Add bool to DebugLocDwarfExpression to control emitting comments.

DebugLocDwarfExpression::EmitOp was creating temporary strings by concatenating Twine's.

When emitting to object files, these comments are thrown away.

This commit adds a boolean to the constructor of the DwarfExpression to control whether it will actually emit
any comments.  This prevents it from even generating the temporary comments which would have been thrown away anyway.

llvm-svn: 237827

llvm/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp

@@ -185,7 +185,8 @@ void AsmPrinter::emitSectionOffset(const MCSymbol *Label) const {
 void AsmPrinter::EmitDwarfRegOp(ByteStreamer &Streamer,
                                 const MachineLocation &MLoc) const {
   DebugLocDwarfExpression Expr(*MF->getSubtarget().getRegisterInfo(),
-                               getDwarfDebug()->getDwarfVersion(), Streamer);
+                               getDwarfDebug()->getDwarfVersion(),
+                               OutStreamer->hasRawTextSupport(), Streamer);
   const MCRegisterInfo *MRI = MMI->getContext().getRegisterInfo();
   int Reg = MRI->getDwarfRegNum(MLoc.getReg(), false);
   if (Reg < 0) {

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -108,6 +108,8 @@ static const char *const DWARFGroupName = "DWARF Emission";
 static const char *const DbgTimerName = "DWARF Debug Writer";
 
 void DebugLocDwarfExpression::EmitOp(uint8_t Op, const char *Comment) {
+  if (!PrintComments)
+    return BS.EmitInt8(Op, Twine());
   BS.EmitInt8(
       Op, Comment ? Twine(Comment) + " " + dwarf::OperationEncodingString(Op)
                   : dwarf::OperationEncodingString(Op));
@@ -1477,6 +1479,7 @@ static void emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
                               unsigned PieceOffsetInBits) {
   DebugLocDwarfExpression DwarfExpr(*AP.MF->getSubtarget().getRegisterInfo(),
                                     AP.getDwarfDebug()->getDwarfVersion(),
+                                    AP.OutStreamer->hasRawTextSupport(),
                                     Streamer);
   // Regular entry.
   if (Value.isInt()) {
@@ -1530,6 +1533,7 @@ void DebugLocEntry::finalize(const AsmPrinter &AP, DebugLocStream &Locs,
         // The DWARF spec seriously mandates pieces with no locations for gaps.
         DebugLocDwarfExpression Expr(*AP.MF->getSubtarget().getRegisterInfo(),
                                      AP.getDwarfDebug()->getDwarfVersion(),
+                                     AP.OutStreamer->hasRawTextSupport(),
                                      Streamer);
         Expr.AddOpPiece(PieceOffset-Offset, 0);
         Offset += PieceOffset-Offset;

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h

@@ -34,10 +34,15 @@ protected:
   const TargetRegisterInfo &TRI;
   unsigned DwarfVersion;
 
+  /// \brief Set to true if we want comments to be emitted.  This is usually
+  /// only the case when the AsmPrinter is emitting to a text stream with
+  /// comments enabled.
+  bool PrintComments;
+
 public:
   DwarfExpression(const TargetRegisterInfo &TRI,
-                  unsigned DwarfVersion)
-    : TRI(TRI), DwarfVersion(DwarfVersion) {}
+                  unsigned DwarfVersion, bool PrintComments)
+    : TRI(TRI), DwarfVersion(DwarfVersion), PrintComments(PrintComments) {}
   virtual ~DwarfExpression() {}
 
   /// Output a dwarf operand and an optional assembler comment.
@@ -109,8 +114,9 @@ class DebugLocDwarfExpression : public DwarfExpression {
 
 public:
   DebugLocDwarfExpression(const TargetRegisterInfo &TRI,
-                          unsigned DwarfVersion, ByteStreamer &BS)
-    : DwarfExpression(TRI, DwarfVersion), BS(BS) {}
+                          unsigned DwarfVersion, bool PrintComments,
+                          ByteStreamer &BS)
+    : DwarfExpression(TRI, DwarfVersion, PrintComments), BS(BS) {}
 
   void EmitOp(uint8_t Op, const char *Comment = nullptr) override;
   void EmitSigned(int64_t Value) override;

llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp

@@ -47,7 +47,7 @@ GenerateDwarfTypeUnits("generate-type-units", cl::Hidden,
 DIEDwarfExpression::DIEDwarfExpression(const AsmPrinter &AP, DwarfUnit &DU,
                                        DIELoc &DIE)
     : DwarfExpression(*AP.MF->getSubtarget().getRegisterInfo(),
-                      AP.getDwarfDebug()->getDwarfVersion()),
+                      AP.getDwarfDebug()->getDwarfVersion(), false),
       AP(AP), DU(DU), DIE(DIE) {}
 
 void DIEDwarfExpression::EmitOp(uint8_t Op, const char* Comment) {