AMDGPU: Remove unnecessary AGPR legalize logic (llvm#159491)

The manual legalizeOperands code only need to consider cases that
require full instruction context to know if the operand is legal.
This does not need to handle basic operand register class constraints.

Author: arsenm

llvm/lib/Target/AMDGPU/SIInstrInfo.cpp

@@ -6371,13 +6371,6 @@ void SIInstrInfo::legalizeOperandsVOP2(MachineRegisterInfo &MRI,
     return;
   }
 
-  // No VOP2 instructions support AGPRs.
-  if (Src0.isReg() && RI.isAGPR(MRI, Src0.getReg()))
-    legalizeOpWithMove(MI, Src0Idx);
-
-  if (Src1.isReg() && RI.isAGPR(MRI, Src1.getReg()))
-    legalizeOpWithMove(MI, Src1Idx);
-
   // Special case: V_FMAC_F32 and V_FMAC_F16 have src2.
   if (Opc == AMDGPU::V_FMAC_F32_e32 || Opc == AMDGPU::V_FMAC_F16_e32) {
     int Src2Idx = AMDGPU::getNamedOperandIdx(Opc, AMDGPU::OpName::src2);
@@ -6518,12 +6511,6 @@ void SIInstrInfo::legalizeOperandsVOP3(MachineRegisterInfo &MRI,
       continue;
     }
 
-    if (RI.hasAGPRs(RI.getRegClassForReg(MRI, MO.getReg())) &&
-        !isOperandLegal(MI, Idx, &MO)) {
-      legalizeOpWithMove(MI, Idx);
-      continue;
-    }
-
     if (!RI.isSGPRClass(RI.getRegClassForReg(MRI, MO.getReg())))
       continue; // VGPRs are legal