[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

1 files changed, 39 insertions, 0 deletions

diff --git a/llvm/unittests/Remarks/RemarksStrTabParsingTest.cpp b/llvm/unittests/Remarks/RemarksStrTabParsingTest.cpp
new file mode 100644
index 00000000000..f1e9eb86840
--- /dev/null
+++ b/llvm/unittests/Remarks/RemarksStrTabParsingTest.cpp
@@ -0,0 +1,39 @@
+//===- unittest/Support/RemarksStrTabParsingTest.cpp - StrTab tests -------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Remarks/Remark.h"
+#include "llvm/Remarks/RemarkParser.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+TEST(RemarksStrTab, ParsingEmpty) {
+  StringRef Empty("", 0);
+  remarks::ParsedStringTable StrTab(Empty);
+  Expected<StringRef> Nothing = StrTab[0];
+  EXPECT_FALSE(static_cast<bool>(Nothing));
+  EXPECT_EQ(toString(Nothing.takeError()),
+            "String with index 0 is out of bounds (size = 0).");
+}
+
+TEST(RemarksStrTab, ParsingGood) {
+  StringRef Strings("str1\0str2\0str3\0str4", 20);
+  remarks::ParsedStringTable StrTab(Strings);
+  Expected<StringRef> Result = StrTab[0];
+  EXPECT_TRUE(static_cast<bool>(Result));
+  EXPECT_EQ(*Result, "str1");
+  Result = StrTab[1];
+  EXPECT_TRUE(static_cast<bool>(Result));
+  EXPECT_EQ(*Result, "str2");
+  Result = StrTab[2];
+  EXPECT_TRUE(static_cast<bool>(Result));
+  EXPECT_EQ(*Result, "str3");
+  Result = StrTab[3];
+  EXPECT_TRUE(static_cast<bool>(Result));
+  EXPECT_EQ(*Result, "str4");
+}