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authorDouglas Gregor <dgregor@apple.com>2009-04-25 21:21:38 +0000
committerDouglas Gregor <dgregor@apple.com>2009-04-25 21:21:38 +0000
commit17e1c5eba505d0c99e35aa6143631653db668fb6 (patch)
tree16353db3de42d3d9d9686b8729bfca9bb89de6e5 /lib/Frontend
parentd6595a40fe12e3d5ffe5ce48987b379d547439a4 (diff)
Optimize the loading of an identifier from a PCH file when given the
identifier's ID. In this case, we know where the identifier's entry is located in the hash table (it starts right before the identifier string itself), so skip the hash table lookup and read the entry directly. The performance improvement here is, gain, hard to quantify, but it's the right thing to do. git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@70078 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Frontend')
-rw-r--r--lib/Frontend/PCHReader.cpp52
1 files changed, 35 insertions, 17 deletions
diff --git a/lib/Frontend/PCHReader.cpp b/lib/Frontend/PCHReader.cpp
index 6f1ff32977..40e5c0d603 100644
--- a/lib/Frontend/PCHReader.cpp
+++ b/lib/Frontend/PCHReader.cpp
@@ -2842,6 +2842,7 @@ IdentifierInfo *PCHReader::DecodeIdentifierInfo(unsigned ID) {
if (!IdentifiersLoaded[ID - 1]) {
uint32_t Offset = IdentifierOffsets[ID - 1];
+ const char *Str = IdentifierTableData + Offset;
// If there is an identifier lookup table, but the offset of this
// string is after the identifier table itself, then we know that
@@ -2850,23 +2851,40 @@ IdentifierInfo *PCHReader::DecodeIdentifierInfo(unsigned ID) {
// identifier.
PCHIdentifierLookupTable *IdTable
= (PCHIdentifierLookupTable *)IdentifierLookupTable;
- bool SkipHashTable = IdTable &&
- Offset >= uint32_t(IdTable->getBuckets() - IdTable->getBase());
-
- if (SkipHashTable)
- PP.getIdentifierTable().setExternalIdentifierLookup(0);
-
- // All of the strings in the PCH file are preceded by a 16-bit
- // length. Extract that 16-bit length to avoid having to run
- // strlen().
- const char *Str = IdentifierTableData + Offset;
- const char *StrLenPtr = Str - 2;
- unsigned StrLen = (((unsigned) StrLenPtr[0])
- | (((unsigned) StrLenPtr[1]) << 8)) - 1;
- IdentifiersLoaded[ID - 1] = &Context.Idents.get(Str, Str + StrLen);
-
- if (SkipHashTable)
- PP.getIdentifierTable().setExternalIdentifierLookup(this);
+ if (!IdTable ||
+ Offset >= uint32_t(IdTable->getBuckets() - IdTable->getBase())) {
+ // Turn off lookup into the on-disk hash table. We know that
+ // this identifier is not there.
+ if (IdTable)
+ PP.getIdentifierTable().setExternalIdentifierLookup(0);
+
+ // All of the strings in the PCH file are preceded by a 16-bit
+ // length. Extract that 16-bit length to avoid having to execute
+ // strlen().
+ const char *StrLenPtr = Str - 2;
+ unsigned StrLen = (((unsigned) StrLenPtr[0])
+ | (((unsigned) StrLenPtr[1]) << 8)) - 1;
+ IdentifiersLoaded[ID - 1] = &Context.Idents.get(Str, Str + StrLen);
+
+ // Turn on lookup into the on-disk hash table, if we have an
+ // on-disk hash table.
+ if (IdTable)
+ PP.getIdentifierTable().setExternalIdentifierLookup(this);
+ } else {
+ // The identifier is a key in our on-disk hash table. Since we
+ // know where the hash table entry starts, just read in this
+ // (key, value) pair.
+ PCHIdentifierLookupTrait Trait(const_cast<PCHReader &>(*this));
+ const unsigned char *Pos = (const unsigned char *)Str - 4;
+ std::pair<unsigned, unsigned> KeyDataLengths
+ = Trait.ReadKeyDataLength(Pos);
+
+ PCHIdentifierLookupTrait::internal_key_type InternalKey
+ = Trait.ReadKey(Pos, KeyDataLengths.first);
+ Pos = (const unsigned char *)Str + KeyDataLengths.first;
+ IdentifiersLoaded[ID - 1] = Trait.ReadData(InternalKey, Pos,
+ KeyDataLengths.second);
+ }
}
return IdentifiersLoaded[ID - 1];