From a61f5e379675732666744bcba25efbc9922e016a Mon Sep 17 00:00:00 2001
From: Teresa Johnson <tejohnson@google.com>
Date: Fri, 16 Dec 2016 21:25:01 +0000
Subject: [ThinLTO] Import composite types as declarations

Summary:
When reading the metadata bitcode, create a type declaration when
possible for composite types when we are importing. Doing this in
the bitcode reader saves memory. Also it works naturally in the case
when the type ODR map contains a definition for the same composite type
because it was used in the importing module (buildODRType will
automatically use the existing definition and not create a type
declaration).

For Chromium built with -g2, this reduces the aggregate size of the
generated native object files by 66% (from 31G to 10G). It reduced
the time through the ThinLTO link and backend phases by about 20% on
my machine.

Reviewers: mehdi_amini, dblaikie, aprantl

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D27775

llvm-svn: 289993
---
 llvm/lib/Bitcode/Reader/BitcodeReader.cpp | 37 +++++++++++++++++--------------
 1 file changed, 20 insertions(+), 17 deletions(-)

(limited to 'llvm/lib/Bitcode/Reader/BitcodeReader.cpp')

diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index ad4d9ce..4812b2c 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -488,7 +488,8 @@ public:
 
   /// \brief Main interface to parsing a bitcode buffer.
   /// \returns true if an error occurred.
-  Error parseBitcodeInto(Module *M, bool ShouldLazyLoadMetadata = false);
+  Error parseBitcodeInto(Module *M, bool ShouldLazyLoadMetadata = false,
+                         bool IsImporting = false);
 
   static uint64_t decodeSignRotatedValue(uint64_t V);
 
@@ -3084,9 +3085,10 @@ Error BitcodeReader::parseModule(uint64_t ResumeBit,
   }
 }
 
-Error BitcodeReader::parseBitcodeInto(Module *M, bool ShouldLazyLoadMetadata) {
+Error BitcodeReader::parseBitcodeInto(Module *M, bool ShouldLazyLoadMetadata,
+                                      bool IsImporting) {
   TheModule = M;
-  MDLoader = MetadataLoader(Stream, *M, ValueList,
+  MDLoader = MetadataLoader(Stream, *M, ValueList, IsImporting,
                             [&](unsigned ID) { return getTypeByID(ID); });
   return parseModule(0, ShouldLazyLoadMetadata);
 }
@@ -5220,7 +5222,7 @@ llvm::getBitcodeModuleList(MemoryBufferRef Buffer) {
 /// everything.
 Expected<std::unique_ptr<Module>>
 BitcodeModule::getModuleImpl(LLVMContext &Context, bool MaterializeAll,
-                             bool ShouldLazyLoadMetadata) {
+                             bool ShouldLazyLoadMetadata, bool IsImporting) {
   BitstreamCursor Stream(Buffer);
 
   std::string ProducerIdentification;
@@ -5243,7 +5245,8 @@ BitcodeModule::getModuleImpl(LLVMContext &Context, bool MaterializeAll,
   M->setMaterializer(R);
 
   // Delay parsing Metadata if ShouldLazyLoadMetadata is true.
-  if (Error Err = R->parseBitcodeInto(M.get(), ShouldLazyLoadMetadata))
+  if (Error Err =
+          R->parseBitcodeInto(M.get(), ShouldLazyLoadMetadata, IsImporting))
     return std::move(Err);
 
   if (MaterializeAll) {
@@ -5259,9 +5262,9 @@ BitcodeModule::getModuleImpl(LLVMContext &Context, bool MaterializeAll,
 }
 
 Expected<std::unique_ptr<Module>>
-BitcodeModule::getLazyModule(LLVMContext &Context,
-                             bool ShouldLazyLoadMetadata) {
-  return getModuleImpl(Context, false, ShouldLazyLoadMetadata);
+BitcodeModule::getLazyModule(LLVMContext &Context, bool ShouldLazyLoadMetadata,
+                             bool IsImporting) {
+  return getModuleImpl(Context, false, ShouldLazyLoadMetadata, IsImporting);
 }
 
 // Parse the specified bitcode buffer, returning the function info index.
@@ -5323,20 +5326,20 @@ static Expected<BitcodeModule> getSingleModule(MemoryBufferRef Buffer) {
 }
 
 Expected<std::unique_ptr<Module>>
-llvm::getLazyBitcodeModule(MemoryBufferRef Buffer,
-                           LLVMContext &Context, bool ShouldLazyLoadMetadata) {
+llvm::getLazyBitcodeModule(MemoryBufferRef Buffer, LLVMContext &Context,
+                           bool ShouldLazyLoadMetadata, bool IsImporting) {
   Expected<BitcodeModule> BM = getSingleModule(Buffer);
   if (!BM)
     return BM.takeError();
 
-  return BM->getLazyModule(Context, ShouldLazyLoadMetadata);
+  return BM->getLazyModule(Context, ShouldLazyLoadMetadata, IsImporting);
 }
 
-Expected<std::unique_ptr<Module>>
-llvm::getOwningLazyBitcodeModule(std::unique_ptr<MemoryBuffer> &&Buffer,
-                                 LLVMContext &Context,
-                                 bool ShouldLazyLoadMetadata) {
-  auto MOrErr = getLazyBitcodeModule(*Buffer, Context, ShouldLazyLoadMetadata);
+Expected<std::unique_ptr<Module>> llvm::getOwningLazyBitcodeModule(
+    std::unique_ptr<MemoryBuffer> &&Buffer, LLVMContext &Context,
+    bool ShouldLazyLoadMetadata, bool IsImporting) {
+  auto MOrErr = getLazyBitcodeModule(*Buffer, Context, ShouldLazyLoadMetadata,
+                                     IsImporting);
   if (MOrErr)
     (*MOrErr)->setOwnedMemoryBuffer(std::move(Buffer));
   return MOrErr;
@@ -5344,7 +5347,7 @@ llvm::getOwningLazyBitcodeModule(std::unique_ptr<MemoryBuffer> &&Buffer,
 
 Expected<std::unique_ptr<Module>>
 BitcodeModule::parseModule(LLVMContext &Context) {
-  return getModuleImpl(Context, true, false);
+  return getModuleImpl(Context, true, false, false);
   // TODO: Restore the use-lists to the in-memory state when the bitcode was
   // written.  We must defer until the Module has been fully materialized.
 }
-- 
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