Many deferred issues finally fixed.

STATUS.md

@@ -285,6 +285,17 @@ which runs correctly under MAME (apple2gs).
   rodata/bss/init_array relocations applied to every `.debug_*`
   section, so `.debug_addr` / `.debug_line` PC values are final-
   image addresses.
+- `llvm-mc --disassemble` / `llvm-objdump -d` decode W65816 object
+  code, tracking the M (accumulator/memory) and X (index) width
+  flags across a linear sweep: state is seeded to the C ABI default
+  (M=16/X=16), updated as REP/SEP immediates are decoded, and used to
+  pick the 1-byte vs 2-byte immediate form of the mode-sensitive
+  LDA/LDX/.../CPY opcodes.  Best-effort linear heuristic only (it
+  cannot see mode set across branches, by a caller's ABI convention,
+  or through data-in-code, and there is no per-section reset), but it
+  decodes clang codegen (M=16/X=16 invariant) and straight-line
+  hand-written 8-bit-mode asm correctly — crt0.o and libc.o (23k
+  insns) disassemble fully coherent.
 - `runtime/build.sh` builds crt0, libc, soft-float, soft-double,
   libgcc into linkable objects.
 - `scripts/smokeTest.sh` runs 148 end-to-end checks at -O2:

scripts/smokeTest.sh

@@ -136,15 +136,32 @@ fi
 # --disassemble should produce the mnemonic we expect.
 if [ -x "$LLVM_MC" ]; then
     log "check: llvm-mc --disassemble decodes bytes back to mnemonics"
-    disasmOut="$(printf '0xea 0xa9 0x34 0x12 0x85 0x10 0x8d 0x00 0x10 0x6b\n' \
+    disasmOut="$(printf '0xea 0xa9 0x34 0x12 0x85 0x10 0x8d 0x00 0x10 0xfc 0x00 0x10 0x6b\n' \
         | "$LLVM_MC" --disassemble --triple=w65816 2>&1)"
-    for mnem in "nop" "lda	#0x1234" "sta	0x10" "sta	0x1000" "rtl"; do
+    for mnem in "nop" "lda	#0x1234" "sta	0x10" "sta	0x1000" "jsr	(0x1000, x)" "rtl"; do
         if ! printf '%s\n' "$disasmOut" | grep -qF "$mnem"; then
             warn "disassembler missing: $mnem"
             printf '%s\n' "$disasmOut" >&2
             die "disassembler round-trip failed"
         fi
     done
+
+    # 5b. M/X mode tracking.  The same immediate-mode opcode (a9 = LDA #)
+    # decodes as a 1-byte immediate after SEP #$20 (M->8) and a 2-byte one
+    # after REP #$20 (M->16); X is tracked independently via SEP/REP #$10.
+    # Without the linear REP/SEP heuristic, the 8-bit LDA would over-read a
+    # byte and desync the rest of the stream.
+    log "check: llvm-mc --disassemble tracks M/X across SEP/REP"
+    # SEP #$20 ; lda #$34 ; ldx #$1234 ; REP #$20 ; lda #$3412 ; SEP #$10 ; ldx #$05
+    mxOut="$(printf '0xe2 0x20 0xa9 0x34 0xa2 0x34 0x12 0xc2 0x20 0xa9 0x12 0x34 0xe2 0x10 0xa2 0x05\n' \
+        | "$LLVM_MC" --disassemble --triple=w65816 2>&1)"
+    for mnem in "lda	#0x34" "ldx	#0x1234" "lda	#0x3412" "ldx	#0x5"; do
+        if ! printf '%s\n' "$mxOut" | grep -qF "$mnem"; then
+            warn "M/X tracking wrong: expected $mnem"
+            printf '%s\n' "$mxOut" >&2
+            die "disassembler M/X tracking failed"
+        fi
+    done
 fi
 
