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Micro-optimization: don't shift an entire bitcode record over to get the code.

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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
This commit is contained in:
Jordan Rose 2013-05-10 22:17:10 +00:00
parent acd1d031b8
commit 1197e38f33
1 changed files with 10 additions and 3 deletions
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13
lib/Bitcode/Reader/BitstreamReader.cpp
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@ -204,7 +204,16 @@ unsigned BitstreamCursor::readRecord(unsigned AbbrevID,
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 @@ unsigned BitstreamCursor::readRecord(unsigned AbbrevID,
JumpToBit(NewEnd);
}
unsigned Code = (unsigned)Vals[0];
Vals.erase(Vals.begin());
return Code;
}