[Hexagon][llvm-objdump] Improve disassembly of Hexagon bundles (#145807)

Hexagon instructions are VLIW "bundles" of up to four instruction words
encoded as a single MCInst with operands for each sub-instruction.
Previously, the disassembler's getInstruction() returned the full
bundle, which made it difficult to work with llvm-objdump.

For example, since all instructions are bundles, and bundles do not
branch, branch targets could not be printed.

This patch modifies the Hexagon disassembler to return individual
sub-instructions instead of entire bundles, enabling correct printing of
branch targets and relocations. It also introduces
`MCDisassembler::getInstructionBundle` for cases where the full bundle
is still needed.

By default, llvm-objdump separates instructions with newlines. However,
this does not work well for Hexagon syntax:

  { inst1
    inst2
    inst3
    inst4 <branch> } :endloop0

Instructions may be followed by a closing brace, a closing brace with
`:endloop`, or a newline. Branches must appear within the braces.

To address this, `PrettyPrinter::getInstructionSeparator()` is added and
overridden for Hexagon.

Author: quic-areg

lld/test/ELF/hexagon-plt.s

@@ -30,31 +30,31 @@
 # DIS:      <_start>:
 ## Direct call
 ## Call foo directly
-# DIS-NEXT:   { call 0x2003c }
+# DIS-NEXT:   { call 0x2003c <foo> }
 ## Call bar via plt
-# DIS-NEXT:   { call 0x20060 }
+# DIS-NEXT:   { call 0x20060 <bar@plt> }
 ## Call weak via plt
-# DIS-NEXT:   { call 0x20070 }
+# DIS-NEXT:   { call 0x20070 <weak@plt> }
 # DIS-NEXT: { 	immext(#0)
 
 ## Call foo directly
-# DIS-NEXT: if (p0) jump:nt 0x2003c }
+# DIS-NEXT: if (p0) jump:nt 0x2003c <foo> }
 # DIS-NEXT: { 	immext(#64)
 ## Call bar via plt
-# DIS-NEXT: if (p0) jump:nt 0x20060 }
+# DIS-NEXT: if (p0) jump:nt 0x20060 <bar@plt> }
 # DIS-NEXT: { 	immext(#64)
 ## Call weak via plt
-# DIS-NEXT: if (p0) jump:nt 0x20070 }
+# DIS-NEXT: if (p0) jump:nt 0x20070 <weak@plt> }
 # DIS-NEXT: { 	immext(#0)
 
 ## Call foo directly
-# DIS-NEXT: r0 = #0 ; jump 0x2003c }
+# DIS-NEXT: r0 = #0 ; jump 0x2003c <foo> }
 # DIS-NEXT: { 	immext(#0)
 ## Call bar via plt
-# DIS-NEXT: r0 = #0 ; jump 0x20060 }
+# DIS-NEXT: r0 = #0 ; jump 0x20060 <bar@plt> }
 # DIS-NEXT: { 	immext(#0)
 ## Call weak via plt
-# DIS-NEXT: r0 = #0 ; jump 0x20070 }
+# DIS-NEXT: r0 = #0 ; jump 0x20070 <weak@plt> }
 
 # DIS:      <foo>:
 # DIS-NEXT:   2003c:

lld/test/ELF/hexagon-shared.s

@@ -88,7 +88,7 @@ pvar:
 # PLT-NEXT: jumpr r28 }
 
 # TEXT:  bc 00 01 00 000100bc
-# TEXT: { 	call 0x10300 }
+# TEXT: { 	call 0x10300 <bar@plt> }
 # TEXT: if (p0) jump:nt 0x10300
 # TEXT: r0 = #0 ; jump 0x10300
 # TEXT: r0 = add(r1,##-65548)

lld/test/ELF/hexagon-tls-gd-xform.s

@@ -18,10 +18,10 @@
 _start:
 .ifdef GDPLT
                         call x@gdplt
-# CHECK_GDPLT:  101ec: { call 0x10220 }
+# CHECK_GDPLT:  101ec: { call 0x10220 <__tls_get_addr@plt> }
 .else
                   call x
-# CHECK:  101b8: { call 0x101e0 }
+# CHECK:  101b8: { call 0x101e0 <x@plt> }
 .endif
 
