[ARM] Correct SP/PC handling in t2MOVr

[john.brawn]

Summary

PC isn't allowed in the source operand of t2MOVr, so change the register class to one without PC. SP handling is slightly trickier and changes depending on if we're in ARMv8, so do that in checkTargetMatchPredicate.

[rengolin]

Good catch! LGTM.

llvm/trunk/lib/Target/ARM/ARMInstrThumb2.td

 } // hasSideEffects
 
 
 //===----------------------------------------------------------------------===//
 //  Move Instructions.
 //
 
 let hasSideEffects = 0 in
-def t2MOVr : T2sTwoReg<(outs GPRnopc:$Rd), (ins GPR:$Rm), IIC_iMOVr,
+def t2MOVr : T2sTwoReg<(outs GPRnopc:$Rd), (ins GPRnopc:$Rm), IIC_iMOVr,
                    "mov", ".w\t$Rd, $Rm", []>, Sched<[WriteALU]> {
   let Inst{31-27} = 0b11101;
   let Inst{26-25} = 0b01;
   let Inst{24-21} = 0b0010;
   let Inst{19-16} = 0b1111; // Rn
   let Inst{14-12} = 0b000;
   let Inst{7-4} = 0b0000;
 }
-def : t2InstAlias<"mov${p}.w $Rd, $Rm", (t2MOVr GPRnopc:$Rd, GPR:$Rm,
+def : t2InstAlias<"mov${p}.w $Rd, $Rm", (t2MOVr GPRnopc:$Rd, GPRnopc:$Rm,
                                                 pred:$p, zero_reg)>;
-def : t2InstAlias<"movs${p}.w $Rd, $Rm", (t2MOVr GPRnopc:$Rd, GPR:$Rm,
+def : t2InstAlias<"movs${p}.w $Rd, $Rm", (t2MOVr GPRnopc:$Rd, GPRnopc:$Rm,
                                                  pred:$p, CPSR)>;
-def : t2InstAlias<"movs${p} $Rd, $Rm", (t2MOVr GPRnopc:$Rd, GPR:$Rm,
+def : t2InstAlias<"movs${p} $Rd, $Rm", (t2MOVr GPRnopc:$Rd, GPRnopc:$Rm,
                                                pred:$p, CPSR)>;
 
 // AddedComplexity to ensure isel tries t2MOVi before t2MOVi16.
 let isReMaterializable = 1, isAsCheapAsAMove = 1, isMoveImm = 1,
     AddedComplexity = 1 in
 def t2MOVi : T2sOneRegImm<(outs rGPR:$Rd), (ins t2_so_imm:$imm), IIC_iMOVi,
                    "mov", ".w\t$Rd, $imm",
                    [(set rGPR:$Rd, t2_so_imm:$imm)]>, Sched<[WriteALU]> {

llvm/trunk/lib/Target/ARM/AsmParser/ARMAsmParser.cpp

if (Opc == ARM::tADDhirr && !hasV6MOps() &&
       return Match_RequiresThumb2;
     // Others only require ARMv6 or later.
     else if (Opc == ARM::tMOVr && !hasV6Ops() &&
              isARMLowRegister(Inst.getOperand(0).getReg()) &&
              isARMLowRegister(Inst.getOperand(1).getReg()))
       return Match_RequiresV6;
   }
 
+  // Before ARMv8 the rules for when SP is allowed in t2MOVr are more complex
+  // than the loop below can handle, so it uses the GPRnopc register class and
+  // we do SP handling here.
+  if (Opc == ARM::t2MOVr && !hasV8Ops())
+  {
+    // SP as both source and destination is not allowed
+    if (Inst.getOperand(0).getReg() == ARM::SP &&
+        Inst.getOperand(1).getReg() == ARM::SP)
+      return Match_RequiresV8;
+    // When flags-setting SP as either source or destination is not allowed
+    if (Inst.getOperand(4).getReg() == ARM::CPSR &&
+        (Inst.getOperand(0).getReg() == ARM::SP ||
+         Inst.getOperand(1).getReg() == ARM::SP))
+      return Match_RequiresV8;
+  }
+
   for (unsigned I = 0; I < MCID.NumOperands; ++I)
     if (MCID.OpInfo[I].RegClass == ARM::rGPRRegClassID) {
       // rGPRRegClass excludes PC, and also excluded SP before ARMv8
       if ((Inst.getOperand(I).getReg() == ARM::SP) && !hasV8Ops())
         return Match_RequiresV8;
       else if (Inst.getOperand(I).getReg() == ARM::PC)
         return Match_InvalidOperand;
     }