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Fix a compile time regression caused by too small hash tables. 

Measure the worst case number of probes for a miss instead of the less
conservative number of probes required for an insertion.

Lower the limit to < 6 probes worst case.

This doubles the size of the ARM and X86 hash tables, other targets are
unaffected. LiveVariables runs 12% faster with this change.

<rdar://problem/9598545>

llvm-svn: 132999
This commit is contained in:
Jakob Stoklund Olesen 2011-06-14 16:58:16 +00:00
parent d1cff77200
commit 01eada6e5c
1 changed files with 16 additions and 3 deletions
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19
llvm/utils/TableGen/RegisterInfoEmitter.cpp
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@ -145,7 +145,6 @@ static void generateHashTable(raw_ostream &OS, const char *Name,
HT.assign(HSize, Sentinel); HT.assign(HSize, Sentinel);
// Insert all entries. // Insert all entries.
MaxProbes = 0;
for (unsigned i = 0, e = Data.size(); i != e; ++i) { for (unsigned i = 0, e = Data.size(); i != e; ++i) {
UUPair D = Data[i]; UUPair D = Data[i];
unsigned Idx = (D.first * 11 + D.second * 97) & (HSize - 1); unsigned Idx = (D.first * 11 + D.second * 97) & (HSize - 1);
@ -155,10 +154,24 @@ static void generateHashTable(raw_ostream &OS, const char *Name,
ProbeAmt += 1; ProbeAmt += 1;
} }
HT[Idx] = D; HT[Idx] = D;
}
// Now measure the max number of probes for any worst case miss.
MaxProbes = 0;
unsigned TotalProbes = 0;
for (unsigned i = 0, e = HSize; i != e; ++i) {
unsigned Idx = i;
unsigned ProbeAmt = 1;
while (HT[Idx] != Sentinel) {
Idx = (Idx + ProbeAmt) & (HSize - 1);
ProbeAmt += 1;
}
TotalProbes += ProbeAmt;
MaxProbes = std::max(MaxProbes, ProbeAmt); MaxProbes = std::max(MaxProbes, ProbeAmt);
} }
OS << "\n // Max number of probes: " << MaxProbes; OS << "\n // Max number of probes: " << MaxProbes
} while (MaxProbes >= 8); << format(", avg %.1f", float(TotalProbes)/HSize);
} while (MaxProbes >= 6);
// Print the hash table. // Print the hash table.
OS << "\n // Used entries: " << Data.size() OS << "\n // Used entries: " << Data.size()