 # CHECK_GDPLT:        10220: { immext(#0x20040)

llvm/include/llvm/MC/MCDisassembler/MCDisassembler.h

@@ -136,6 +136,18 @@ class LLVM_ABI MCDisassembler {
                                       ArrayRef<uint8_t> Bytes, uint64_t Address,
                                       raw_ostream &CStream) const = 0;
 
+  /// Returns the disassembly of an instruction bundle for VLIW architectures
+  /// like Hexagon.
+  ///
+  /// \param Instr    - An MCInst to populate with the contents of
+  /// the Bundle with sub-instructions encoded as Inst operands.
+  virtual DecodeStatus getInstructionBundle(MCInst &Instr, uint64_t &Size,
+                                            ArrayRef<uint8_t> Bytes,
+                                            uint64_t Address,
+                                            raw_ostream &CStream) const {
+    return Fail;
+  }
+
   /// Used to perform separate target specific disassembly for a particular
   /// symbol. May parse any prelude that precedes instructions after the
   /// start of a symbol, or the entire symbol.

llvm/lib/Target/Hexagon/Disassembler/HexagonDisassembler.cpp

@@ -43,12 +43,12 @@ namespace {
 class HexagonDisassembler : public MCDisassembler {
 public:
   std::unique_ptr<MCInstrInfo const> const MCII;
-  std::unique_ptr<MCInst *> CurrentBundle;
+  mutable std::unique_ptr<MCInst> CurrentBundle;
   mutable MCInst const *CurrentExtender;
 
   HexagonDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx,
                       MCInstrInfo const *MCII)
-      : MCDisassembler(STI, Ctx), MCII(MCII), CurrentBundle(new MCInst *),
+      : MCDisassembler(STI, Ctx), MCII(MCII), CurrentBundle(nullptr),
         CurrentExtender(nullptr) {}
 
   DecodeStatus getSingleInstruction(MCInst &Instr, MCInst &MCB,
@@ -57,7 +57,23 @@ class HexagonDisassembler : public MCDisassembler {
   DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size,
                               ArrayRef<uint8_t> Bytes, uint64_t Address,
                               raw_ostream &CStream) const override;
+
+  DecodeStatus getInstructionBundle(MCInst &Instr, uint64_t &Size,
+                                    ArrayRef<uint8_t> Bytes, uint64_t Address,
+                                    raw_ostream &CStream) const override;
+
   void remapInstruction(MCInst &Instr) const;
+
+private:
+  bool makeBundle(ArrayRef<uint8_t> Bytes, uint64_t Address,
+                  uint64_t &BytesToSkip, raw_ostream &CS) const;
+
+  void resetBundle() const {
+    CurrentBundle.reset();
+    CurrentInstruction = nullptr;
+  }
+
+  mutable MCOperand *CurrentInstruction = nullptr;
 };
 
 static uint64_t fullValue(HexagonDisassembler const &Disassembler, MCInst &MI,
@@ -171,43 +187,88 @@ LLVMInitializeHexagonDisassembler() {
                                          createHexagonDisassembler);
 }
 
-DecodeStatus HexagonDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
-                                                 ArrayRef<uint8_t> Bytes,
-                                                 uint64_t Address,
-                                                 raw_ostream &CS) const {
-  CommentStream = &CS;
-
-  DecodeStatus Result = DecodeStatus::Success;
+bool HexagonDisassembler::makeBundle(ArrayRef<uint8_t> Bytes, uint64_t Address,
+                                     uint64_t &BytesToSkip,
+                                     raw_ostream &CS) const {
   bool Complete = false;
-  Size = 0;
+  DecodeStatus Result = DecodeStatus::Success;
 
