FastISel: constrain the RegClass of operands when emitting instructions.

ARM64 suffered multiple -verify-machineinstr failures (principally over the
xsp/xzr issue) because FastISel was completely ignoring which subset of the
general-purpose registers each instruction required.

More fixes are coming in ARM64 specific FastISel, but this should cover the
generic problems.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206283 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/FastISel.h

@@ -343,6 +343,12 @@ protected:
 
   unsigned createResultReg(const TargetRegisterClass *RC);
 
+  /// Try to constrain Op so that it is usable by argument OpNum of the provided
+  /// MCInstrDesc. If this fails, create a new virtual register in the correct
+  /// class and COPY the value there.
+  unsigned constrainOperandRegClass(const MCInstrDesc &II, unsigned Op,
+                                    unsigned OpNum);
+
   /// Emit a constant in a register using target-specific logic, such as
   /// constant pool loads.
   virtual unsigned TargetMaterializeConstant(const Constant* C) {

lib/CodeGen/SelectionDAG/FastISel.cpp

@@ -1204,6 +1204,23 @@ unsigned FastISel::createResultReg(const TargetRegisterClass* RC) {
   return MRI.createVirtualRegister(RC);
 }
 
+unsigned FastISel::constrainOperandRegClass(const MCInstrDesc &II,
+                                            unsigned Op, unsigned OpNum) {
+  if (TargetRegisterInfo::isVirtualRegister(Op)) {
+    const TargetRegisterClass *RegClass =
+        TII.getRegClass(II, OpNum, &TRI, *FuncInfo.MF);
+    if (!MRI.constrainRegClass(Op, RegClass)) {
+      // If it's not legal to COPY between the register classes, something
+      // has gone very wrong before we got here.
+      unsigned NewOp = createResultReg(RegClass);
+      BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
+              TII.get(TargetOpcode::COPY), NewOp).addReg(Op);
+      return NewOp;
+    }
+  }
+  return Op;
+}
+
 unsigned FastISel::FastEmitInst_(unsigned MachineInstOpcode,
                                  const TargetRegisterClass* RC) {
   unsigned ResultReg = createResultReg(RC);
@@ -1216,9 +1233,11 @@ unsigned FastISel::FastEmitInst_(unsigned MachineInstOpcode,
 unsigned FastISel::FastEmitInst_r(unsigned MachineInstOpcode,
                                   const TargetRegisterClass *RC,
                                   unsigned Op0, bool Op0IsKill) {
-  unsigned ResultReg = createResultReg(RC);
   const MCInstrDesc &II = TII.get(MachineInstOpcode);
 
+  unsigned ResultReg = createResultReg(RC);
+  Op0 = constrainOperandRegClass(II, Op0, II.getNumDefs());
+
   if (II.getNumDefs() >= 1)
     BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, II, ResultReg)
       .addReg(Op0, Op0IsKill * RegState::Kill);
@@ -1236,9 +1255,12 @@ unsigned FastISel::FastEmitInst_rr(unsigned MachineInstOpcode,
                                    const TargetRegisterClass *RC,
                                    unsigned Op0, bool Op0IsKill,
                                    unsigned Op1, bool Op1IsKill) {
-  unsigned ResultReg = createResultReg(RC);
   const MCInstrDesc &II = TII.get(MachineInstOpcode);
 
+  unsigned ResultReg = createResultReg(RC);
+  Op0 = constrainOperandRegClass(II, Op0, II.getNumDefs());
+  Op1 = constrainOperandRegClass(II, Op1, II.getNumDefs() + 1);
+
   if (II.getNumDefs() >= 1)
     BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, II, ResultReg)
       .addReg(Op0, Op0IsKill * RegState::Kill)
@@ -1258,9 +1280,13 @@ unsigned FastISel::FastEmitInst_rrr(unsigned MachineInstOpcode,
                                    unsigned Op0, bool Op0IsKill,
                                    unsigned Op1, bool Op1IsKill,
                                    unsigned Op2, bool Op2IsKill) {
-  unsigned ResultReg = createResultReg(RC);
   const MCInstrDesc &II = TII.get(MachineInstOpcode);
 
+  unsigned ResultReg = createResultReg(RC);
+  Op0 = constrainOperandRegClass(II, Op0, II.getNumDefs());
+  Op1 = constrainOperandRegClass(II, Op1, II.getNumDefs() + 1);
+  Op2 = constrainOperandRegClass(II, Op2, II.getNumDefs() + 2);
+
   if (II.getNumDefs() >= 1)
     BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, II, ResultReg)
       .addReg(Op0, Op0IsKill * RegState::Kill)
@@ -1281,9 +1307,12 @@ unsigned FastISel::FastEmitInst_ri(unsigned MachineInstOpcode,
                                    const TargetRegisterClass *RC,
                                    unsigned Op0, bool Op0IsKill,
                                    uint64_t Imm) {
-  unsigned ResultReg = createResultReg(RC);
   const MCInstrDesc &II = TII.get(MachineInstOpcode);
 
