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[TableGen][DecoderEmitter] Merge OPC_Decode with OPC_TryDecode #159178

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Merged
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Sep 16, 2025
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[TableGen][DecoderEmitter] Merge OPC_Decode with OPC_TryDecode #159178

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ae7973a
[TableGen][DecoderEmitter] Merge OPC_Decode with OPC_TryDecode
s-barannikov Sep 16, 2025
fbe09a9
update tests
s-barannikov Sep 16, 2025
eb3316e
Formatting
s-barannikov Sep 16, 2025
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1 change: 0 additions & 1 deletion llvm/include/llvm/MC/MCDecoderOps.h
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Expand Up @@ -24,7 +24,6 @@ enum DecoderOps {
// uleb128 Val)
OPC_CheckPredicate, // OPC_CheckPredicate(uleb128 PIdx)
OPC_Decode, // OPC_Decode(uleb128 Opcode, uleb128 DIdx)
OPC_TryDecode, // OPC_TryDecode(uleb128 Opcode, uleb128 DIdx)
OPC_SoftFail, // OPC_SoftFail(uleb128 PMask, uleb128 NMask)
};

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8 changes: 4 additions & 4 deletions llvm/test/TableGen/DecoderEmitter/additional-encoding.td
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Expand Up @@ -35,22 +35,22 @@ class I<dag out_ops, dag in_ops> : Instruction {
// CHECK-NEXT: /* 7 */ OPC_Scope, 8, 0, // end scope at 18
// CHECK-NEXT: /* 10 */ OPC_CheckField, 6, 6, 0, // if Inst{11-6} != 0x0
// CHECK-NEXT: /* 14 */ OPC_Decode, {{[0-9]+}}, 2, 0, // Opcode: {{.*}}:NOP, DecodeIdx: 0
// CHECK-NEXT: /* 18 */ OPC_TryDecode, {{[0-9]+}}, 2, 1, // Opcode: SHIFT0, DecodeIdx: 1
// CHECK-NEXT: /* 18 */ OPC_Decode, {{[0-9]+}}, 2, 1, // Opcode: SHIFT0, DecodeIdx: 1
// CHECK-NEXT: /* 22 */ OPC_FilterValueOrSkip, 1, 15, 0, // if Field != 0x1 skip to 41
// CHECK-NEXT: /* 26 */ OPC_Scope, 8, 0, // end scope at 37
// CHECK-NEXT: /* 29 */ OPC_CheckField, 6, 6, 0, // if Inst{11-6} != 0x0
// CHECK-NEXT: /* 33 */ OPC_Decode, {{[0-9]+}}, 2, 0, // Opcode: {{.*}}:NOP, DecodeIdx: 0
// CHECK-NEXT: /* 37 */ OPC_TryDecode, {{[0-9]+}}, 2, 1, // Opcode: SHIFT1, DecodeIdx: 1
// CHECK-NEXT: /* 37 */ OPC_Decode, {{[0-9]+}}, 2, 1, // Opcode: SHIFT1, DecodeIdx: 1
// CHECK-NEXT: /* 41 */ OPC_FilterValueOrSkip, 2, 15, 0, // if Field != 0x2 skip to 60
// CHECK-NEXT: /* 45 */ OPC_Scope, 8, 0, // end scope at 56
// CHECK-NEXT: /* 48 */ OPC_CheckField, 6, 6, 0, // if Inst{11-6} != 0x0
// CHECK-NEXT: /* 52 */ OPC_Decode, {{[0-9]+}}, 2, 0, // Opcode: {{.*}}:NOP, DecodeIdx: 0
// CHECK-NEXT: /* 56 */ OPC_TryDecode, {{[0-9]+}}, 2, 1, // Opcode: SHIFT2, DecodeIdx: 1
// CHECK-NEXT: /* 56 */ OPC_Decode, {{[0-9]+}}, 2, 1, // Opcode: SHIFT2, DecodeIdx: 1
// CHECK-NEXT: /* 60 */ OPC_FilterValue, 3, // if Field != 0x3
// CHECK-NEXT: /* 62 */ OPC_Scope, 8, 0, // end scope at 73
// CHECK-NEXT: /* 65 */ OPC_CheckField, 6, 6, 0, // if Inst{11-6} != 0x0
// CHECK-NEXT: /* 69 */ OPC_Decode, {{[0-9]+}}, 2, 0, // Opcode: {{.*}}:NOP, DecodeIdx: 0
// CHECK-NEXT: /* 73 */ OPC_TryDecode, {{[0-9]+}}, 2, 1, // Opcode: SHIFT3, DecodeIdx: 1
// CHECK-NEXT: /* 73 */ OPC_Decode, {{[0-9]+}}, 2, 1, // Opcode: SHIFT3, DecodeIdx: 1