-  *CurrentBundle = &MI;
-  MI.setOpcode(Hexagon::BUNDLE);
-  MI.addOperand(MCOperand::createImm(0));
+  CurrentBundle.reset(new MCInst);
+  CurrentBundle->setOpcode(Hexagon::BUNDLE);
+  CurrentBundle->addOperand(MCOperand::createImm(0));
   while (Result == Success && !Complete) {
     if (Bytes.size() < HEXAGON_INSTR_SIZE)
-      return MCDisassembler::Fail;
+      return false;
     MCInst *Inst = getContext().createMCInst();
-    Result = getSingleInstruction(*Inst, MI, Bytes, Address, CS, Complete);
-    MI.addOperand(MCOperand::createInst(Inst));
-    Size += HEXAGON_INSTR_SIZE;
+    Result = getSingleInstruction(*Inst, *CurrentBundle, Bytes, Address, CS,
+                                  Complete);
+    CurrentBundle->addOperand(MCOperand::createInst(Inst));
+    BytesToSkip += HEXAGON_INSTR_SIZE;
     Bytes = Bytes.slice(HEXAGON_INSTR_SIZE);
   }
   if (Result == MCDisassembler::Fail)
-    return Result;
-  if (Size > HEXAGON_MAX_PACKET_SIZE)
-    return MCDisassembler::Fail;
+    return false;
+  if (BytesToSkip > HEXAGON_MAX_PACKET_SIZE)
+    return false;
 
   const auto ArchSTI = Hexagon_MC::getArchSubtarget(&STI);
   const auto STI_ = (ArchSTI != nullptr) ? *ArchSTI : STI;
-  HexagonMCChecker Checker(getContext(), *MCII, STI_, MI,
+  HexagonMCChecker Checker(getContext(), *MCII, STI_, *CurrentBundle,
                            *getContext().getRegisterInfo(), false);
   if (!Checker.check())
-    return MCDisassembler::Fail;
-  remapInstruction(MI);
+    return false;
+  remapInstruction(*CurrentBundle);
+  return true;
+}
+
+DecodeStatus HexagonDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
+                                                 ArrayRef<uint8_t> Bytes,
+                                                 uint64_t Address,
+                                                 raw_ostream &CS) const {
+  CommentStream = &CS;
+
+  Size = 0;
+  uint64_t BytesToSkip = 0;
+
+  if (!CurrentBundle) {
+    if (!makeBundle(Bytes, Address, BytesToSkip, CS)) {
+      Size = BytesToSkip;
+      resetBundle();
+      return MCDisassembler::Fail;
+    }
+    CurrentInstruction = (CurrentBundle->begin() + 1);
+  }
+
+  MI = *(CurrentInstruction->getInst());
+  Size = HEXAGON_INSTR_SIZE;
+  if (++CurrentInstruction == CurrentBundle->end())
+    resetBundle();
   return MCDisassembler::Success;
 }
 
+DecodeStatus HexagonDisassembler::getInstructionBundle(MCInst &MI,
+                                                       uint64_t &Size,
+                                                       ArrayRef<uint8_t> Bytes,
+                                                       uint64_t Address,
+                                                       raw_ostream &CS) const {
+  CommentStream = &CS;
+  Size = 0;
+  uint64_t BytesToSkip = 0;
+  assert(!CurrentBundle);
+
+  if (!makeBundle(Bytes, Address, BytesToSkip, CS)) {
+    Size = BytesToSkip;
+    resetBundle();
+    return MCDisassembler::Fail;
+  }
+
+  MI = *CurrentBundle;
+  Size = HEXAGON_INSTR_SIZE * HexagonMCInstrInfo::bundleSize(MI);
+  resetBundle();
+
+  return Success;
+}
+
 void HexagonDisassembler::remapInstruction(MCInst &Instr) const {
   for (auto I: HexagonMCInstrInfo::bundleInstructions(Instr)) {
     auto &MI = const_cast<MCInst &>(*I.getInst());
@@ -482,7 +543,7 @@ DecodeStatus HexagonDisassembler::getSingleInstruction(MCInst &MI, MCInst &MCB,
     unsigned Offset = 1;
     bool Vector = HexagonMCInstrInfo::isVector(*MCII, MI);
     bool PrevVector = false;
-    auto Instructions = HexagonMCInstrInfo::bundleInstructions(**CurrentBundle);
+    auto Instructions = HexagonMCInstrInfo::bundleInstructions(*CurrentBundle);
     auto i = Instructions.end() - 1;
     for (auto n = Instructions.begin() - 1;; --i, ++Offset) {
       if (i == n)