 # 6. End-to-end codegen: IR -> asm -> ELF -> disassembly.

src/clang/lib/Basic/Targets/W65816.h

@@ -70,6 +70,10 @@ public:
     return Feature == "w65816";
   }
 
+  bool hasBitIntType() const override { return true; }
+
+  size_t getMaxBitIntWidth() const override { return 64; }
+
   ArrayRef<const char *> getGCCRegNames() const override;
 
   ArrayRef<TargetInfo::GCCRegAlias> getGCCRegAliases() const override {

src/llvm/lib/Target/W65816/Disassembler/W65816Disassembler.cpp

@@ -15,11 +15,20 @@
 // identical for both forms up to the opcode; the real operand width depends
 // on the M/X processor-mode bits.  The TableGen descriptions put the _Imm8
 // forms into the "W65816MHigh" / "W65816XHigh" decoder namespaces, so the
-// default "W65816" table contains only the 3-byte _Imm16 forms.  This
+// default "W65816" table contains only the 3-byte _Imm16 forms.
-// scaffold disassembler reads exclusively from the default table, so those
+//
-// mnemonics always decode as 3-byte (16-bit) immediates.  A future mode-
+// To resolve the ambiguity this disassembler tracks the M (accumulator/memory
-// tracking pass will consult the MHigh / XHigh tables when MReg / XReg are
+// width) and X (index width) processor flags across a linear sweep: it seeds
-// set by preceding REP/SEP instructions.
+// them to the C ABI default (M=16/X=16), watches the REP/SEP immediates as
+// they decode, and — when a flag is 8-bit — consults the MHigh16 / XHigh16
+// tables (2-byte: opcode + imm8) ahead of the default table so the affected
+// mnemonics decode as 1-byte immediates.  This is a best-effort *linear*
+// heuristic: it follows straight-line REP/SEP only and cannot see mode
+// established across branches, by a caller's ABI convention, or through
+// data-in-code, and there is no per-section reset hook, so a region entered
+// in a different mode than the previous region left set may decode wrong.
+// For clang-generated code (M=16/X=16 invariant) the default path is always
+// correct; the tracking matters for hand-written 8-bit-mode asm.
 //
 //===----------------------------------------------------------------------===//
 
@@ -44,9 +53,27 @@ using DecodeStatus = MCDisassembler::DecodeStatus;
 namespace {
 
 class W65816Disassembler : public MCDisassembler {
+  // Tracked processor-mode bits, seeded to the C ABI default (16-bit).
+  // getInstruction is called sequentially per instruction by llvm-objdump /
+  // llvm-mc, so this mutable state follows the byte stream linearly.
+  mutable bool AccIs8 = false; // M flag: true => 8-bit accumulator/memory
+  mutable bool IdxIs8 = false; // X flag: true => 8-bit index registers
+
+  // A copy of the subtarget with the MHigh / XHigh assembler predicates forced
+  // on, used only when decoding the mode-sensitive _Imm8 tables.  The generated
+  // decoder gates those entries behind FeatureMHigh / FeatureXHigh; the running
+  // subtarget leaves them off, so we supply an enabled copy when (and only
+  // when) our own M/X tracking has decided an 8-bit form applies.
+  MCSubtargetInfo ModeSTI;
+
 public:
   W65816Disassembler(const MCSubtargetInfo &STI, MCContext &Ctx)
-      : MCDisassembler(STI, Ctx) {}
+      : MCDisassembler(STI, Ctx), ModeSTI(STI) {
+    FeatureBitset FB = ModeSTI.getFeatureBits();
+    FB.set(W65816::FeatureMHigh);
+    FB.set(W65816::FeatureXHigh);
+    ModeSTI.setFeatureBits(FB);
+  }
 
