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-rw-r--r--llvm/utils/TableGen/DecoderEmitter.cpp150
1 files changed, 52 insertions, 98 deletions
diff --git a/llvm/utils/TableGen/DecoderEmitter.cpp b/llvm/utils/TableGen/DecoderEmitter.cpp
index 6bcaf70..76dafca 100644
--- a/llvm/utils/TableGen/DecoderEmitter.cpp
+++ b/llvm/utils/TableGen/DecoderEmitter.cpp
@@ -490,6 +490,7 @@ class FilterChooser {
/// If the selected filter matches multiple encodings, and there is
/// *exactly one* encoding in which all bits are known in the filtered range,
/// then this is the ID of that encoding.
+ /// Also used when there is only one encoding.
std::optional<unsigned> SingletonEncodingID;
/// If the selected filter matches multiple encodings, and there is
@@ -591,13 +592,6 @@ private:
void emitSingletonTableEntry(DecoderTableInfo &TableInfo,
unsigned EncodingID) const;
- // Emits code to decode the singleton, and then to decode the rest.
- void emitSingletonTableEntry(DecoderTableInfo &TableInfo) const;
-
- // Emit table entries to decode instructions given a segment or segments of
- // bits.
- void emitTableEntry(DecoderTableInfo &TableInfo) const;
-
void emitBinaryParser(raw_ostream &OS, indent Indent,
const OperandInfo &OpInfo) const;
@@ -624,8 +618,7 @@ private:
void doFilter();
public:
- // emitTableEntries - Emit state machine entries to decode our share of
- // instructions.
+ /// Emits state machine entries to decode our share of instructions.
void emitTableEntries(DecoderTableInfo &TableInfo) const;
void dump() const;
@@ -700,70 +693,6 @@ void FilterChooser::applyFilter(const Filter &F) {
}
}
-// Emit table entries to decode instructions given a segment or segments
-// of bits.
-void FilterChooser::emitTableEntry(DecoderTableInfo &TableInfo) const {
- assert(isUInt<8>(NumBits) && "NumBits overflowed uint8 table entry!");
- TableInfo.Table.push_back(MCD::OPC_ExtractField);
-
- TableInfo.Table.insertULEB128(StartBit);
- TableInfo.Table.push_back(NumBits);
-
- // If VariableFC is present, we need to add a new scope for this filter.
- // Otherwise, we can skip adding a new scope and any patching added will
- // automatically be added to the enclosing scope.
- const uint64_t LastFilter = FilterChooserMap.rbegin()->first;
- if (VariableFC)
- TableInfo.FixupStack.emplace_back();
-
- DecoderTable &Table = TableInfo.Table;
-
- size_t PrevFilter = 0;
- for (const auto &[FilterVal, Delegate] : FilterChooserMap) {
- // The last filtervalue emitted can be OPC_FilterValue if we are at
- // outermost scope.
- const uint8_t DecoderOp =
- FilterVal == LastFilter && TableInfo.isOutermostScope()
- ? MCD::OPC_FilterValueOrFail
- : MCD::OPC_FilterValue;
- Table.push_back(DecoderOp);
- Table.insertULEB128(FilterVal);
- if (DecoderOp == MCD::OPC_FilterValue) {
- // Reserve space for the NumToSkip entry. We'll backpatch the value later.
- PrevFilter = Table.insertNumToSkip();
- } else {
- PrevFilter = 0;
- }
-
- // We arrive at a category of instructions with the same segment value.
- // Now delegate to the sub filter chooser for further decodings.
- // The case may fallthrough, which happens if the remaining well-known
- // encoding bits do not match exactly.
- Delegate->emitTableEntries(TableInfo);
-
- // Now that we've emitted the body of the handler, update the NumToSkip
- // of the filter itself to be able to skip forward when false.
- if (PrevFilter)
- Table.patchNumToSkip(PrevFilter, Table.size());
- }
-
- if (VariableFC) {
- // Each scope should always have at least one filter value to check for.
- assert(PrevFilter != 0 && "empty filter set!");
- TableInfo.popScope();
- PrevFilter = 0; // Don't re-process the filter's fallthrough.
-
- // Delegate to the sub filter chooser for further decoding.
- VariableFC->emitTableEntries(TableInfo);
- }
-
- // If there is no fallthrough and the final filter was not in the outermost
- // scope, then it must be fixed up according to the enclosing scope rather
- // than the current position.
