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[TableGen][DecoderEmitter] Add extractBits() overloads #159405

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[TableGen][DecoderEmitter] Add extractBits() overloads #159405

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19 changes: 19 additions & 0 deletions llvm/include/llvm/MC/MCDecoder.h
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@
#ifndef LLVM_MC_MCDECODER_H
#define LLVM_MC_MCDECODER_H

#include "llvm/ADT/APInt.h"
#include "llvm/MC/MCDisassembler/MCDisassembler.h"
#include "llvm/Support/MathExtras.h"
#include <bitset>
Expand Down Expand Up @@ -58,6 +59,24 @@ uint64_t fieldFromInstruction(const std::bitset<N> &Insn, unsigned StartBit,
return ((Insn >> StartBit) & Mask).to_ullong();
}

template <unsigned StartBit, unsigned NumBits, typename T>
inline std::enable_if_t<std::is_unsigned_v<T>, T> extractBits(T Val) {
static_assert(StartBit + NumBits <= std::numeric_limits<T>::digits);
return (Val >> StartBit) & maskTrailingOnes<T>(NumBits);
}

template <unsigned StartBit, unsigned NumBits, size_t N>
uint64_t extractBits(const std::bitset<N> &Val) {
static_assert(StartBit + NumBits <= N);
std::bitset<N> Mask = maskTrailingOnes<uint64_t>(NumBits);
return ((Val >> StartBit) & Mask).to_ullong();
}

template <unsigned StartBit, unsigned NumBits>
uint64_t extractBits(const APInt &Val) {
return Val.extractBitsAsZExtValue(NumBits, StartBit);
}

} // namespace llvm::MCD

#endif // LLVM_MC_MCDECODER_H
7 changes: 3 additions & 4 deletions llvm/utils/TableGen/DecoderEmitter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1031,8 +1031,7 @@ static void emitBinaryParser(raw_ostream &OS, indent Indent,
// One variable part and no/zero constant part. Initialize `tmp` with the
// variable part.
auto [Base, Width, Offset] = OpInfo.fields().front();
OS << Indent << "tmp = fieldFromInstruction(insn, " << Base << ", " << Width
<< ')';
OS << Indent << "tmp = extractBits<" << Base << ", " << Width << ">(insn)";
if (Offset)
OS << " << " << Offset;
OS << ";\n";
Expand All @@ -1042,8 +1041,8 @@ static void emitBinaryParser(raw_ostream &OS, indent Indent,
OS << Indent << "tmp = " << format_hex(OpInfo.InitValue.value_or(0), 0)
<< ";\n";
for (auto [Base, Width, Offset] : OpInfo.fields()) {
OS << Indent << "tmp |= fieldFromInstruction(insn, " << Base << ", "
<< Width << ')';
OS << Indent << "tmp |= extractBits<" << Base << ", " << Width
<< ">(insn)";
if (Offset)
OS << " << " << Offset;
OS << ";\n";
Expand Down
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