Micro-optimization: don't shift an entire bitcode record over to get the code.
Previously, BitstreamCursor read an abbreviated record by splatting the
whole thing into a data vector, then extracting and removing the /first/
element. Now, it reads the first element--the record code--separately from
the actual field values.
No (intended) functionality change.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181639 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Bitcode/Reader/BitstreamReader.cpp b/lib/Bitcode/Reader/BitstreamReader.cpp
index 9dafe2a..1fd9abd 100644
--- a/lib/Bitcode/Reader/BitstreamReader.cpp
+++ b/lib/Bitcode/Reader/BitstreamReader.cpp
@@ -204,7 +204,16 @@
const BitCodeAbbrev *Abbv = getAbbrev(AbbrevID);
- for (unsigned i = 0, e = Abbv->getNumOperandInfos(); i != e; ++i) {
+ // Read the record code first.
+ assert(Abbv->getNumOperandInfos() != 0 && "no record code in abbreviation?");
+ const BitCodeAbbrevOp &CodeOp = Abbv->getOperandInfo(0);
+ if (CodeOp.isLiteral())
+ readAbbreviatedLiteral(CodeOp, Vals);
+ else
+ readAbbreviatedField(CodeOp, Vals);
+ unsigned Code = (unsigned)Vals.pop_back_val();
+
+ for (unsigned i = 1, e = Abbv->getNumOperandInfos(); i != e; ++i) {
const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i);
if (Op.isLiteral()) {
readAbbreviatedLiteral(Op, Vals);
@@ -264,8 +273,6 @@
JumpToBit(NewEnd);
}
- unsigned Code = (unsigned)Vals[0];
- Vals.erase(Vals.begin());
return Code;
}