[Remarks] Add string deduplication using a string table

* Add support for uniquing strings in the remark streamer and emitting the string table in the remarks section.

* Add parsing support for the string table in the RemarkParser.

From this remark:

```
--- !Missed
Pass:     inline
Name:     NoDefinition
DebugLoc: { File: 'test-suite/SingleSource/UnitTests/2002-04-17-PrintfChar.c',
            Line: 7, Column: 3 }
Function: printArgsNoRet
Args:
  - Callee:   printf
  - String:   ' will not be inlined into '
  - Caller:   printArgsNoRet
    DebugLoc: { File: 'test-suite/SingleSource/UnitTests/2002-04-17-PrintfChar.c',
                Line: 6, Column: 0 }
  - String:   ' because its definition is unavailable'
...
```

to:

```
--- !Missed
Pass: 0
Name: 1
DebugLoc: { File: 3, Line: 7, Column: 3 }
Function: 2
Args:
  - Callee:   4
  - String:   5
  - Caller:   2
    DebugLoc: { File: 3, Line: 6, Column: 0 }
  - String:   6
...
```

And the string table in the .remarks/__remarks section containing:

```
inline\0NoDefinition\0printArgsNoRet\0
test-suite/SingleSource/UnitTests/2002-04-17-PrintfChar.c\0printf\0
will not be inlined into \0 because its definition is unavailable\0
```

This is mostly supposed to be used for testing purposes, but it gives us
a 2x reduction in the remark size, and is an incremental change for the
updates to the remarks file format.

Differential Revision: https://reviews.llvm.org/D60227

llvm-svn: 359050

2 files changed, 24 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 987d324df2c..fc5049b9067 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1362,6 +1362,29 @@ void AsmPrinter::emitRemarksSection(Module &M) {
   support::endian::write64le(Version.data(), remarks::Version);
   OutStreamer->EmitBinaryData(StringRef(Version.data(), Version.size()));
 
+  // Emit the string table in the section.
+  // Note: we need to use the streamer here to emit it in the section. We can't
+  // just use the serialize function with a raw_ostream because of the way
+  // MCStreamers work.
+  const remarks::StringTable &StrTab = RS->getStringTable();
+  std::vector<StringRef> StrTabStrings = StrTab.serialize();
+  uint64_t StrTabSize = StrTab.SerializedSize;
+  // Emit the total size of the string table (the size itself excluded):
+  // little-endian uint64_t.
+  // The total size is located after the version number.
+  std::array<char, 8> StrTabSizeBuf;
+  support::endian::write64le(StrTabSizeBuf.data(), StrTabSize);
+  OutStreamer->EmitBinaryData(
+      StringRef(StrTabSizeBuf.data(), StrTabSizeBuf.size()));
+  // Emit a list of null-terminated strings.
+  // Note: the order is important here: the ID used in the remarks corresponds
+  // to the position of the string in the section.
+  for (StringRef Str : StrTabStrings) {
+    OutStreamer->EmitBytes(Str);
+    // Explicitly emit a '\0'.
+    OutStreamer->EmitIntValue(/*Value=*/0, /*Size=*/1);
+  }
+
   // Emit the null-terminated absolute path to the remark file.
   // The path is located at the offset 0x4 in the section.
   StringRef FilenameRef = RS->getFilename();
diff --git a/llvm/lib/CodeGen/AsmPrinter/LLVMBuild.txt b/llvm/lib/CodeGen/AsmPrinter/LLVMBuild.txt
index 56449269681..44595a18f1b 100644
--- a/llvm/lib/CodeGen/AsmPrinter/LLVMBuild.txt
+++ b/llvm/lib/CodeGen/AsmPrinter/LLVMBuild.txt
@@ -18,4 +18,4 @@
 type = Library
 name = AsmPrinter
 parent = Libraries
-required_libraries = Analysis BinaryFormat CodeGen Core DebugInfoCodeView DebugInfoDWARF DebugInfoMSF MC MCParser Support Target
+required_libraries = Analysis BinaryFormat CodeGen Core DebugInfoCodeView DebugInfoDWARF DebugInfoMSF MC MCParser Remarks Support Target