class SHIFT<bits<2> opc> : I<(outs), (ins ShAmtOp:$shamt)>, EncSHIFT<opc>;
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4 changes: 2 additions & 2 deletions llvm/test/TableGen/DecoderEmitter/trydecode-emission.td
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Expand Up @@ -37,7 +37,7 @@ def InstB : TestInstruction {
// CHECK: /* 0 */ OPC_CheckField, 4, 4, 0, // if Inst{7-4} != 0x0
// CHECK-NEXT: /* 4 */ OPC_Scope, 8, 0, // end scope at 15
// CHECK-NEXT: /* 7 */ OPC_CheckField, 2, 2, 0, // if Inst{3-2} != 0x0
// CHECK-NEXT: /* 11 */ OPC_TryDecode, {{[0-9]+}}, {{[0-9]+}}, 0, // Opcode: InstB, DecodeIdx: 0
// CHECK-NEXT: /* 11 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 0, // Opcode: InstB, DecodeIdx: 0
// CHECK-NEXT: /* 15 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 1, // Opcode: InstA, DecodeIdx: 1
// CHECK-NEXT: };

Expand All @@ -50,7 +50,7 @@ def InstB : TestInstruction {
// CHECK-LARGE: /* 0 */ OPC_CheckField, 4, 4, 0, // if Inst{7-4} != 0x0
// CHECK-LARGE-NEXT: /* 4 */ OPC_Scope, 8, 0, 0, // end scope at 16
// CHECK-LARGE-NEXT: /* 8 */ OPC_CheckField, 2, 2, 0, // if Inst{3-2} != 0x0
// CHECK-LARGE-NEXT: /* 12 */ OPC_TryDecode, {{[0-9]+}}, {{[0-9]+}}, 0, // Opcode: InstB, DecodeIdx: 0
// CHECK-LARGE-NEXT: /* 12 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 0, // Opcode: InstB, DecodeIdx: 0
// CHECK-LARGE-NEXT: /* 16 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 1, // Opcode: InstA, DecodeIdx: 1
// CHECK-LARGE-NEXT: };

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8 changes: 4 additions & 4 deletions llvm/test/TableGen/DecoderEmitter/trydecode-emission2.td
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Expand Up @@ -35,9 +35,9 @@ def InstB : TestInstruction {
// CHECK-NEXT: /* 4 */ OPC_CheckField, 5, 3, 0,
// CHECK-NEXT: /* 8 */ OPC_Scope, 8, 0, // end scope at 19
// CHECK-NEXT: /* 11 */ OPC_CheckField, 0, 2, 3,
// CHECK-NEXT: /* 15 */ OPC_TryDecode, {{[0-9]+}}, {{[0-9]+}}, 0,
// CHECK-NEXT: /* 15 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 0,
// CHECK-NEXT: /* 19 */ OPC_CheckField, 3, 2, 0,
// CHECK-NEXT: /* 23 */ OPC_TryDecode, {{[0-9]+}}, {{[0-9]+}}, 1,
// CHECK-NEXT: /* 23 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 1,

// CHECK: if (!Check(S, DecodeInstB(MI, insn, Address, Decoder))) { DecodeComplete = false; return MCDisassembler::Fail; }
// CHECK: if (!Check(S, DecodeInstA(MI, insn, Address, Decoder))) { DecodeComplete = false; return MCDisassembler::Fail; }
Expand All @@ -46,9 +46,9 @@ def InstB : TestInstruction {
// CHECK-LARGE-NEXT: /* 4 */ OPC_CheckField, 5, 3, 0,
// CHECK-LARGE-NEXT: /* 8 */ OPC_Scope, 8, 0, 0, // end scope at 20
// CHECK-LARGE-NEXT: /* 12 */ OPC_CheckField, 0, 2, 3,
// CHECK-LARGE-NEXT: /* 16 */ OPC_TryDecode, {{[0-9]+}}, {{[0-9]+}}, 0,
// CHECK-LARGE-NEXT: /* 16 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 0,
// CHECK-LARGE-NEXT: /* 20 */ OPC_CheckField, 3, 2, 0,
// CHECK-LARGE-NEXT: /* 24 */ OPC_TryDecode, {{[0-9]+}}, {{[0-9]+}}, 1,
// CHECK-LARGE-NEXT: /* 24 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 1,
// CHECK-LARGE-NEXT: };