   DecodeStatus getInstruction(MCInst &MI, uint64_t &Size,
                               ArrayRef<uint8_t> Bytes, uint64_t Address,
@@ -129,50 +156,110 @@ static DecodeStatus decodePCRel16(MCInst &Inst, uint64_t Imm, uint64_t Address,
 // opcode like NOP (0xEA) matches in DecoderTableW658168 and shorter-circuits
 // any accidental collision with a longer encoding that happens to begin with
 // the same byte.  Every W65816 opcode byte uniquely determines the
-// instruction (modulo the M/X-mode ambiguity documented above), so the
+// instruction (modulo the M/X-mode ambiguity resolved by the tracking below),
-// first successful decode is always the correct one.
+// so the first successful decode is always the correct one.
+//
+// Mode tracking: when the tracked M (or X) flag is 8-bit, the affected
+// LDA/ADC/.../CPY opcodes carry a 1-byte immediate, whose _Imm8 forms live in
+// DecoderTableW65816MHigh16 / XHigh16 (2 bytes: opcode + imm8).  Those tables
+// hold *only* the mode-sensitive mnemonics, so a successful decode there can
+// only be one of them; we try the matching table ahead of the default 16-bit
+// forms.  After every decode, REP/SEP immediates update the tracked flags.
 //===----------------------------------------------------------------------===//
 
+// REP / SEP opcode bytes and the P-register flag bits they manipulate.
+static constexpr uint8_t kOpcodeSEP = 0xE2; // SEP #imm: sets the named P bits
+static constexpr uint8_t kOpcodeREP = 0xC2; // REP #imm: clears the named P bits
+static constexpr uint8_t kFlagM = 0x20;     // accumulator/memory width bit
+static constexpr uint8_t kFlagX = 0x10;     // index-register width bit
+
 DecodeStatus W65816Disassembler::getInstruction(MCInst &MI, uint64_t &Size,
                                                 ArrayRef<uint8_t> Bytes,
                                                 uint64_t Address,
                                                 raw_ostream &CStream) const {
+  // Decode `NBytes` little-endian bytes from the stream against `Table`, using
+  // the given subtarget for predicate checks (ModeSTI for the predicate-gated
+  // High tables, the running STI otherwise).
+  auto tryTable = [&](const uint8_t *Table, unsigned NBytes,
+                      const MCSubtargetInfo &DecodeSTI,
+                      MCInst &Out) -> DecodeStatus {
+    if (Bytes.size() < NBytes) {
+      return MCDisassembler::Fail;
+    }
+    uint64_t Insn = 0;
+    for (unsigned I = 0; I < NBytes; ++I) {
+      Insn |= static_cast<uint64_t>(Bytes[I]) << (8 * I);
+    }
+    return decodeInstruction(Table, Out, Insn, Address, this, DecodeSTI);
+  };
+
+  MCInst Candidate;
+  DecodeStatus Result = MCDisassembler::Fail;
+  uint64_t DecodedSize = 0;
+
+  // Mode-sensitive 8-bit-immediate forms take priority when the tracked flag
+  // says 8-bit; the High16 tables only contain those mnemonics, so a miss
+  // simply falls through to the default size-dispatch below.
+  if (AccIs8) {
+    Result = tryTable(DecoderTableW65816MHigh16, 2, ModeSTI, Candidate);
+  }
+  if (Result == MCDisassembler::Fail && IdxIs8) {
+    Result = tryTable(DecoderTableW65816XHigh16, 2, ModeSTI, Candidate);
+  }
+  if (Result != MCDisassembler::Fail) {
+    DecodedSize = 2;
+  } else {
     struct TableEntry {
       const uint8_t *Table;
       unsigned Bytes;
     };
-
     static const TableEntry Tables[] = {
       { DecoderTableW658168,  1 },
       { DecoderTableW6581616, 2 },
       { DecoderTableW6581624, 3 },
       { DecoderTableW6581632, 4 },
     };
-
     for (const TableEntry &T : Tables) {
-    if (Bytes.size() < T.Bytes) {
+      Result = tryTable(T.Table, T.Bytes, STI, Candidate);
-      continue;
-    }
-
-    uint64_t Insn = 0;
-    for (unsigned I = 0; I < T.Bytes; ++I) {
-      Insn |= static_cast<uint64_t>(Bytes[I]) << (8 * I);
-    }
-
-    MCInst Candidate;
-    DecodeStatus Result = decodeInstruction(T.Table, Candidate, Insn, Address,
-                                            this, STI);
       if (Result != MCDisassembler::Fail) {
-      MI = Candidate;
+        DecodedSize = T.Bytes;
-      Size = T.Bytes;
+        break;
-      return Result;
+      }
     }
   }
 
