Reapply ~"Bitcode: Collect all MDString records into a single blob"
Spiritually reapply commit r264409 (reverted in r264410), albeit with a
bit of a redesign.
Firstly, avoid splitting the big blob into multiple chunks of strings.
r264409 imposed an arbitrary limit to avoid a massive allocation on the
shared 'Record' SmallVector. The bug with that commit only reproduced
when there were more than "chunk-size" strings. A test for this would
have been useless long-term, since we're liable to adjust the chunk-size
in the future.
Thus, eliminate the motivation for chunk-ing by storing the string sizes
in the blob. Here's the layout:
vbr6: # of strings
vbr6: offset-to-blob
blob:
[vbr6]: string lengths
[char]: concatenated strings
Secondly, make the output of llvm-bcanalyzer readable.
I noticed when debugging r264409 that llvm-bcanalyzer was outputting a
massive blob all in one line. Past a small number, the strings were
impossible to split in my head, and the lines were way too long. This
version adds support in llvm-bcanalyzer for pretty-printing.
<STRINGS abbrevid=4 op0=3 op1=9/> num-strings = 3 {
'abc'
'def'
'ghi'
}
From the original commit:
Inspired by Mehdi's similar patch, http://reviews.llvm.org/D18342, this
should (a) slightly reduce bitcode size, since there is less record
overhead, and (b) greatly improve reading speed, since blobs are super
cheap to deserialize.
llvm-svn: 264551
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index bb479db..cb2784f 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -396,6 +396,9 @@
std::error_code globalCleanup();
std::error_code resolveGlobalAndAliasInits();
std::error_code parseMetadata(bool ModuleLevel = false);
+ std::error_code parseMetadataStrings(ArrayRef<uint64_t> Record,
+ StringRef Blob,
+ unsigned &NextMetadataNo);
std::error_code parseMetadataKinds();
std::error_code parseMetadataKindRecord(SmallVectorImpl<uint64_t> &Record);
std::error_code parseMetadataAttachment(Function &F);
@@ -1883,6 +1886,47 @@
static int64_t unrotateSign(uint64_t U) { return U & 1 ? ~(U >> 1) : U >> 1; }
+std::error_code BitcodeReader::parseMetadataStrings(ArrayRef<uint64_t> Record,
+ StringRef Blob,
+ unsigned &NextMetadataNo) {
+ // All the MDStrings in the block are emitted together in a single
+ // record. The strings are concatenated and stored in a blob along with
+ // their sizes.
+ if (Record.size() != 2)
+ return error("Invalid record: metadata strings layout");
+
+ unsigned NumStrings = Record[0];
+ unsigned StringsOffset = Record[1];
+ if (!NumStrings)
+ return error("Invalid record: metadata strings with no strings");
+ if (StringsOffset >= Blob.size())
+ return error("Invalid record: metadata strings corrupt offset");
+
+ StringRef Lengths = Blob.slice(0, StringsOffset);
+ SimpleBitstreamCursor R(*StreamFile);
+ R.jumpToPointer(Lengths.begin());
+
+ // Ensure that Blob doesn't get invalidated, even if this is reading from
+ // a StreamingMemoryObject with corrupt data.
+ R.setArtificialByteLimit(R.getCurrentByteNo() + StringsOffset);
+
+ StringRef Strings = Blob.drop_front(StringsOffset);
+ do {
+ if (R.AtEndOfStream())
+ return error("Invalid record: metadata strings bad length");
+
+ unsigned Size = R.ReadVBR(6);
+ if (Strings.size() < Size)
+ return error("Invalid record: metadata strings truncated chars");
+
+ MetadataList.assignValue(MDString::get(Context, Strings.slice(0, Size)),
+ NextMetadataNo++);
+ Strings = Strings.drop_front(Size);
+ } while (--NumStrings);
+
+ return std::error_code();
+}
+
/// Parse a METADATA_BLOCK. If ModuleLevel is true then we are parsing
/// module level metadata.
std::error_code BitcodeReader::parseMetadata(bool ModuleLevel) {
@@ -1929,7 +1973,8 @@
// Read a record.
Record.clear();
- unsigned Code = Stream.readRecord(Entry.ID, Record);
+ StringRef Blob;
+ unsigned Code = Stream.readRecord(Entry.ID, Record, &Blob);
bool IsDistinct = false;
switch (Code) {
default: // Default behavior: ignore.
@@ -2363,7 +2408,7 @@
NextMetadataNo++);
break;
}
- case bitc::METADATA_STRING: {
+ case bitc::METADATA_STRING_OLD: {
std::string String(Record.begin(), Record.end());
// Test for upgrading !llvm.loop.
@@ -2373,6 +2418,11 @@
MetadataList.assignValue(MD, NextMetadataNo++);
break;
}
+ case bitc::METADATA_STRINGS:
+ if (std::error_code EC =
+ parseMetadataStrings(Record, Blob, NextMetadataNo))
+ return EC;
+ break;
case bitc::METADATA_KIND: {
// Support older bitcode files that had METADATA_KIND records in a
// block with METADATA_BLOCK_ID.