// CHECK-LARGE: if (!Check(S, DecodeInstB(MI, insn, Address, Decoder))) { DecodeComplete = false; return MCDisassembler::Fail; }
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4 changes: 2 additions & 2 deletions llvm/test/TableGen/DecoderEmitter/trydecode-emission3.td
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Expand Up @@ -38,7 +38,7 @@ def InstB : TestInstruction {
// CHECK: /* 0 */ OPC_CheckField, 4, 4, 0,
// CHECK-NEXT: /* 4 */ OPC_Scope, 8, 0, // end scope at 15
// CHECK-NEXT: /* 7 */ OPC_CheckField, 2, 2, 0,
// CHECK-NEXT: /* 11 */ OPC_TryDecode, {{[0-9]+}}, {{[0-9]+}}, 0,
// CHECK-NEXT: /* 11 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 0,
// CHECK-NEXT: /* 15 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 1, // Opcode: InstA, DecodeIdx: 1
// CHECK-NEXT: };

Expand All @@ -47,7 +47,7 @@ def InstB : TestInstruction {
// CHECK-LARGE: /* 0 */ OPC_CheckField, 4, 4, 0,
// CHECK-LARGE-NEXT: /* 4 */ OPC_Scope, 8, 0, 0, // end scope at 16
// CHECK-LARGE-NEXT: /* 8 */ OPC_CheckField, 2, 2, 0,
// CHECK-LARGE-NEXT: /* 12 */ OPC_TryDecode, {{[0-9]+}}, {{[0-9]+}}, 0,
// CHECK-LARGE-NEXT: /* 12 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 0,
// CHECK-LARGE-NEXT: /* 16 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 1, // Opcode: InstA, DecodeIdx: 1
// CHECK-LARGE-NEXT: };

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4 changes: 2 additions & 2 deletions llvm/test/TableGen/DecoderEmitter/trydecode-emission4.td
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Expand Up @@ -36,7 +36,7 @@ def InstB : TestInstruction {
// CHECK: /* 0 */ OPC_CheckField, 250, 3, 4, 0,
// CHECK-NEXT: /* 5 */ OPC_Scope, 9, 0, // end scope at 17
// CHECK-NEXT: /* 8 */ OPC_CheckField, 248, 3, 2, 0,
// CHECK-NEXT: /* 13 */ OPC_TryDecode, {{[0-9]+}}, {{[0-9]+}}, 0,
// CHECK-NEXT: /* 13 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 0,
// CHECK-NEXT: /* 17 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 1, // Opcode: InstA, DecodeIdx: 1
// CHECK-NEXT: };

Expand All @@ -46,7 +46,7 @@ def InstB : TestInstruction {
// CHECK-LARGE: /* 0 */ OPC_CheckField, 250, 3, 4, 0,
// CHECK-LARGE-NEXT: /* 5 */ OPC_Scope, 9, 0, 0, // end scope at 18
// CHECK-LARGE-NEXT: /* 9 */ OPC_CheckField, 248, 3, 2, 0,
// CHECK-LARGE-NEXT: /* 14 */ OPC_TryDecode, {{[0-9]+}}, {{[0-9]+}}, 0,
// CHECK-LARGE-NEXT: /* 14 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 0,
// CHECK-LARGE-NEXT: /* 18 */ OPC_Decode, {{[0-9]+}}, {{[0-9]+}}, 1, // Opcode: InstA, DecodeIdx: 1
// CHECK-LARGE-NEXT: };

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53 changes: 9 additions & 44 deletions llvm/utils/TableGen/DecoderEmitter.cpp
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Expand Up @@ -228,7 +228,6 @@ struct DecoderTableInfo {
DecoderSet Decoders;
bool HasCheckPredicate;
bool HasSoftFail;
bool HasTryDecode;

void insertPredicate(StringRef Predicate) {
Predicates.insert(CachedHashString(Predicate));
Expand Down Expand Up @@ -624,7 +623,6 @@ static StringRef getDecoderOpName(DecoderOps Op) {
CASE(OPC_CheckField);
CASE(OPC_CheckPredicate);
CASE(OPC_Decode);
CASE(OPC_TryDecode);
CASE(OPC_SoftFail);
}
#undef CASE
Expand Down Expand Up @@ -792,8 +790,7 @@ void DecoderEmitter::emitTable(formatted_raw_ostream &OS,
OS << "if !checkPredicate(" << PIdx << ") pop scope";
break;
}
case OPC_Decode:
case OPC_TryDecode: {
case OPC_Decode: {
// Decode the Opcode value.
unsigned Opc = DecodeAndEmitULEB128(I, OS);

