[MachineInstr] Add a dumpr method

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

Differential Revision: https://reviews.llvm.org/D75094

llvm/include/llvm/CodeGen/MachineInstr.h

@@ -262,6 +262,10 @@ private:
   // MachineInstrs are pool-allocated and owned by MachineFunction.
   friend class MachineFunction;
 
+  void
+  dumprImpl(const MachineRegisterInfo &MRI, unsigned Depth, unsigned MaxDepth,
+            SmallPtrSetImpl<const MachineInstr *> &AlreadySeenInstrs) const;
+
 public:
   MachineInstr(const MachineInstr &) = delete;
   MachineInstr &operator=(const MachineInstr &) = delete;
@@ -1534,6 +1538,10 @@ public:
              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,
+             unsigned MaxDepth = UINT_MAX) const;
   /// @}
 
   //===--------------------------------------------------------------------===//

llvm/lib/CodeGen/MachineInstr.cpp

@@ -61,6 +61,7 @@
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/FormattedStream.h"
 #include "llvm/Support/LowLevelTypeImpl.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
@@ -1463,6 +1464,37 @@ LLVM_DUMP_METHOD void MachineInstr::dump() const {
   dbgs() << "  ";
   print(dbgs());
 }
+
+LLVM_DUMP_METHOD void MachineInstr::dumprImpl(
+    const MachineRegisterInfo &MRI, unsigned Depth, unsigned MaxDepth,
+    SmallPtrSetImpl<const MachineInstr *> &AlreadySeenInstrs) const {
+  if (Depth >= MaxDepth)
+    return;
+  if (!AlreadySeenInstrs.insert(this).second)
+    return;
+  // PadToColumn always inserts at least one space.
+  // Don't mess up the alignment if we don't want any space.
+  if (Depth)
+    fdbgs().PadToColumn(Depth * 2);
+  print(fdbgs());
+  for (const MachineOperand &MO : operands()) {
+    if (!MO.isReg() || MO.isDef())
+      continue;
+    Register Reg = MO.getReg();
+    if (Reg.isPhysical())
+      continue;
+    const MachineInstr *NewMI = MRI.getUniqueVRegDef(Reg);
+    if (NewMI == nullptr)
+      continue;
+    NewMI->dumprImpl(MRI, Depth + 1, MaxDepth, AlreadySeenInstrs);
+  }
+}
+
+LLVM_DUMP_METHOD void MachineInstr::dumpr(const MachineRegisterInfo &MRI,
+                                          unsigned MaxDepth) const {
+  SmallPtrSet<const MachineInstr *, 16> AlreadySeenInstrs;
+  dumprImpl(MRI, 0, MaxDepth, AlreadySeenInstrs);
+}
 #endif
 
 void MachineInstr::print(raw_ostream &OS, bool IsStandalone, bool SkipOpers,