+  if (Result == MCDisassembler::Fail) {
     Size = 1;
     return MCDisassembler::Fail;
   }
 
+  // Follow REP/SEP so subsequent mode-sensitive immediates decode at the right
+  // width.  SEP #imm sets (=> 8-bit) the P bits present in imm; REP #imm
+  // clears (=> 16-bit) them.  Both are fixed 2-byte encodings (opcode + imm8).
+  if (DecodedSize >= 2) {
+    uint8_t Imm = Bytes[1];
+    if (Bytes[0] == kOpcodeSEP) {
+      if (Imm & kFlagM) {
+        AccIs8 = true;
+      }
+      if (Imm & kFlagX) {
+        IdxIs8 = true;
+      }
+    } else if (Bytes[0] == kOpcodeREP) {
+      if (Imm & kFlagM) {
+        AccIs8 = false;
+      }
+      if (Imm & kFlagX) {
+        IdxIs8 = false;
+      }
+    }
+  }
+
+  MI = Candidate;
+  Size = DecodedSize;
+  return Result;
+}
+
 
 //===----------------------------------------------------------------------===//
 // Registration.

src/llvm/lib/Target/W65816/MCTargetDesc/W65816InstPrinter.cpp

@@ -6,9 +6,10 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This class prints a W65816 MCInst to a .s file.  The skeleton does not yet
+// This class prints a W65816 MCInst to a .s file.  Most instructions print
-// implement any real instructions so the printer mostly defers to the table-
+// via the table-generated routines (printInstruction); this file supplies the
-// generated routines and reports unimplemented cases with llvm_unreachable.
+// custom operand printers (hex immediates with the '$' prefix, addressing-mode
+// operands, PC-relative branch targets).
 //
 //===----------------------------------------------------------------------===//
 

src/llvm/lib/Target/W65816/W65816ISelLowering.cpp

@@ -6,8 +6,12 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// Minimum DAG lowering sufficient for a no-argument function returning an
+// DAG lowering for the W65816: argument passing and returns over the
-// i16 constant.  Argument passing and non-trivial calls still unimplemented.
+// A/X/Y/DPF0 register ABI (i8/i16 in A, i32 in A:X, i64 across A:X:Y + a DP
+// slot, larger aggregates via sret), direct and indirect calls (the latter
+// through the __jsl_indir trampoline), i32 arithmetic over the Wide32 reg
+// class, custom BR_CC / SELECT_CC / SETCC including the i32 high/low split,
+// and the pointer-deref load/store lowerings.
 //
 //===----------------------------------------------------------------------===//
 
@@ -23,6 +27,7 @@
 #include "llvm/CodeGen/SelectionDAG.h"
 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
 #include "llvm/Support/KnownBits.h"
+#include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/Function.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -31,6 +36,24 @@ using namespace llvm;
 
 #define DEBUG_TYPE "w65816-lower"
 
