From b523790ae1b30a1708d2fc7937f90e283330ef33 Mon Sep 17 00:00:00 2001
From: Wei Mi <wmi@google.com>
Date: Mon, 7 Oct 2019 16:12:37 +0000
Subject: [SampleFDO] Add compression support for any section in ExtBinary
 profile format

Previously ExtBinary profile format only supports compression using zlib for
profile symbol list. In this patch, we extend the compression support to any
section. User can select some or all of the sections to compress. In an
experiment, for a 45M profile in ExtBinary format, compressing name table
reduced its size to 24M, and compressing all the sections reduced its size
to 11M.

Differential Revision: https://reviews.llvm.org/D68253

llvm-svn: 373914
---
 llvm/lib/ProfileData/SampleProfReader.cpp | 84 +++++++++++++++++++++++--------
 1 file changed, 63 insertions(+), 21 deletions(-)

(limited to 'llvm/lib/ProfileData/SampleProfReader.cpp')

diff --git a/llvm/lib/ProfileData/SampleProfReader.cpp b/llvm/lib/ProfileData/SampleProfReader.cpp
index 07272ebac0a..075bd9412b0 100644
--- a/llvm/lib/ProfileData/SampleProfReader.cpp
+++ b/llvm/lib/ProfileData/SampleProfReader.cpp
@@ -26,6 +26,7 @@
 #include "llvm/IR/ProfileSummary.h"
 #include "llvm/ProfileData/ProfileCommon.h"
 #include "llvm/ProfileData/SampleProf.h"
+#include "llvm/Support/Compression.h"
 #include "llvm/Support/ErrorOr.h"
 #include "llvm/Support/LEB128.h"
 #include "llvm/Support/LineIterator.h"
@@ -471,6 +472,7 @@ std::error_code
 SampleProfileReaderExtBinary::readOneSection(const uint8_t *Start,
                                              uint64_t Size, SecType Type) {
   Data = Start;
+  End = Start + Size;
   switch (Type) {
   case SecProfSummary:
     if (std::error_code EC = readSummary())
@@ -487,7 +489,7 @@ SampleProfileReaderExtBinary::readOneSection(const uint8_t *Start,
     }
     break;
   case SecProfileSymbolList:
-    if (std::error_code EC = readProfileSymbolList())
+    if (std::error_code EC = readProfileSymbolList(Size))
       return EC;
     break;
   default:
@@ -496,27 +498,43 @@ SampleProfileReaderExtBinary::readOneSection(const uint8_t *Start,
   return sampleprof_error::success;
 }
 
-std::error_code SampleProfileReaderExtBinary::readProfileSymbolList() {
-  auto UncompressSize = readNumber<uint64_t>();
-  if (std::error_code EC = UncompressSize.getError())
-    return EC;
+std::error_code
+SampleProfileReaderExtBinary::readProfileSymbolList(uint64_t Size) {
+  if (!ProfSymList)
+    ProfSymList = std::make_unique<ProfileSymbolList>();
 
-  auto CompressSize = readNumber<uint64_t>();
-  if (std::error_code EC = CompressSize.getError())
+  if (std::error_code EC = ProfSymList->read(Data, Size))
     return EC;
 
-  if (!ProfSymList)
-    ProfSymList = std::make_unique<ProfileSymbolList>();
+  Data = Data + Size;
+  return sampleprof_error::success;
+}
 
-  if (std::error_code EC =
-          ProfSymList->read(*CompressSize, *UncompressSize, Data))
+std::error_code SampleProfileReaderExtBinaryBase::decompressSection(
+    const uint8_t *SecStart, const uint64_t SecSize,
+    const uint8_t *&DecompressBuf, uint64_t &DecompressBufSize) {
+  Data = SecStart;
+  End = SecStart + SecSize;
+  auto DecompressSize = readNumber<uint64_t>();
+  if (std::error_code EC = DecompressSize.getError())
     return EC;
+  DecompressBufSize = *DecompressSize;
 
-  // CompressSize is zero only when ProfileSymbolList is not compressed.
-  if (*CompressSize == 0)
-    Data = Data + *UncompressSize;
-  else
-    Data = Data + *CompressSize;
+  auto CompressSize = readNumber<uint64_t>();
+  if (std::error_code EC = CompressSize.getError())
+    return EC;
+
+  if (!llvm::zlib::isAvailable())
+    return sampleprof_error::zlib_unavailable;
+
+  StringRef CompressedStrings(reinterpret_cast<const char *>(Data),
+                              *CompressSize);
+  char *Buffer = Allocator.Allocate<char>(DecompressBufSize);
+  llvm::Error E =
+      zlib::uncompress(CompressedStrings, Buffer, DecompressBufSize);
+  if (E)
+    return sampleprof_error::uncompress_failed;
+  DecompressBuf = reinterpret_cast<const uint8_t *>(Buffer);
   return sampleprof_error::success;
 }
 
@@ -528,11 +546,35 @@ std::error_code SampleProfileReaderExtBinaryBase::read() {
     // Skip empty section.
     if (!Entry.Size)
       continue;
+
     const uint8_t *SecStart = BufStart + Entry.Offset;
-    if (std::error_code EC = readOneSection(SecStart, Entry.Size, Entry.Type))
+    uint64_t SecSize = Entry.Size;
+
+    // If the section is compressed, decompress it into a buffer
+    // DecompressBuf before reading the actual data. The pointee of
+    // 'Data' will be changed to buffer hold by DecompressBuf
+    // temporarily when reading the actual data.
+    bool isCompressed = hasSecFlag(Entry, SecFlagCompress);
+    if (isCompressed) {
+      const uint8_t *DecompressBuf;
+      uint64_t DecompressBufSize;
+      if (std::error_code EC = decompressSection(
+              SecStart, SecSize, DecompressBuf, DecompressBufSize))
+        return EC;
+      SecStart = DecompressBuf;
+      SecSize = DecompressBufSize;
+    }
+
+    if (std::error_code EC = readOneSection(SecStart, SecSize, Entry.Type))
       return EC;
-    if (Data != SecStart + Entry.Size)
+    if (Data != SecStart + SecSize)
       return sampleprof_error::malformed;
+
+    // Change the pointee of 'Data' from DecompressBuf to original Buffer.
+    if (isCompressed) {
+      Data = BufStart + Entry.Offset;
+      End = BufStart + Buffer->getBufferSize();
+    }
   }
 
   return sampleprof_error::success;
@@ -621,10 +663,10 @@ std::error_code SampleProfileReaderExtBinaryBase::readSecHdrTableEntry() {
     return EC;
   Entry.Type = static_cast<SecType>(*Type);
 
-  auto Flag = readUnencodedNumber<uint64_t>();
-  if (std::error_code EC = Flag.getError())
+  auto Flags = readUnencodedNumber<uint64_t>();
+  if (std::error_code EC = Flags.getError())
     return EC;
-  Entry.Flag = *Flag;
+  Entry.Flags = *Flags;
 
   auto Offset = readUnencodedNumber<uint64_t>();
   if (std::error_code EC = Offset.getError())
-- 
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