- if (PrevFilter)
- TableInfo.FixupStack.back().push_back(PrevFilter);
-}
-
// Returns the number of fanout produced by the filter. More fanout implies
// the filter distinguishes more categories of instructions.
unsigned Filter::usefulness() const {
@@ -1425,17 +1354,6 @@ void FilterChooser::emitSingletonTableEntry(DecoderTableInfo &TableInfo,
}
}
-// Emits table entries to decode the singleton, and then to decode the rest.
-void FilterChooser::emitSingletonTableEntry(DecoderTableInfo &TableInfo) const {
- // complex singletons need predicate checks from the first singleton
- // to refer forward to the variable filterchooser that follows.
- TableInfo.pushScope();
- emitSingletonTableEntry(TableInfo, *SingletonEncodingID);
- TableInfo.popScope();
-
- VariableFC->emitTableEntries(TableInfo);
-}
-
// reportRegion is a helper function for filterProcessor to mark a region as
// eligible for use as a filter region.
void FilterChooser::reportRegion(std::vector<std::unique_ptr<Filter>> &Filters,
@@ -1694,8 +1612,10 @@ void FilterChooser::doFilter() {
assert(!EncodingIDs.empty() && "FilterChooser created with no instructions");
// No filter needed.
- if (EncodingIDs.size() < 2)
+ if (EncodingIDs.size() == 1) {
+ SingletonEncodingID = EncodingIDs.front();
return;
+ }
std::unique_ptr<Filter> BestFilter = findBestFilter();
if (BestFilter) {
@@ -1726,22 +1646,56 @@ void FilterChooser::dump() const {
}
}
-// emitTableEntries - Emit state machine entries to decode our share of
-// instructions.
void FilterChooser::emitTableEntries(DecoderTableInfo &TableInfo) const {
- if (EncodingIDs.size() == 1) {
- // There is only one instruction in the set, which is great!
- // Call emitSingletonDecoder() to see whether there are any remaining
- // encodings bits.
- emitSingletonTableEntry(TableInfo, EncodingIDs[0]);
- return;
+ // If there are other encodings that could match if those with all bits
+ // known don't, enter a scope so that they have a chance.
+ if (VariableFC)
+ TableInfo.pushScope();
+
+ if (SingletonEncodingID) {
+ assert(FilterChooserMap.empty());
+ // There is only one encoding in which all bits in the filtered range are
+ // fully defined, but we still need to check if the remaining (unfiltered)
+ // bits are valid for this encoding. We also need to check predicates etc.
+ emitSingletonTableEntry(TableInfo, *SingletonEncodingID);
+ } else {
+ // The general case: emit a switch over the field value.
+ DecoderTable &Table = TableInfo.Table;
+ Table.push_back(MCD::OPC_ExtractField);
+ Table.insertULEB128(StartBit);
+ assert(isUInt<8>(NumBits) && "NumBits overflowed uint8 table entry!");
+ Table.push_back(NumBits);
+
+ // Emit switch cases for all but the last element.
+ for (const auto &[FilterVal, Delegate] : drop_end(FilterChooserMap)) {
+ Table.push_back(MCD::OPC_FilterValue);
+ Table.insertULEB128(FilterVal);
+ size_t FixupPos = Table.insertNumToSkip();
+
+ // Emit table entries for this case.
+ Delegate->emitTableEntries(TableInfo);
+
+ // Patch the previous OPC_FilterValue to fall through to the next case.
+ Table.patchNumToSkip(FixupPos, Table.size());
+ }
+
+ // Emit a switch case for the last element. It never falls through;
+ // if it doesn't match, we leave the current scope.
+ const auto &[FilterVal, Delegate] = *FilterChooserMap.rbegin();
+ Table.push_back(!TableInfo.isOutermostScope() ? MCD::OPC_FilterValue
+ : MCD::OPC_FilterValueOrFail);
+ Table.insertULEB128(FilterVal);
+ if (!TableInfo.isOutermostScope())
+ TableInfo.FixupStack.back().push_back(Table.insertNumToSkip());
+
+ // Emit table entries for the last case.
+ Delegate->emitTableEntries(TableInfo);
}
- // Use the best filter to do the decoding!
- if (SingletonEncodingID)
- emitSingletonTableEntry(TableInfo);
- else
- emitTableEntry(TableInfo);
+ if (VariableFC) {
+ TableInfo.popScope();
+ VariableFC->emitTableEntries(TableInfo);
+ }
}
static std::string findOperandDecoderMethod(const Record *Record) {
generated by cgit v1.1 at 2025-09-30 07:59:30 +0000