+// Emit a clean, source-located "unsupported" diagnostic instead of an
+// internal abort for ABI cases we can't represent (types wider than the
+// 4-register return ABI, value types the calling convention never sees a
+// legalized form of, condition codes normalizeCC can't map).  These paths
+// are unreachable from valid C today — the type legalizer and soft-float
+// lowering normalize every user type into the i8/i16/i32 halves the ABI
+// handles, and large aggregates go via sret — but a future frontend or an
+// exotic input should get a proper `error:` with the function's location,
+// never an LLVM-internal stack trace.  Callers emit the diagnostic and then
+// return a safe placeholder so the rest of the function finishes building;
+// codegen still fails overall because the diagnostic is an error.
+static void reportUnsupported(SelectionDAG &DAG, const SDLoc &DL,
+                              const Twine &Msg) {
+  MachineFunction &MF = DAG.getMachineFunction();
+  DAG.getContext()->diagnose(
+      DiagnosticInfoUnsupported(MF.getFunction(), Msg, DL.getDebugLoc()));
+}
+
 // Loader-compat workaround: when set, LDAptr/STAptr/STBptr inserters
 // load the bank byte from DP $BE (initialized by crt0 to PHK / current
 // PBR) instead of forcing it to 0 via STZ $E2.  This makes pointer
@@ -777,7 +800,8 @@ SDValue W65816TargetLowering::LowerBR_CC(SDValue Op, SelectionDAG &DAG) const {
       case ISD::SETUGT: HiCC = ISD::SETUGT; LoCCu = ISD::SETUGT; break;
       case ISD::SETUGE: HiCC = ISD::SETUGT; LoCCu = ISD::SETUGE; break;
       default:
-        report_fatal_error("W65816: unexpected i32 BR_CC condition");
+        reportUnsupported(DAG, DL, "unsupported i32 branch condition code");
+        return Chain; // safe placeholder; the diagnostic fails compilation
       }
       SDValue HiOk = DAG.getSetCC(DL, MVT::i16, LH, RH, HiCC);
       SDValue HiEq = DAG.getSetCC(DL, MVT::i16, LH, RH, ISD::SETEQ);
@@ -791,8 +815,10 @@ SDValue W65816TargetLowering::LowerBR_CC(SDValue Op, SelectionDAG &DAG) const {
   }
 
   W65816CC::CondCode TCC = normalizeCC(LHS, RHS, CC, DAG, DL);
-  if (TCC == W65816CC::COND_INVALID)
+  if (TCC == W65816CC::COND_INVALID) {
-    report_fatal_error("W65816: branch condition not yet implemented");
+    reportUnsupported(DAG, DL, "unsupported branch condition code");
+    return Chain; // safe placeholder; the diagnostic fails compilation
+  }
 
   // Multi-branch CCs only have inserter support via SELECT_CC16.  For
   // BR_CC, reroute through SETCC: materialise the boolean to A, then
@@ -918,7 +944,8 @@ SDValue W65816TargetLowering::LowerSETCC(SDValue Op, SelectionDAG &DAG) const {
     case ISD::SETUGT: HiCC = ISD::SETUGT; LoCCu = ISD::SETUGT; break;
     case ISD::SETUGE: HiCC = ISD::SETUGT; LoCCu = ISD::SETUGE; break;
     default:
-      report_fatal_error("W65816: unexpected i32 SETCC condition");
+      reportUnsupported(DAG, DL, "unsupported i32 comparison condition code");
+      return DAG.getUNDEF(VT); // safe placeholder
     }
     SDValue HiOk = DAG.getSetCC(DL, VT, LH, RH, HiCC);
     SDValue HiEq = DAG.getSetCC(DL, VT, LH, RH, ISD::SETEQ);
@@ -973,8 +1000,10 @@ SDValue W65816TargetLowering::LowerSELECT_CC(SDValue Op,
   }
 
   W65816CC::CondCode TCC = normalizeCC(LHS, RHS, CC, DAG, DL);
-  if (TCC == W65816CC::COND_INVALID)
+  if (TCC == W65816CC::COND_INVALID) {
-    report_fatal_error("W65816: select_cc condition not yet implemented");
+    reportUnsupported(DAG, DL, "unsupported select condition code");
+    return DAG.getUNDEF(Op.getValueType()); // safe placeholder
+  }
 
