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
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 @@
}
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);