+  unsigned ResultReg = createResultReg(RC);
+  RC = TII.getRegClass(II, II.getNumDefs(), &TRI, *FuncInfo.MF);
+  MRI.constrainRegClass(Op0, RC);
+
   if (II.getNumDefs() >= 1)
     BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, II, ResultReg)
       .addReg(Op0, Op0IsKill * RegState::Kill)
@@ -1302,9 +1331,11 @@ unsigned FastISel::FastEmitInst_rii(unsigned MachineInstOpcode,
                                    const TargetRegisterClass *RC,
                                    unsigned Op0, bool Op0IsKill,
                                    uint64_t Imm1, uint64_t Imm2) {
-  unsigned ResultReg = createResultReg(RC);
   const MCInstrDesc &II = TII.get(MachineInstOpcode);
 
+  unsigned ResultReg = createResultReg(RC);
+  Op0 = constrainOperandRegClass(II, Op0, II.getNumDefs());
+
   if (II.getNumDefs() >= 1)
     BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, II, ResultReg)
       .addReg(Op0, Op0IsKill * RegState::Kill)
@@ -1325,9 +1356,11 @@ unsigned FastISel::FastEmitInst_rf(unsigned MachineInstOpcode,
                                    const TargetRegisterClass *RC,
                                    unsigned Op0, bool Op0IsKill,
                                    const ConstantFP *FPImm) {
-  unsigned ResultReg = createResultReg(RC);
   const MCInstrDesc &II = TII.get(MachineInstOpcode);
 
+  unsigned ResultReg = createResultReg(RC);
+  Op0 = constrainOperandRegClass(II, Op0, II.getNumDefs());
+
   if (II.getNumDefs() >= 1)
     BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, II, ResultReg)
       .addReg(Op0, Op0IsKill * RegState::Kill)
@@ -1347,9 +1380,12 @@ unsigned FastISel::FastEmitInst_rri(unsigned MachineInstOpcode,
                                     unsigned Op0, bool Op0IsKill,
                                     unsigned Op1, bool Op1IsKill,
                                     uint64_t Imm) {
-  unsigned ResultReg = createResultReg(RC);
   const MCInstrDesc &II = TII.get(MachineInstOpcode);
 
+  unsigned ResultReg = createResultReg(RC);
+  Op0 = constrainOperandRegClass(II, Op0, II.getNumDefs());
+  Op1 = constrainOperandRegClass(II, Op1, II.getNumDefs() + 1);
+
   if (II.getNumDefs() >= 1)
     BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, II, ResultReg)
       .addReg(Op0, Op0IsKill * RegState::Kill)
@@ -1371,9 +1407,12 @@ unsigned FastISel::FastEmitInst_rrii(unsigned MachineInstOpcode,
                                      unsigned Op0, bool Op0IsKill,
                                      unsigned Op1, bool Op1IsKill,
                                      uint64_t Imm1, uint64_t Imm2) {
-  unsigned ResultReg = createResultReg(RC);
   const MCInstrDesc &II = TII.get(MachineInstOpcode);
 
+  unsigned ResultReg = createResultReg(RC);
+  Op0 = constrainOperandRegClass(II, Op0, II.getNumDefs());
+  Op1 = constrainOperandRegClass(II, Op1, II.getNumDefs() + 1);
+
   if (II.getNumDefs() >= 1)
     BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, II, ResultReg)
       .addReg(Op0, Op0IsKill * RegState::Kill)

lib/Target/ARM/ARMFastISel.cpp

@@ -166,8 +166,6 @@ class ARMFastISel final : public FastISel {
 
     // Utility routines.
   private:
-    unsigned constrainOperandRegClass(const MCInstrDesc &II, unsigned OpNum,
-                                      unsigned Op);
     bool isTypeLegal(Type *Ty, MVT &VT);
     bool isLoadTypeLegal(Type *Ty, MVT &VT);
     bool ARMEmitCmp(const Value *Src1Value, const Value *Src2Value,
@@ -283,23 +281,6 @@ ARMFastISel::AddOptionalDefs(const MachineInstrBuilder &MIB) {
   return MIB;
 }
 
-unsigned ARMFastISel::constrainOperandRegClass(const MCInstrDesc &II,
-                                               unsigned Op, unsigned OpNum) {
-  if (TargetRegisterInfo::isVirtualRegister(Op)) {
-    const TargetRegisterClass *RegClass =
-        TII.getRegClass(II, OpNum, &TRI, *FuncInfo.MF);
-    if (!MRI.constrainRegClass(Op, RegClass)) {
-      // If it's not legal to COPY between the register classes, something
-      // has gone very wrong before we got here.
-      unsigned NewOp = createResultReg(RegClass);
-      AddOptionalDefs(BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
-                              TII.get(TargetOpcode::COPY), NewOp).addReg(Op));
-      return NewOp;
-    }
-  }
-  return Op;
-}
-
 unsigned ARMFastISel::FastEmitInst_r(unsigned MachineInstOpcode,
                                      const TargetRegisterClass *RC,
                                      unsigned Op0, bool Op0IsKill) {