From b24f5b7c0838f22abc6f1ba5de2a17d25293cd17 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Sat, 9 Feb 2013 07:07:29 +0000 Subject: Fix the underlying problem that was causing read(0) to be called: sometimes the bitcode writer would generate abbrev records saying that the abbrev should be filled with fixed zero-bit bitfields (this happens in the .bc writer when the number of types used in a module is exactly one, since log2(1) == 0). In this case, just handle it as a literal zero. We can't "just fix" the writer without breaking compatibility with existing bc files, so have the abbrev reader do the substitution. Strengthen the assert in read to reject reads of zero bits so we catch such crimes in the future, and remove the special case designed to handle this. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174801 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Bitcode/Reader/BitstreamReader.cpp | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) (limited to 'lib/Bitcode/Reader') diff --git a/lib/Bitcode/Reader/BitstreamReader.cpp b/lib/Bitcode/Reader/BitstreamReader.cpp index 85076f3..b133502 100644 --- a/lib/Bitcode/Reader/BitstreamReader.cpp +++ b/lib/Bitcode/Reader/BitstreamReader.cpp @@ -288,9 +288,20 @@ void BitstreamCursor::ReadAbbrevRecord() { } BitCodeAbbrevOp::Encoding E = (BitCodeAbbrevOp::Encoding)Read(3); - if (BitCodeAbbrevOp::hasEncodingData(E)) - Abbv->Add(BitCodeAbbrevOp(E, ReadVBR64(5))); - else + if (BitCodeAbbrevOp::hasEncodingData(E)) { + unsigned Data = ReadVBR64(5); + + // As a special case, handle fixed(0) (i.e., a fixed field with zero bits) + // and vbr(0) as a literal zero. This is decoded the same way, and avoids + // a slow path in Read() to have to handle reading zero bits. + if ((E == BitCodeAbbrevOp::Fixed || E == BitCodeAbbrevOp::VBR) && + Data == 0) { + Abbv->Add(BitCodeAbbrevOp(0)); + continue; + } + + Abbv->Add(BitCodeAbbrevOp(E, Data)); + } else Abbv->Add(BitCodeAbbrevOp(E)); } CurAbbrevs.push_back(Abbv); -- cgit v1.1