(), DV.getAddrElement(1));
       i = 2;
     } else if (N >= 2 && DV.getAddrElement(0) == dwarf::DW_OP_deref) {
       assert(!DV.getVariable().isIndirect() &&
              "double indirection not handled");
-      addRegisterOpPiece(*Loc, Location.getReg(),
-                         DV.getExpression().getPieceSize(),
-                         DV.getExpression().getPieceOffset());
+      validReg = addRegisterOpPiece(*Loc, Location.getReg(),
+                                 DV.getExpression().getPieceSize(),
+                                 DV.getExpression().getPieceOffset());
       i = 3;
     } else
-      addRegisterOpPiece(*Loc, Location.getReg());
+      validReg = addRegisterOpPiece(*Loc, Location.getReg());
   } else
-    addRegisterOffset(*Loc, Location.getReg(), Location.getOffset());
+    validReg = addRegisterOffset(*Loc, Location.getReg(), Location.getOffset());
+
+  if (!validReg)
+    return;
 
   for (; i < N; ++i) {
     uint64_t Element = DV.getAddrElement(i);
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 919d9d27480..9394eaff0c9 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -401,7 +401,7 @@ void DwarfUnit::addSourceLine(DIE &Die, DINameSpace NS) {
 /// addRegisterOp - Add register operand.
 // FIXME: Ideally, this would share the implementation with
 // AsmPrinter::EmitDwarfRegOpPiece.
-void DwarfUnit::addRegisterOpPiece(DIELoc &TheDie, unsigned Reg,
+bool DwarfUnit::addRegisterOpPiece(DIELoc &TheDie, unsigned Reg,
                                    unsigned SizeInBits, unsigned OffsetInBits) {
   const TargetRegisterInfo *RI = Asm->TM.getSubtargetImpl()->getRegisterInfo();
   int DWReg = RI->getDwarfRegNum(Reg, false);
@@ -416,11 +416,8 @@ void DwarfUnit::addRegisterOpPiece(DIELoc &TheDie, unsigned Reg,
       Idx = RI->getSubRegIndex(*SR, Reg);
   }
 
-  if (DWReg < 0) {
-    DEBUG(dbgs() << "Invalid Dwarf register number.\n");
-    addUInt(TheDie, dwarf::DW_FORM_data1, dwarf::DW_OP_nop);
-    return;
-  }
+  if (DWReg < 0)
+    return false;
 
   // Emit register.
   if (DWReg < 32)
@@ -460,13 +457,17 @@ void DwarfUnit::addRegisterOpPiece(DIELoc &TheDie, unsigned Reg,
       addUInt(TheDie, dwarf::DW_FORM_data1, PieceSizeInBits/SizeOfByte);
     }
   }
+  return true;
 }
 
 /// addRegisterOffset - Add register offset.
-void DwarfUnit::addRegisterOffset(DIELoc &TheDie, unsigned Reg,
+bool DwarfUnit::addRegisterOffset(DIELoc &TheDie, unsigned Reg,
                                   int64_t Offset) {
   const TargetRegisterInfo *RI = Asm->TM.getSubtargetImpl()->getRegisterInfo();
-  unsigned DWReg = RI->getDwarfRegNum(Reg, false);
+  int DWReg = RI->getDwarfRegNum(Reg, false);
+  if (DWReg < 0)
+    return false;
+
   const TargetRegisterInfo *TRI = Asm->TM.getSubtargetImpl()->getRegisterInfo();
   if (Reg == TRI->getFrameRegister(*Asm->MF))
     // If variable offset is based in frame register then use fbreg.
@@ -478,6 +479,7 @@ void DwarfUnit::addRegisterOffset(DIELoc &TheDie, unsigned Reg,
     addUInt(TheDie, dwarf::DW_FORM_udata, DWReg);
   }
   addSInt(TheDie, dwarf::DW_FORM_sdata, Offset);
+  return true;
 }
 
 /* Byref variables, in Blocks, are declared by the programmer as "SomeType
@@ -581,10 +583,14 @@ void DwarfUnit::addBlockByrefAddress(const DbgVariable &DV, DIE &Die,
   // variable's location.
   DIELoc *Loc = new (DIEValueAllocator) DIELoc();
 
+  bool validReg;
   if (Location.isReg())
-    addRegisterOpPiece(*Loc, Location.getReg());
+    validReg = addRegisterOpPiece(*Loc, Location.getReg());
   else
-    addRegisterOffset(*Loc, Location.getReg(), Location.getOffset());
+    validReg = addRegisterOffset(*Loc, Location.getReg(), Location.getOffset());
+
+  if (!validReg)
+    return;
 
   // If we started with a pointer to the __Block_byref... struct, then
   // the first thing we need to do is dereference the pointer (DW_OP_deref).
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
index f40c937a632..80b2abcf641 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
@@ -253,12 +253,16 @@ public:
   /// addTemplateParams - Add template parameters in buffer.
   void addTemplateParams(DIE &Buffer, DIArray TParams);
 
-  /// addRegisterOp - Add register operand.
-  void addRegisterOpPiece(DIELoc &TheDie, unsigned Reg,
+  /// \brief Add register operand.
+  /// \returns false if the register does not exist, e.g., because it was never
+  /// materialized.
+  bool addRegisterOpPiece(DIELoc &TheDie, unsigned Reg,
                           unsigned SizeInBits = 0, unsigned OffsetInBits = 0);
 
-  /// addRegisterOffset - Add register offset.
-  void addRegisterOffset(DIELoc &TheDie, unsigned Reg, int64_t Offset);
+  /// \brief Add register offset.
+  /// \returns false if the register does not exist, e.g., because it was never
+  /// materialized.
+  bool addRegisterOffset(DIELoc &TheDie, unsigned Reg, int64_t Offset);
 
   // FIXME: Should be reformulated in terms of addComplexAddress.
   /// addBlockByrefAddress - Start with the address based on the location