[GlobalISel] Fix inserting copies in the right position for reg definitions

When constrainRegClass is called if the constraining happens on a use the COPY
needs to be inserted before the instruction that contains the MachineOperand,
but if we are constraining a definition it actually needs to be added
after the instruction. In addition, the COPY needs to have its operands
flipped (in the use case we are copying from the old unconstrained register
to the new constrained register, while in the definition case we are copying
from the new constrained register that the instruction defines to the old
unconstrained register).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@359282 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/GlobalISel/Utils.h b/include/llvm/CodeGen/GlobalISel/Utils.h
index 4e3a24c7b111a30b5854f1736863135bc1eb5a03..634b8d976e17da7afc7473dc74bb137424ff0a06 100644 (file)
--- a/include/llvm/CodeGen/GlobalISel/Utils.h
+++ b/include/llvm/CodeGen/GlobalISel/Utils.h
@@ -36,21 +36,37 @@ class ConstantFP;
 class APFloat;
 
 /// 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.
+/// create a new virtual register in the correct class.
 ///
 /// \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 RegisterBankInfo &RBI, unsigned Reg,
                              const TargetRegisterClass &RegClass);
 
+/// Constrain the Register operand OpIdx, so that it is now constrained to the
+/// TargetRegisterClass passed as an argument (RegClass).
+/// If this fails, create a new virtual register in the correct class and
+/// insert a COPY before \p InsertPt if it is a use or after if it is a
+/// definition. 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,
+                                  const TargetRegisterInfo &TRI,
+                                  MachineRegisterInfo &MRI,
+                                  const TargetInstrInfo &TII,
+                                  const RegisterBankInfo &RBI,
+                                  MachineInstr &InsertPt,
+                                  const TargetRegisterClass &RegClass,
+                                  const MachineOperand &RegMO, unsigned OpIdx);
+
 /// 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.
-/// This is equivalent to constrainRegToClass() with RegClass obtained from the
-/// MCInstrDesc. The debug location of \p InsertPt is used for the new copy.
+/// register in the correct class and insert a COPY before \p InsertPt
+/// if it is a use or after if it is a definition.
+/// This is equivalent to constrainOperandRegClass(..., RegClass, ...)
+/// 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,

diff --git a/lib/CodeGen/GlobalISel/InstructionSelector.cpp b/lib/CodeGen/GlobalISel/InstructionSelector.cpp
index a449e9dec41be67b16d52be3836d70090ec09b78..ca6d864053113d07553e9b4d4343ed64f2b3963f 100644 (file)
--- a/lib/CodeGen/GlobalISel/InstructionSelector.cpp
+++ b/lib/CodeGen/GlobalISel/InstructionSelector.cpp
@@ -41,8 +41,8 @@ bool InstructionSelector::constrainOperandRegToRegClass(
   MachineFunction &MF = *MBB.getParent();
   MachineRegisterInfo &MRI = MF.getRegInfo();
 
-  return
-      constrainRegToClass(MRI, TII, RBI, I, I.getOperand(OpIdx).getReg(), RC);
+  return constrainOperandRegClass(MF, TRI, MRI, TII, RBI, I, RC,
+                                  I.getOperand(OpIdx), OpIdx);
 }
 
 bool InstructionSelector::isOperandImmEqual(

diff --git a/lib/CodeGen/GlobalISel/Utils.cpp b/lib/CodeGen/GlobalISel/Utils.cpp
index d65328be39c0b477e99963814505cd84af3e3e99..1018c26ece49c88e14414f1ebc5348dfa276e826 100644 (file)
--- a/lib/CodeGen/GlobalISel/Utils.cpp
+++ b/lib/CodeGen/GlobalISel/Utils.cpp
@@ -29,20 +29,45 @@ using namespace llvm;
 
 unsigned llvm::constrainRegToClass(MachineRegisterInfo &MRI,
                                    const TargetInstrInfo &TII,
-                                   const RegisterBankInfo &RBI,
-                                   MachineInstr &InsertPt, unsigned Reg,
+                                   const RegisterBankInfo &RBI, unsigned Reg,
                                    const TargetRegisterClass &RegClass) {
-  if (!RBI.constrainGenericRegister(Reg, RegClass, MRI)) {
-    unsigned NewReg = MRI.createVirtualRegister(&RegClass);
-    BuildMI(*InsertPt.getParent(), InsertPt, InsertPt.getDebugLoc(),
-            TII.get(TargetOpcode::COPY), NewReg)
-        .addReg(Reg);
-    return NewReg;
-  }
+  if (!RBI.constrainGenericRegister(Reg, RegClass, MRI))
+    return MRI.createVirtualRegister(&RegClass);
 
   return Reg;
 }
 
+unsigned llvm::constrainOperandRegClass(
+    const MachineFunction &MF, const TargetRegisterInfo &TRI,
+    MachineRegisterInfo &MRI, const TargetInstrInfo &TII,
+    const RegisterBankInfo &RBI, MachineInstr &InsertPt,
+    const TargetRegisterClass &RegClass, const MachineOperand &RegMO,
+    unsigned OpIdx) {
+  unsigned Reg = RegMO.getReg();
+  // Assume physical registers are properly constrained.
+  assert(TargetRegisterInfo::isVirtualRegister(Reg) &&
+         "PhysReg not implemented");
+
+  unsigned ConstrainedReg = constrainRegToClass(MRI, TII, RBI, Reg, RegClass);
+  // If we created a new virtual register because the class is not compatible
+  // then create a copy between the new and the old register.
+  if (ConstrainedReg != Reg) {
+    MachineBasicBlock::iterator InsertIt(&InsertPt);
+    MachineBasicBlock &MBB = *InsertPt.getParent();
+    if (RegMO.isUse()) {
+      BuildMI(MBB, InsertIt, InsertPt.getDebugLoc(),
+              TII.get(TargetOpcode::COPY), ConstrainedReg)
+          .addReg(Reg);
+    } else {
+      assert(RegMO.isDef() && "Must be a definition");
+      BuildMI(MBB, std::next(InsertIt), InsertPt.getDebugLoc(),
+              TII.get(TargetOpcode::COPY), Reg)
+          .addReg(ConstrainedReg);
+    }
+  }
+  return ConstrainedReg;
+}
+
 unsigned llvm::constrainOperandRegClass(
     const MachineFunction &MF, const TargetRegisterInfo &TRI,
     MachineRegisterInfo &MRI, const TargetInstrInfo &TII,
@@ -81,7 +106,8 @@ unsigned llvm::constrainOperandRegClass(
     // and they never reach this function.
     return Reg;
   }
-  return constrainRegToClass(MRI, TII, RBI, InsertPt, Reg, *RegClass);
+  return constrainOperandRegClass(MF, TRI, MRI, TII, RBI, InsertPt, *RegClass,
+                                  RegMO, OpIdx);
 }
 
 bool llvm::constrainSelectedInstRegOperands(MachineInstr &I,