r176567 - [PCH] When pre-validating the headers from the PCH, only validate non-system headers.
Argyrios Kyrtzidis
akyrtzi at gmail.com
Wed Mar 6 10:12:50 PST 2013
Author: akirtzidis
Date: Wed Mar 6 12:12:50 2013
New Revision: 176567
URL: http://llvm.org/viewvc/llvm-project?rev=176567&view=rev
Log:
[PCH] When pre-validating the headers from the PCH, only validate non-system headers.
Stat'ing all the headers from the PCH to make sure they are up-to-date takes significant time.
In a particular source file (whose PCH file included Cocoa.h) from total -fsyntax-only time
12% was just stat calls. Change pre-validation to only check non-system headers.
There are some notable disadvantages:
-If a system header, that is not include-guarded, changes after the PCH was created, we will not
find it in the header info table and we will #import it, effectively #importing it twice, thus
we will emit some error due to a multiple definition and after that the "header was modified" error will likely
be emitted, for example something like:
NSDictionary.h:12:1: error: duplicate interface definition for class 'NSDictionary'
@interface NSDictionary : NSObject <NSCopying, NSMutableCopying, NSSecureCoding, NSFastEnumeration>
^
NSDictionary.h:12:12: note: previous definition is here
@interface NSDictionary : NSObject <NSCopying, NSMutableCopying, NSSecureCoding, NSFastEnumeration>
^
fatal error: file 'NSDictionary.h' has been modified since the precompiled header was built
Though we get the "header was modified" error, this is a bit confusing.
-Theoretically it is possible that such a system header will cause no errors but it will just cause an
unfortunate semantic change, though I find this rather unlikely.
The advantages:
-Reduces compilation time when using a huge PCH like the Cocoa ones
-System headers change very infrequent and when they do, users/build systems should be able to know that
re-building from scratch is needed.
Addresses rdar://13056262
Modified:
cfe/trunk/lib/Serialization/ASTReader.cpp
cfe/trunk/lib/Serialization/ASTWriter.cpp
Modified: cfe/trunk/lib/Serialization/ASTReader.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Serialization/ASTReader.cpp?rev=176567&r1=176566&r2=176567&view=diff
==============================================================================
--- cfe/trunk/lib/Serialization/ASTReader.cpp (original)
+++ cfe/trunk/lib/Serialization/ASTReader.cpp Wed Mar 6 12:12:50 2013
@@ -1680,10 +1680,12 @@ ASTReader::ReadControlBlock(ModuleFile &
Error("malformed block record in AST file");
return Failure;
case llvm::BitstreamEntry::EndBlock:
- // Validate all of the input files.
+ // Validate all of the non-system input files.
if (!DisableValidation) {
bool Complain = (ClientLoadCapabilities & ARR_OutOfDate) == 0;
- for (unsigned I = 0, N = Record[0]; I < N; ++I) {
+ // All user input files reside at the index range [0, Record[1]).
+ // Record is the one from INPUT_FILE_OFFSETS.
+ for (unsigned I = 0, N = Record[1]; I < N; ++I) {
InputFile IF = getInputFile(F, I+1, Complain);
if (!IF.getFile() || IF.isOutOfDate())
return OutOfDate;
Modified: cfe/trunk/lib/Serialization/ASTWriter.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Serialization/ASTWriter.cpp?rev=176567&r1=176566&r2=176567&view=diff
==============================================================================
--- cfe/trunk/lib/Serialization/ASTWriter.cpp (original)
+++ cfe/trunk/lib/Serialization/ASTWriter.cpp Wed Mar 6 12:12:50 2013
@@ -1232,8 +1232,9 @@ void ASTWriter::WriteInputFiles(SourceMa
IFAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob)); // File name
unsigned IFAbbrevCode = Stream.EmitAbbrev(IFAbbrev);
- // Write out all of the input files.
- std::vector<uint32_t> InputFileOffsets;
+ // Get all ContentCache objects for files, sorted by whether the file is a
+ // system one or not. System files go at the back, users files at the front.
+ std::deque<const SrcMgr::ContentCache *> SortedFiles;
for (unsigned I = 1, N = SourceMgr.local_sloc_entry_size(); I != N; ++I) {
// Get this source location entry.
const SrcMgr::SLocEntry *SLoc = &SourceMgr.getLocalSLocEntry(I);
@@ -1246,6 +1247,19 @@ void ASTWriter::WriteInputFiles(SourceMa
if (!Cache->OrigEntry)
continue;
+ if (Cache->IsSystemFile)
+ SortedFiles.push_back(Cache);
+ else
+ SortedFiles.push_front(Cache);
+ }
+
+ unsigned UserFilesNum = 0;
+ // Write out all of the input files.
+ std::vector<uint32_t> InputFileOffsets;
+ for (std::deque<const SrcMgr::ContentCache *>::iterator
+ I = SortedFiles.begin(), E = SortedFiles.end(); I != E; ++I) {
+ const SrcMgr::ContentCache *Cache = *I;
+
uint32_t &InputFileID = InputFileIDs[Cache->OrigEntry];
if (InputFileID != 0)
continue; // already recorded this file.
@@ -1255,6 +1269,9 @@ void ASTWriter::WriteInputFiles(SourceMa
InputFileID = InputFileOffsets.size();
+ if (!Cache->IsSystemFile)
+ ++UserFilesNum;
+
Record.clear();
Record.push_back(INPUT_FILE);
Record.push_back(InputFileOffsets.size());
@@ -1290,6 +1307,8 @@ void ASTWriter::WriteInputFiles(SourceMa
BitCodeAbbrev *OffsetsAbbrev = new BitCodeAbbrev();
OffsetsAbbrev->Add(BitCodeAbbrevOp(INPUT_FILE_OFFSETS));
OffsetsAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // # input files
+ OffsetsAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // # non-system
+ // input files
OffsetsAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob)); // Array
unsigned OffsetsAbbrevCode = Stream.EmitAbbrev(OffsetsAbbrev);
@@ -1297,6 +1316,7 @@ void ASTWriter::WriteInputFiles(SourceMa
Record.clear();
Record.push_back(INPUT_FILE_OFFSETS);
Record.push_back(InputFileOffsets.size());
+ Record.push_back(UserFilesNum);
Stream.EmitRecordWithBlob(OffsetsAbbrevCode, Record, data(InputFileOffsets));
}
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