llvm/lib/Target/Hexagon/MCTargetDesc/HexagonInstPrinter.cpp

@@ -33,30 +33,18 @@ void HexagonInstPrinter::printRegName(raw_ostream &O, MCRegister Reg) {
 void HexagonInstPrinter::printInst(const MCInst *MI, uint64_t Address,
                                    StringRef Annot, const MCSubtargetInfo &STI,
                                    raw_ostream &OS) {
-  assert(HexagonMCInstrInfo::isBundle(*MI));
-  assert(HexagonMCInstrInfo::bundleSize(*MI) <= HEXAGON_PACKET_SIZE);
-  assert(HexagonMCInstrInfo::bundleSize(*MI) > 0);
-  HasExtender = false;
-  for (auto const &I : HexagonMCInstrInfo::bundleInstructions(*MI)) {
-    MCInst const &MCI = *I.getInst();
-    if (HexagonMCInstrInfo::isDuplex(MII, MCI)) {
-      printInstruction(MCI.getOperand(1).getInst(), Address, OS);
-      OS << '\v';
-      HasExtender = false;
-      printInstruction(MCI.getOperand(0).getInst(), Address, OS);
-    } else
-      printInstruction(&MCI, Address, OS);
-    HasExtender = HexagonMCInstrInfo::isImmext(MCI);
-    OS << "\n";
-  }
-
-  bool IsLoop0 = HexagonMCInstrInfo::isInnerLoop(*MI);
-  bool IsLoop1 = HexagonMCInstrInfo::isOuterLoop(*MI);
-  if (IsLoop0) {
-    OS << (IsLoop1 ? " :endloop01" : " :endloop0");
-  } else if (IsLoop1) {
-    OS << " :endloop1";
+  if (HexagonMCInstrInfo::isDuplex(MII, *MI)) {
+    printInstruction(MI->getOperand(1).getInst(), Address, OS);
+    OS << '\v';
+    HasExtender = false;
+    printInstruction(MI->getOperand(0).getInst(), Address, OS);
+  } else {
+    printInstruction(MI, Address, OS);
   }
+  HasExtender = HexagonMCInstrInfo::isImmext(*MI);
+  if ((MI->getOpcode() & HexagonII::INST_PARSE_MASK) ==
+      HexagonII::INST_PARSE_PACKET_END)
+    HasExtender = false;
 }
 
 void HexagonInstPrinter::printOperand(MCInst const *MI, unsigned OpNo,

llvm/lib/Target/Hexagon/MCTargetDesc/HexagonMCTargetDesc.cpp

@@ -252,8 +252,21 @@ class HexagonTargetAsmStreamer : public HexagonTargetStreamer {
     std::string Buffer;
     {
       raw_string_ostream TempStream(Buffer);
-      InstPrinter.printInst(&Inst, Address, "", STI, TempStream);
+      for (auto &I : HexagonMCInstrInfo::bundleInstructions(Inst)) {
+        InstPrinter.printInst(I.getInst(), Address, "", STI, TempStream);
+        TempStream << "\n";
+      }
+    }
+
+    std::string LoopString = "";
+    bool IsLoop0 = HexagonMCInstrInfo::isInnerLoop(Inst);
+    bool IsLoop1 = HexagonMCInstrInfo::isOuterLoop(Inst);
+    if (IsLoop0) {
+      LoopString += (IsLoop1 ? " :endloop01" : " :endloop0");
+    } else if (IsLoop1) {
+      LoopString += " :endloop1";
     }
+
     StringRef Contents(Buffer);
     auto PacketBundle = Contents.rsplit('\n');
     auto HeadTail = PacketBundle.first.split('\n');
@@ -275,9 +288,9 @@ class HexagonTargetAsmStreamer : public HexagonTargetStreamer {
     }
 
