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[TableGen] Use llvm::enumerate in one place (NFC) #136399

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Apr 19, 2025
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[TableGen] Use llvm::enumerate in one place (NFC) #136399

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24 changes: 11 additions & 13 deletions llvm/utils/TableGen/Common/CodeGenInstAlias.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -200,26 +200,24 @@ CodeGenInstAlias::CodeGenInstAlias(const Record *R, const CodeGenTarget &T)

// Decode and validate the arguments of the result.
unsigned AliasOpNo = 0;
for (unsigned i = 0, e = ResultInst->Operands.size(); i != e; ++i) {

for (auto [OpIdx, OpInfo] : enumerate(ResultInst->Operands)) {
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@kazutakahirata kazutakahirata Apr 19, 2025

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Could we use const auto &[OpIdx, OpInfo] here to avoid making a copy?

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@s-barannikov s-barannikov Apr 19, 2025 •
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If you're concerned about copying OpInfo, then there is no copy, AFAICT.
static_assert(std::is_reference_v<decltype(OpInfo)>); doesn't trigger.
I never learned how structured bindings exactly work, but it must be something with the fact that & applies to the structure itself and not to its elements.

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@s-barannikov s-barannikov Apr 19, 2025

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FWIW the size of the structure appears to be just 16 bytes.
image

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@kuhar kuhar Apr 19, 2025

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There is no copying here. This style is used all over mlir with enumerate.

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@kuhar kuhar Apr 19, 2025

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See https://llvm.org/docs/ProgrammersManual.html#iterating-over-ranges

// Tied registers don't have an entry in the result dag unless they're part
// of a complex operand, in which case we include them anyways, as we
// don't have any other way to specify the whole operand.
if (ResultInst->Operands[i].MINumOperands == 1 &&
ResultInst->Operands[i].getTiedRegister() != -1) {
if (OpInfo.MINumOperands == 1 && OpInfo.getTiedRegister() != -1) {
// Tied operands of different RegisterClass should be explicit within an
// instruction's syntax and so cannot be skipped.
int TiedOpNum = ResultInst->Operands[i].getTiedRegister();
if (ResultInst->Operands[i].Rec->getName() ==
int TiedOpNum = OpInfo.getTiedRegister();
if (OpInfo.Rec->getName() ==
ResultInst->Operands[TiedOpNum].Rec->getName())
continue;
}

if (AliasOpNo >= Result->getNumArgs())
PrintFatalError(R->getLoc(), "not enough arguments for instruction!");

const Record *InstOpRec = ResultInst->Operands[i].Rec;
unsigned NumSubOps = ResultInst->Operands[i].MINumOperands;
const Record *InstOpRec = OpInfo.Rec;
unsigned NumSubOps = OpInfo.MINumOperands;
ResultOperand ResOp(static_cast<int64_t>(0));
if (tryAliasOpMatch(Result, AliasOpNo, InstOpRec, (NumSubOps > 1),
R->getLoc(), T, ResOp)) {
Expand All @@ -229,12 +227,12 @@ CodeGenInstAlias::CodeGenInstAlias(const Record *R, const CodeGenTarget &T)
InstOpRec->getValueAsDef("ParserMatchClass")
->getValueAsString("Name") != "Imm")) {
ResultOperands.push_back(std::move(ResOp));
ResultInstOperandIndex.emplace_back(i, -1);
ResultInstOperandIndex.emplace_back(OpIdx, -1);
++AliasOpNo;

// Otherwise, we need to match each of the suboperands individually.
} else {
const DagInit *MIOI = ResultInst->Operands[i].MIOperandInfo;
const DagInit *MIOI = OpInfo.MIOperandInfo;
for (unsigned SubOp = 0; SubOp != NumSubOps; ++SubOp) {
const Record *SubRec = cast<DefInit>(MIOI->getArg(SubOp))->getDef();

Expand All @@ -244,7 +242,7 @@ CodeGenInstAlias::CodeGenInstAlias(const Record *R, const CodeGenTarget &T)
Result->getArgName(AliasOpNo)->getAsUnquotedString() + "." +
MIOI->getArgName(SubOp)->getAsUnquotedString(),
SubRec);
ResultInstOperandIndex.emplace_back(i, SubOp);
ResultInstOperandIndex.emplace_back(OpIdx, SubOp);
}
++AliasOpNo;
}
Expand All @@ -254,15 +252,15 @@ CodeGenInstAlias::CodeGenInstAlias(const Record *R, const CodeGenTarget &T)
// If the argument did not match the instruction operand, and the operand
// is composed of multiple suboperands, try matching the suboperands.
if (NumSubOps > 1) {
const DagInit *MIOI = ResultInst->Operands[i].MIOperandInfo;
const DagInit *MIOI = OpInfo.MIOperandInfo;
for (unsigned SubOp = 0; SubOp != NumSubOps; ++SubOp) {
if (AliasOpNo >= Result->getNumArgs())
PrintFatalError(R->getLoc(), "not enough arguments for instruction!");
const Record *SubRec = cast<DefInit>(MIOI->getArg(SubOp))->getDef();
if (tryAliasOpMatch(Result, AliasOpNo, SubRec, false, R->getLoc(), T,
ResOp)) {
ResultOperands.push_back(ResOp);
ResultInstOperandIndex.emplace_back(i, SubOp);
ResultInstOperandIndex.emplace_back(OpIdx, SubOp);
++AliasOpNo;
} else {
PrintFatalError(
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