[globalisel][tablegen] Add support for COPY_TO_REGCLASS.

Summary:
As part of this
* Emitted instructions now have named MachineInstr variables associated
  with them. This isn't particularly important yet but it's a small step
  towards multiple-insn emission.
* constrainSelectedInstRegOperands() is no longer hardcoded. It's now added
  as the ConstrainOperandsToDefinitionAction() action. COPY_TO_REGCLASS uses
  an alternate constraint mechanism ConstrainOperandToRegClassAction() which
  supports arbitrary constraints such as that defined by COPY_TO_REGCLASS.

Reviewers: ab, qcolombet, t.p.northover, rovka, kristof.beyls, aditya_nandakumar

Reviewed By: ab

Subscribers: javed.absar, igorb, llvm-commits

Differential Revision: https://reviews.llvm.org/D33590

llvm-svn: 305791

2 files changed, 25 insertions, 1 deletions

diff --git a/llvm/include/llvm/CodeGen/GlobalISel/InstructionSelector.h b/llvm/include/llvm/CodeGen/GlobalISel/InstructionSelector.h
index 1a865c3f0dc..b3ef7c2dc18 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/InstructionSelector.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/InstructionSelector.h
@@ -29,6 +29,7 @@ class MachineOperand;
 class MachineRegisterInfo;
 class RegisterBankInfo;
 class TargetInstrInfo;
+class TargetRegisterClass;
 class TargetRegisterInfo;
 
 /// Container class for CodeGen predicate results.
@@ -79,6 +80,16 @@ protected:
 
   InstructionSelector();
 
+  /// Constrain a register operand of an instruction \p I to a specified
+  /// register class. This could involve inserting COPYs before (for uses) or
+  /// after (for defs) and may replace the operand of \p I.
+  /// \returns whether operand regclass constraining succeeded.
+  bool constrainOperandRegToRegClass(MachineInstr &I, unsigned OpIdx,
+                                     const TargetRegisterClass &RC,
+                                     const TargetInstrInfo &TII,
+                                     const TargetRegisterInfo &TRI,
+                                     const RegisterBankInfo &RBI) const;
+
   /// Mutate the newly-selected instruction \p I to constrain its (possibly
   /// generic) virtual register operands to the instruction's register class.
   /// This could involve inserting COPYs before (for uses) or after (for defs).
diff --git a/llvm/include/llvm/CodeGen/GlobalISel/Utils.h b/llvm/include/llvm/CodeGen/GlobalISel/Utils.h
index 69d50706980..50ddbeb9432 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/Utils.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/Utils.h
@@ -29,13 +29,26 @@ class RegisterBankInfo;
 class TargetInstrInfo;
 class TargetPassConfig;
 class TargetRegisterInfo;
+class TargetRegisterClass;
 class Twine;
 class ConstantFP;
 
+/// Try to constrain Reg to the specified register class. If this fails,
+/// create a new virtual register in the correct class and insert a COPY before
+/// \p InsertPt. The debug location of \p InsertPt is used for the new copy.
+///
+/// \return The virtual register constrained to the right register class.
+unsigned constrainRegToClass(MachineRegisterInfo &MRI,
+                             const TargetInstrInfo &TII,
+                             const RegisterBankInfo &RBI,
+                             MachineInstr &InsertPt, unsigned Reg,
+                             const TargetRegisterClass &RegClass);
+
 /// Try to constrain Reg so that it is usable by argument OpIdx of the
 /// provided MCInstrDesc \p II. If this fails, create a new virtual
 /// register in the correct class and insert a COPY before \p InsertPt.
-/// The debug location of \p InsertPt is used for the new copy.
+/// This is equivalent to constrainRegToClass() with RegClass obtained from the
+/// MCInstrDesc. The debug location of \p InsertPt is used for the new copy.
 ///
 /// \return The virtual register constrained to the right register class.
 unsigned constrainOperandRegClass(const MachineFunction &MF,