[MachineInstr] Add a dumpr method

[qcolombet]

Summary

Add a dump method that recursively prints an instruction and all
the instructions defining its operands and so on.

This is helpful when looking at combiner issue.

NFC

[arsenm]

llvm/include/llvm/CodeGen/MachineInstr.h

1545

I think defaulting to UINT_MAX would be simpler than the optional here, especially since debuggers are really bad at calling functions with nontrivial arguments

llvm/lib/CodeGen/MachineInstr.cpp

1474–1476

Can you avoid doing this manually with formatted_raw_ostream?

[qcolombet]

llvm/include/llvm/CodeGen/MachineInstr.h

1545

Good point, will change that.

llvm/lib/CodeGen/MachineInstr.cpp

1474–1476

Forgot about that one. Looking.

[qcolombet]

• Use UINT_MAX instead of Optional to ease the use of the method in the debugger
• Use the dedicated formatted_raw_ostream to pad column

[qcolombet]

• Handle PhysReg and Non-SSA code in general

[qcolombet]

Here are a few examples of the dump we get:

• No Depth limit:

(lldb) p MI.dumpr(MRI, -1)
%1:_(<4 x s16>) = G_BUILD_VECTOR %6:_(s16), %7:_(s16), %8:_(s16), %9:_(s16)
  %6:_(s16) = G_FPTRUNC %17:_(s32)
    %17:_(s32) = COPY $s0
  %7:_(s16) = G_FPTRUNC %15:_(s32)
    %15:_(s32) = COPY $s0
  %8:_(s16) = G_FPTRUNC %13:_(s32)
    %13:_(s32) = COPY $s0
  %9:_(s16) = G_FPTRUNC %11:_(s32)
    %11:_(s32) = COPY $s0

• Depth limit of 2:

(lldb) p MI.dumpr(MRI, 2)
%1:_(<4 x s16>) = G_BUILD_VECTOR %6:_(s16), %7:_(s16), %8:_(s16), %9:_(s16)
  %6:_(s16) = G_FPTRUNC %17:_(s32)
  %7:_(s16) = G_FPTRUNC %15:_(s32)
  %8:_(s16) = G_FPTRUNC %13:_(s32)
  %9:_(s16) = G_FPTRUNC %11:_(s32)

[arsenm]

LGTM with nit

llvm/lib/CodeGen/MachineInstr.cpp

1483

Reg.isPhysical

1485–1486

I think the !( looks weird so you could juts move the assignment to the definition

llvm/include/llvm/CodeGen/MachineInstr.h

private:
   /// It reserves space for number of operands specified by
   /// MCInstrDesc.  An explicit DebugLoc is supplied.
   MachineInstr(MachineFunction &, const MCInstrDesc &tid, DebugLoc dl,
                bool NoImp = false);
 
   // MachineInstrs are pool-allocated and owned by MachineFunction.
   friend class MachineFunction;
 
+  void
+  dumprImpl(const MachineRegisterInfo &MRI, unsigned Depth,
+            Optional<unsigned> MaxDepth,
+            SmallPtrSetImpl<const MachineInstr *> &AlreadySeenInstrs) const;
+
 public:
   MachineInstr(const MachineInstr &) = delete;
   MachineInstr &operator=(const MachineInstr &) = delete;
   // Use MachineFunction::DeleteMachineInstr() instead.
   ~MachineInstr() = delete;
 
   const MachineBasicBlock* getParent() const { return Parent; }
   MachineBasicBlock* getParent() { return Parent; }

   void print(raw_ostream &OS, bool IsStandalone = true, bool SkipOpers = false,
              bool SkipDebugLoc = false, bool AddNewLine = true,
              const TargetInstrInfo *TII = nullptr) const;
   void print(raw_ostream &OS, ModuleSlotTracker &MST, bool IsStandalone = true,
              bool SkipOpers = false, bool SkipDebugLoc = false,
              bool AddNewLine = true,
              const TargetInstrInfo *TII = nullptr) const;
   void dump() const;
+  /// Print on dbgs() the current instruction and the instructions defining its
+  /// operands and so on until we reach \p MaxDepth.
+  void dumpr(const MachineRegisterInfo &MRI,
+             Optional<unsigned> MaxDepth = None) const;
   /// @}
 
   //===--------------------------------------------------------------------===//
   // Accessors used to build up machine instructions.
 
   /// Add the specified operand to the instruction.  If it is an implicit
   /// operand, it is added to the end of the operand list.  If it is an
   /// explicit operand it is added at the end of the explicit operand list

llvm/lib/CodeGen/MachineInstr.cpp

LLT MachineInstr::getTypeToPrint(unsigned OpIdx, SmallBitVector &PrintedTypes,
   return TypeToPrint;
 }
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD void MachineInstr::dump() const {
   dbgs() << "  ";
   print(dbgs());
 }
+
+LLVM_DUMP_METHOD void MachineInstr::dumprImpl(
+    const MachineRegisterInfo &MRI, unsigned Depth, Optional<unsigned> MaxDepth,
+    SmallPtrSetImpl<const MachineInstr *> &AlreadySeenInstrs) const {
+  if (MaxDepth && Depth >= *MaxDepth)
+    return;
+  if (!AlreadySeenInstrs.insert(this).second)
+    return;
+  std::string Prefix;
+  for (unsigned i = 0; i != Depth; ++i)
+    Prefix += "  ";
+  dbgs() << Prefix;
+  dump();
+  for (const MachineOperand &MO : operands()) {
+    const MachineInstr *NewMI;
+    if (!MO.isReg() || MO.isDef() || !(NewMI = MRI.getVRegDef(MO.getReg())))
+      continue;
+    NewMI->dumprImpl(MRI, Depth + 1, MaxDepth, AlreadySeenInstrs);
+  }
+}
+
+LLVM_DUMP_METHOD void MachineInstr::dumpr(const MachineRegisterInfo &MRI,
+                                          Optional<unsigned> MaxDepth) const {
+  SmallPtrSet<const MachineInstr *, 16> AlreadySeenInstrs;
+  dumprImpl(MRI, 0, MaxDepth, AlreadySeenInstrs);
+}
 #endif
 
 void MachineInstr::print(raw_ostream &OS, bool IsStandalone, bool SkipOpers,
                          bool SkipDebugLoc, bool AddNewLine,
                          const TargetInstrInfo *TII) const {
   const Module *M = nullptr;
   const Function *F = nullptr;
   if (const MachineFunction *MF = getMFIfAvailable(*this)) {