Expand Down Expand Up @@ -1164,22 +1161,10 @@ void DecoderTableBuilder::emitSingletonTableEntry(
TableInfo.insertDecoder(Decoder);
unsigned DecoderIndex = TableInfo.getDecoderIndex(Decoder);

// Produce OPC_Decode or OPC_TryDecode opcode based on the information
// whether the instruction decoder is complete or not. If it is complete
// then it handles all possible values of remaining variable/unfiltered bits
// and for any value can determine if the bitpattern is a valid instruction
// or not. This means OPC_Decode will be the final step in the decoding
// process. If it is not complete, then the Fail return code from the
// decoder method indicates that additional processing should be done to see
// if there is any other instruction that also matches the bitpattern and
// can decode it.
const DecoderOps DecoderOp =
Encoding.hasCompleteDecoder() ? OPC_Decode : OPC_TryDecode;
TableInfo.Table.insertOpcode(DecoderOp);
TableInfo.Table.insertOpcode(MCD::OPC_Decode);
const Record *InstDef = Encodings[EncodingID].getInstruction()->TheDef;
TableInfo.Table.insertULEB128(Target.getInstrIntValue(InstDef));
TableInfo.Table.insertULEB128(DecoderIndex);
TableInfo.HasTryDecode |= DecoderOp == OPC_TryDecode;
}

std::unique_ptr<Filter>
Expand Down Expand Up @@ -1689,48 +1674,28 @@ static DecodeStatus decodeInstruction(const uint8_t DecodeTable[], MCInst &MI,
<< " makeUp(insn, Len);";
}
OS << R"(
S = decodeToMCInst(DecodeIdx, S, insn, MI, Address, DisAsm, DecodeComplete);
assert(DecodeComplete);

S = decodeToMCInst(DecodeIdx, S, insn, MI, Address, DisAsm,
DecodeComplete);
LLVM_DEBUG(dbgs() << Loc << ": OPC_Decode: opcode " << Opc
<< ", using decoder " << DecodeIdx << ": "
<< (S != MCDisassembler::Fail ? "PASS\n" : "FAIL\n"));
return S;
})";
if (TableInfo.HasTryDecode) {
OS << R"(
case OPC_TryDecode: {
// Decode the Opcode value.
unsigned Opc = decodeULEB128AndIncUnsafe(Ptr);
unsigned DecodeIdx = decodeULEB128AndIncUnsafe(Ptr);

// Perform the decode operation.
MCInst TmpMI;
TmpMI.setOpcode(Opc);
bool DecodeComplete;
S = decodeToMCInst(DecodeIdx, S, insn, TmpMI, Address, DisAsm, DecodeComplete);
LLVM_DEBUG(dbgs() << Loc << ": OPC_TryDecode: opcode " << Opc
<< ", using decoder " << DecodeIdx << ": ");
<< ", using decoder " << DecodeIdx << ": "
<< (S ? "PASS, " : "FAIL, "));

if (DecodeComplete) {
// Decoding complete.
LLVM_DEBUG(dbgs() << (S != MCDisassembler::Fail ? "PASS\n" : "FAIL\n"));
MI = TmpMI;
LLVM_DEBUG(dbgs() << "decoding complete\n");
return S;
}
assert(S == MCDisassembler::Fail);
if (ScopeStack.empty()) {
LLVM_DEBUG(dbgs() << "FAIL, returning FAIL\n");
LLVM_DEBUG(dbgs() << "returning Fail\n");
return MCDisassembler::Fail;
}
Ptr = ScopeStack.pop_back_val();
LLVM_DEBUG(dbgs() << "FAIL, continuing at " << Ptr - DecodeTable << '\n');
LLVM_DEBUG(dbgs() << "continuing at " << Ptr - DecodeTable << '\n');
// Reset decode status. This also drops a SoftFail status that could be
// set before the decode attempt.
S = MCDisassembler::Success;
break;
})";
}
if (TableInfo.HasSoftFail) {
OS << R"(
case OPC_SoftFail: {
Expand Down