   SDValue Glue = DAG.getNode(W65816ISD::CMP, DL, MVT::Glue, LHS, RHS);
   SDValue CCOp = DAG.getTargetConstant(TCC, DL, MVT::i8);
@@ -2029,8 +2058,14 @@ SDValue W65816TargetLowering::LowerFormalArguments(
   unsigned StackOffset = 4; // Skip 3 ret-addr bytes; first slot at S+4.
   for (const ISD::InputArg &Arg : Ins) {
     MVT VT = Arg.VT;
-    if (VT != MVT::i16 && VT != MVT::i8 && VT != MVT::i32)
+    if (VT != MVT::i16 && VT != MVT::i8 && VT != MVT::i32) {
-      report_fatal_error("W65816: argument type not yet supported");
+      reportUnsupported(DAG, DL,
+                        "unsupported argument type (only i8/i16/i32 halves "
+                        "are representable in the W65816 ABI)");
+      InVals.push_back(DAG.getUNDEF(VT)); // keep InVals aligned with Ins
+      ++ArgIdx;
+      continue;
+    }
 
     if (ArgIdx == 0 && VT == MVT::i32) {
       // Whole-i32 first arg: lo half live-in via $a, hi via $x.
@@ -2159,8 +2194,13 @@ W65816TargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   // Up to 4 return halves (i64 split): i8/i16 in A; i32 in A:X;
   // i64 in A:X:Y plus DP $F0..$F1 for the highest half.  See
   // LowerReturn comment for the ABI.
-  if (Ins.size() > 4)
+  if (Ins.size() > 4) {
-    report_fatal_error("W65816: return type wider than 64 bits not supported");
+    reportUnsupported(DAG, DL,
+                      "return type wider than 64 bits is not supported");
+    for (const ISD::InputArg &I : Ins)
+      InVals.push_back(DAG.getUNDEF(I.VT)); // keep InVals aligned with Ins
+    return Chain;
+  }
 
   // Indirect calls (function pointers): redirect through the runtime
   // trampoline `__jsl_indir`.  The 65816 has no JSL-indirect; instead,
@@ -2187,8 +2227,14 @@ W65816TargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   }
 
   for (const ISD::OutputArg &O : Outs) {
-    if (O.VT != MVT::i16 && O.VT != MVT::i8 && O.VT != MVT::i32)
+    if (O.VT != MVT::i16 && O.VT != MVT::i8 && O.VT != MVT::i32) {
-      report_fatal_error("W65816: argument type not yet supported");
+      reportUnsupported(DAG, DL,
+                        "unsupported argument type (only i8/i16/i32 halves "
+                        "are representable in the W65816 ABI)");
+      for (const ISD::InputArg &I : Ins)
+        InVals.push_back(DAG.getUNDEF(I.VT)); // keep InVals aligned with Ins
+      return Chain;
+    }
   }
 
