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[TableGen][DecoderEmitter] Remove no longer needed MaxFilterWidth (NFC) #155382

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Merged
merged 1 commit into from
Aug 26, 2025
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[TableGen][DecoderEmitter] Remove no longer needed MaxFilterWidth (NFC) #155382

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21 changes: 4 additions & 17 deletions llvm/utils/TableGen/DecoderEmitter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -483,12 +483,6 @@ class FilterChooser {
// Links to the FilterChooser above us in the decoding tree.
const FilterChooser *Parent;

/// Some targets (ARM) specify more encoding bits in Inst that Size allows.
/// This field allows us to ignore the extra bits.
unsigned MaxFilterWidth;

const CodeGenTarget &Target;

/// If the selected filter matches multiple encodings, then this is the
/// starting position and the width of the filtered range.
unsigned StartBit;
Expand Down Expand Up @@ -522,16 +516,12 @@ class FilterChooser {
public:
/// Constructs a top-level filter chooser.
FilterChooser(ArrayRef<InstructionEncoding> Encodings,
ArrayRef<unsigned> EncodingIDs, unsigned MaxFilterWidth,
const CodeGenTarget &Target)
: Encodings(Encodings), EncodingIDs(EncodingIDs), Parent(nullptr),
MaxFilterWidth(MaxFilterWidth), Target(Target) {
ArrayRef<unsigned> EncodingIDs)
: Encodings(Encodings), EncodingIDs(EncodingIDs), Parent(nullptr) {
// Sort encoding IDs once.
stable_sort(this->EncodingIDs, LessEncodingIDByWidth(Encodings));
// Filter width is the width of the smallest encoding.
unsigned FilterWidth = Encodings[this->EncodingIDs.front()].getBitWidth();
// Cap it as necessary.
FilterWidth = std::min(FilterWidth, MaxFilterWidth);
FilterBits = KnownBits(FilterWidth);
doFilter();
}
Expand All @@ -540,15 +530,12 @@ class FilterChooser {
FilterChooser(ArrayRef<InstructionEncoding> Encodings,
ArrayRef<unsigned> EncodingIDs, const KnownBits &FilterBits,
const FilterChooser &Parent)
: Encodings(Encodings), EncodingIDs(EncodingIDs), Parent(&Parent),
MaxFilterWidth(Parent.MaxFilterWidth), Target(Parent.Target) {
: Encodings(Encodings), EncodingIDs(EncodingIDs), Parent(&Parent) {
// Inferior filter choosers are created from sorted array of encoding IDs.
assert(is_sorted(EncodingIDs, LessEncodingIDByWidth(Encodings)));
assert(!FilterBits.hasConflict() && "Broken filter");
// Filter width is the width of the smallest encoding.
unsigned FilterWidth = Encodings[EncodingIDs.front()].getBitWidth();
// Cap it as necessary.
FilterWidth = std::min(FilterWidth, MaxFilterWidth);
this->FilterBits = FilterBits.anyext(FilterWidth);
doFilter();
}
Expand Down Expand Up @@ -2562,7 +2549,7 @@ namespace {
auto [DecoderNamespace, HwModeID, Size] = Key;
const unsigned BitWidth = IsVarLenInst ? MaxInstLen : 8 * Size;
// Emit the decoder for this (namespace, hwmode, width) combination.
FilterChooser FC(Encodings, EncodingIDs, BitWidth, Target);
FilterChooser FC(Encodings, EncodingIDs);

// The decode table is cleared for each top level decoder function. The
// predicates and decoders themselves, however, are shared across all
Expand Down