     if (HexagonMCInstrInfo::isMemReorderDisabled(Inst))
-      OS << "\n\t} :mem_noshuf" << PacketBundle.second;
+      OS << "\n\t} :mem_noshuf" << LoopString;
     else
-      OS << "\t}" << PacketBundle.second;
+      OS << "\t}" << LoopString;
   }
 
   void finish() override { finishAttributeSection(); }

llvm/test/MC/Hexagon/two_ext.s

@@ -6,7 +6,7 @@
   if (!p1) call foo_b
 }
 # CHECK: 00004000 { immext(#0)
-# CHECK: 5d004100   if (p1) call 0x0
+# CHECK: 5d004100   if (p1) call 0x0 <.text>
 # CHECK: 00004000   immext(#0)
-# CHECK: 5d20c100   if (!p1) call 0x0 }
+# CHECK: 5d20c100   if (!p1) call 0x0 <.text> }
 

llvm/test/tools/llvm-objdump/ELF/Hexagon/hexagon-bundles.s

@@ -0,0 +1,47 @@
+/// Checks that various hexagon scenarios are handled correctly:
+///  - branch targets
+///  - endloops
+///  - inline-relocs
+///  - multi-insn bundles
+
+{
+  r6 = sub(r1, r0)
+  r7 = and(r4, #0x0)
+  if (p1) jump:t target1
+  if (p2) jump:nt target2
+}
+
+{
+  r8 = r7
+  r9 = add(r8, #0)
+  r10 = memw(r9)
+} :endloop0
+
+{ jump ##sym }
+
+target1:
+  nop
+
+target2:
+  nop
+
+// RUN: llvm-mc %s --triple=hexagon -filetype=obj | llvm-objdump -d -r - | FileCheck %s
+
+//      CHECK: 00000000 <.text>:
+// CHECK-NEXT:        0:       12 51 00 5c     5c005112 {      if (p1) jump:t 0x24 <target1>
+// CHECK-NEXT:        4:       14 42 00 5c     5c004214        if (p2) jump:nt 0x28 <target2>
+// CHECK-NEXT:        8:       06 41 20 f3     f3204106        r6 = sub(r1,r0)
+// CHECK-NEXT:        c:       07 c0 04 76     7604c007        r7 = and(r4,#0x0) }
+// CHECK-NEXT:       10:       08 80 67 70     70678008 {      r8 = r7
+// CHECK-NEXT:       14:       09 40 08 b0     b0084009        r9 = add(r8,#0x0)
+// CHECK-NEXT:       18:       0a c0 89 91     9189c00a        r10 = memw(r9+#0x0) }  :endloop0
+// CHECK-NEXT:       1c:       00 40 00 00     00004000 {      immext(#0x0)
+// CHECK-NEXT:                         0000001c:  R_HEX_B32_PCREL_X    sym
+// CHECK-NEXT:       20:       00 c0 00 58     5800c000        jump 0x1c <.text+0x1c> }
+// CHECK-NEXT:                         00000020:  R_HEX_B22_PCREL_X    sym+0x4
+// CHECK-EMPTY:
+// CHECK-NEXT: 00000024 <target1>:
+// CHECK-NEXT:       24:       00 c0 00 7f     7f00c000 {      nop }
+// CHECK-EMPTY:
+// CHECK-NEXT: 00000028 <target2>:
+// CHECK-NEXT:       28:       00 c0 00 7f     7f00c000 {      nop }

llvm/tools/llvm-mc/Disassembler.cpp

@@ -45,7 +45,11 @@ static bool PrintInsts(const MCDisassembler &DisAsm, const ByteArrayTy &Bytes,
     MCInst Inst;
 
     MCDisassembler::DecodeStatus S;
-    S = DisAsm.getInstruction(Inst, Size, Data.slice(Index), Index, nulls());
+    if (STI.getTargetTriple().getArch() == Triple::hexagon)
+      S = DisAsm.getInstructionBundle(Inst, Size, Data.slice(Index), Index,
+                                      nulls());
+    else
+      S = DisAsm.getInstruction(Inst, Size, Data.slice(Index), Index, nulls());
     switch (S) {
     case MCDisassembler::Fail:
       SM.PrintMessage(SMLoc::getFromPointer(Bytes.second[Index]),