   // i32 first-arg ABI.  Two flavors:
@@ -2343,6 +2389,7 @@ W65816TargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   // walk it, copying from A, X, Y, DPF0 in order.  Re-assemble i32
   // halves into a Wide32 SDValue at the end.
   SmallVector<MVT, 4> ExpVT;
+  bool BadRet = false;
   for (unsigned i = 0, e = Ins.size(); i != e; ++i) {
     MVT VT = Ins[i].VT;
     if (VT == MVT::i32) {
@@ -2351,11 +2398,22 @@ W65816TargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
     } else if (VT == MVT::i16 || VT == MVT::i8) {
       ExpVT.push_back(VT);
     } else {
-      report_fatal_error("W65816: return half must be i8/i16/i32");
+      reportUnsupported(DAG, DL,
+                        "unsupported return value type (only i8/i16/i32 "
+                        "halves are representable in the W65816 ABI)");
+      BadRet = true;
     }
   }
-  if (ExpVT.size() > 4)
+  if (!BadRet && ExpVT.size() > 4) {
-    report_fatal_error("W65816: return type wider than 64 bits not supported");
+    reportUnsupported(DAG, DL,
+                      "return type wider than 64 bits is not supported");
+    BadRet = true;
+  }
+  if (BadRet) {
+    for (const ISD::InputArg &I : Ins)
+      InVals.push_back(DAG.getUNDEF(I.VT)); // keep InVals aligned with Ins
+    return Chain;
+  }
   static constexpr Register RetRegs[4] = {W65816::A, W65816::X, W65816::Y,
                                           W65816::DPF0};
   SmallVector<SDValue, 4> Halves;
@@ -2414,11 +2472,17 @@ SDValue W65816TargetLowering::LowerReturn(
       ExpVT.push_back(VT);
       ExpVals.push_back(OutVals[i]);
     } else {
-      report_fatal_error("W65816: return half must be i8/i16/i32");
+      reportUnsupported(DAG, DL,
+                        "unsupported return value type (only i8/i16/i32 "
+                        "halves are representable in the W65816 ABI)");
+      return DAG.getNode(W65816ISD::RET_GLUE, DL, MVT::Other, Chain);
     }
   }
-  if (ExpVT.size() > 4)
+  if (ExpVT.size() > 4) {
-    report_fatal_error("W65816: return type wider than 64 bits not supported");
+    reportUnsupported(DAG, DL,
+                      "return type wider than 64 bits is not supported");
+    return DAG.getNode(W65816ISD::RET_GLUE, DL, MVT::Other, Chain);
+  }
 
   // Single whole-i32 return: copy directly to AX32 instead of two
   // halves to A and X.  Saves the regalloc/coalescer some work.

src/llvm/lib/Target/W65816/W65816InstrInfo.td

@@ -581,8 +581,11 @@ def ASRA16 : W65816Pseudo<(outs Acc16:$dst), (ins Acc16:$src),
 }
 
 // Shifts by small constants — unroll into 2-4 single-bit shifts.
-// Anything beyond 4 bits would benefit from a loop or a XBA-and-mask
+// Counts >= 8 use the XBA-and-mask trick via the SHL8A/SRL8A pseudos
-// trick; left for a future peephole.
+// below, and counts 9..15 chain ASL/LSR after that pseudo (see the
+// SHL8A / SHL15A definitions and the 9..14 Pat blocks); counts 5..7
+// fall out of the generic combiner as ASL/LSR chains.  So every
+// constant shift 0..15 lowers inline (no __ashl/__lshr libcall).
 def : Pat<(shl Acc16:$src, (i16 2)), (ASLA16 (ASLA16 Acc16:$src))>;
 def : Pat<(shl Acc16:$src, (i16 3)),
           (ASLA16 (ASLA16 (ASLA16 Acc16:$src)))>;
@@ -1762,6 +1765,7 @@ def JML_Long       : InstAbsLong<0x5C, "jml">;
 //---------------------------------------------------------------- Calls
 let isCall = 1, mayLoad = 0, mayStore = 0 in {
 def JSR_Abs     : InstAbs<0x20, "jsr">;
+def JSR_AbsIndX : InstAbsIndX<0xFC, "jsr">;
 def JSL_Long    : InstAbsLong<0x22, "jsl">;
 }
 

src/llvm/lib/Target/W65816/W65816MCInstLower.cpp

@@ -7,8 +7,9 @@
 //===----------------------------------------------------------------------===//
 //
 // This file contains code to lower W65816 MachineInstrs to their
-// corresponding MCInst records.  The skeleton follows the MSP430 pattern
+// corresponding MCInst records, following the MSP430 pattern.  It handles
-// closely but does not yet understand any target-specific operand flags.
+// register, immediate, global/external-symbol, block-address, jump-table,
+// and constant-pool operands (see LowerSymbolOperand).
 //
 //===----------------------------------------------------------------------===//