[DEBUGINFO, NVPTX] Try to pack bytes data into a single string.

Summary:
If the target does not support `.asciz` and `.ascii` directives, the
strings are represented as bytes and each byte is placed on the new line
as a separate byte directive `.b8 <data>`. NVPTX target allows to
represent the vector of the data of the same type as a vector, where
values are separated using `,` symbol: `.b8 <data1>,<data2>,...`. This
allows to reduce the size of the final PTX file. Ptxas tool includes ptx
files into the resulting binary object, so reducing the size of the PTX
file is important.

Reviewers: tra, jlebar, echristo

Subscribers: jholewinski, llvm-commits

Differential Revision: https://reviews.llvm.org/D45822

llvm-svn: 345142

5 files changed, 52 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DIE.cpp b/llvm/lib/CodeGen/AsmPrinter/DIE.cpp
index ca3a750..301fd9e 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DIE.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DIE.cpp
@@ -589,8 +589,7 @@ void DIEString::print(raw_ostream &O) const {
 //===----------------------------------------------------------------------===//
 void DIEInlineString::EmitValue(const AsmPrinter *AP, dwarf::Form Form) const {
   if (Form == dwarf::DW_FORM_string) {
-    for (char ch : S)
-      AP->emitInt8(ch);
+    AP->OutStreamer->EmitBytes(S);
     AP->emitInt8(0);
     return;
   }
diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
index c4744ac..f75a8e0 100644
--- a/llvm/lib/MC/MCAsmStreamer.cpp
+++ b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -858,10 +858,14 @@ void MCAsmStreamer::EmitBytes(StringRef Data) {
   // supported, emit as vector of 8bits data.
   if (Data.size() == 1 ||
       !(MAI->getAscizDirective() || MAI->getAsciiDirective())) {
-    const char *Directive = MAI->getData8bitsDirective();
-    for (const unsigned char C : Data.bytes()) {
-      OS << Directive << (unsigned)C;
-      EmitEOL();
+    if (MCTargetStreamer *TS = getTargetStreamer()) {
+      TS->emitRawBytes(Data);
+    } else {
+      const char *Directive = MAI->getData8bitsDirective();
+      for (const unsigned char C : Data.bytes()) {
+        OS << Directive << (unsigned)C;
+        EmitEOL();
+      }
     }
     return;
   }
diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index bfcf6d47..1b704b8 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -72,6 +72,18 @@ void MCTargetStreamer::emitValue(const MCExpr *Value) {
   Streamer.EmitRawText(OS.str());
 }
 
+void MCTargetStreamer::emitRawBytes(StringRef Data) {
+  const MCAsmInfo *MAI = Streamer.getContext().getAsmInfo();
+  const char *Directive = MAI->getData8bitsDirective();
+  for (const unsigned char C : Data.bytes()) {
+    SmallString<128> Str;
+    raw_svector_ostream OS(Str);
+
+    OS << Directive << (unsigned)C;
+    Streamer.EmitRawText(OS.str());
+  }
+}
+
 void MCTargetStreamer::emitAssignment(MCSymbol *Symbol, const MCExpr *Value) {}
 
 MCStreamer::MCStreamer(MCContext &Ctx)
diff --git a/llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXTargetStreamer.cpp b/llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXTargetStreamer.cpp
index aeb90ec..71ca7a5 100644
--- a/llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXTargetStreamer.cpp
+++ b/llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXTargetStreamer.cpp
@@ -92,3 +92,30 @@ void NVPTXTargetStreamer::changeSection(const MCSection *CurSection,
     OS << "//\t{\n";
   }
 }
+
+void NVPTXTargetStreamer::emitRawBytes(StringRef Data) {
+  const MCAsmInfo *MAI = Streamer.getContext().getAsmInfo();
+  const char *Directive = MAI->getData8bitsDirective();
+  unsigned NumElements = Data.size();
+  const unsigned MaxLen = 40;
+  unsigned NumChunks = 1 + ((NumElements - 1) / MaxLen);
+  // Split the very long directives into several parts if the limit is
+  // specified.
+  for (unsigned I = 0; I < NumChunks; ++I) {
+    SmallString<128> Str;
+    raw_svector_ostream OS(Str);
+
+    const char *Label = Directive;
+    for (auto It = std::next(Data.bytes_begin(), I * MaxLen),
+              End = (I == NumChunks - 1)
+                        ? Data.bytes_end()
+                        : std::next(Data.bytes_begin(), (I + 1) * MaxLen);
+         It != End; ++It) {
+      OS << Label << (unsigned)*It;
+      if (Label == Directive)
+        Label = ",";
+    }
+    Streamer.EmitRawText(OS.str());
+  }
+}
+
diff --git a/llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXTargetStreamer.h b/llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXTargetStreamer.h
index 30831ab8..34391a8 100644
--- a/llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXTargetStreamer.h
+++ b/llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXTargetStreamer.h
@@ -39,6 +39,10 @@ public:
   void emitDwarfFileDirective(StringRef Directive) override;
   void changeSection(const MCSection *CurSection, MCSection *Section,
                      const MCExpr *SubSection, raw_ostream &OS) override;
+  /// Emit the bytes in \p Data into the output.
+  ///
+  /// This is used to emit bytes in \p Data as sequence of .byte directives.
+  void emitRawBytes(StringRef Data) override;
 };
 
 } // end namespace llvm