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[TableGen] Speed up inferMatchingSuperRegClass. NFC. #133060

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merged 1 commit into from
Mar 26, 2025
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[TableGen] Speed up inferMatchingSuperRegClass. NFC. #133060

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25 changes: 15 additions & 10 deletions llvm/utils/TableGen/Common/CodeGenRegisters.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2341,7 +2341,7 @@ void CodeGenRegBank::inferSubClassWithSubReg(CodeGenRegisterClass *RC) {
void CodeGenRegBank::inferMatchingSuperRegClass(
CodeGenRegisterClass *RC,
std::list<CodeGenRegisterClass>::iterator FirstSubRegRC) {
DenseMap<const CodeGenRegister *, std::vector<const CodeGenRegister *>>
std::vector<std::pair<const CodeGenRegister *, const CodeGenRegister *>>
SubToSuperRegs;
BitVector TopoSigs(getNumTopoSigs());

Expand All @@ -2353,15 +2353,17 @@ void CodeGenRegBank::inferMatchingSuperRegClass(
if (RC->getSubClassWithSubReg(&SubIdx) != RC)
continue;

// Build list of (Super, Sub) pairs for this SubIdx.
// Build list of (Sub, Super) pairs for this SubIdx, sorted by Sub. Note
// that the list may contain entries with the same Sub but different Supers.
SubToSuperRegs.clear();
TopoSigs.reset();
for (const auto Super : RC->getMembers()) {
const CodeGenRegister *Sub = Super->getSubRegs().find(&SubIdx)->second;
assert(Sub && "Missing sub-register");
SubToSuperRegs[Sub].push_back(Super);
SubToSuperRegs.emplace_back(Sub, Super);
TopoSigs.set(Sub->getTopoSig());
}
sort(SubToSuperRegs, on_first<deref<std::less<>>>());

// Iterate over sub-register class candidates. Ignore classes created by
// this loop. They will never be useful.
Expand All @@ -2376,14 +2378,17 @@ void CodeGenRegBank::inferMatchingSuperRegClass(
// Topological shortcut: SubRC members have the wrong shape.
if (!TopoSigs.anyCommon(SubRC.getTopoSigs()))
continue;
// Compute the subset of RC that maps into SubRC.
// Compute the subset of RC that maps into SubRC with a single linear scan
// through SubToSuperRegs and the members of SubRC.
CodeGenRegister::Vec SubSetVec;
for (const CodeGenRegister *R : SubRC.getMembers()) {
auto It = SubToSuperRegs.find(R);
if (It != SubToSuperRegs.end()) {
const std::vector<const CodeGenRegister *> &SuperRegs = It->second;
SubSetVec.insert(SubSetVec.end(), SuperRegs.begin(), SuperRegs.end());
}
auto SubI = SubRC.getMembers().begin(), SubE = SubRC.getMembers().end();
for (auto &[Sub, Super] : SubToSuperRegs) {
while (SubI != SubE && **SubI < *Sub)
++SubI;
if (SubI == SubE)
break;
if (**SubI == *Sub)
SubSetVec.push_back(Super);
}

if (SubSetVec.empty())
Expand Down