diff --git a/llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp b/llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp
--- a/llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp
@@ -647,29 +647,6 @@
   return CurDAG->getMachineNode(TargetOpcode::REG_SEQUENCE, DL, VT, Ops);
 }
 
-static unsigned selectSGPRVectorRegClassID(unsigned NumVectorElts) {
-  switch (NumVectorElts) {
-  case 1:
-    return AMDGPU::SReg_32RegClassID;
-  case 2:
-    return AMDGPU::SReg_64RegClassID;
-  case 3:
-    return AMDGPU::SGPR_96RegClassID;
-  case 4:
-    return AMDGPU::SGPR_128RegClassID;
-  case 5:
-    return AMDGPU::SGPR_160RegClassID;
-  case 8:
-    return AMDGPU::SReg_256RegClassID;
-  case 16:
-    return AMDGPU::SReg_512RegClassID;
-  case 32:
-    return AMDGPU::SReg_1024RegClassID;
-  }
-
-  llvm_unreachable("invalid vector size");
-}
-
 void AMDGPUDAGToDAGISel::SelectBuildVector(SDNode *N, unsigned RegClassID) {
   EVT VT = N->getValueType(0);
   unsigned NumVectorElts = VT.getVectorNumElements();
@@ -797,7 +774,8 @@
     }
 
     assert(VT.getVectorElementType().bitsEq(MVT::i32));
-    unsigned RegClassID = selectSGPRVectorRegClassID(NumVectorElts);
+    unsigned RegClassID =
+        SIRegisterInfo::getSGPRClassForBitWidth(NumVectorElts * 32)->getID();
     SelectBuildVector(N, RegClassID);
     return;
   }
diff --git a/llvm/lib/Target/AMDGPU/SIRegisterInfo.h b/llvm/lib/Target/AMDGPU/SIRegisterInfo.h
--- a/llvm/lib/Target/AMDGPU/SIRegisterInfo.h
+++ b/llvm/lib/Target/AMDGPU/SIRegisterInfo.h
@@ -116,6 +116,10 @@
     return getEncodingValue(Reg) & 0xff;
   }
 
+  static const TargetRegisterClass *getVGPRClassForBitWidth(unsigned BitWidth);
+  static const TargetRegisterClass *getAGPRClassForBitWidth(unsigned BitWidth);
+  static const TargetRegisterClass *getSGPRClassForBitWidth(unsigned BitWidth);
+
   /// Return the 'base' register class for this register.
   /// e.g. SGPR0 => SReg_32, VGPR => VGPR_32 SGPR0_SGPR1 -> SReg_32, etc.
   const TargetRegisterClass *getPhysRegClass(MCRegister Reg) const;
diff --git a/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp b/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
--- a/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
@@ -1274,7 +1274,8 @@
   return AMDGPUInstPrinter::getRegisterName(Reg);
 }
 
-static const TargetRegisterClass *getVGPRClassForBitWidth(unsigned BitWidth) {
+const TargetRegisterClass *
+SIRegisterInfo::getVGPRClassForBitWidth(unsigned BitWidth) {
   switch (BitWidth) {
   case 1:
     return &AMDGPU::VReg_1RegClass;
@@ -1301,7 +1302,8 @@
   }
 }
 
-static const TargetRegisterClass *getAGPRClassForBitWidth(unsigned BitWidth) {
+const TargetRegisterClass *
+SIRegisterInfo::getAGPRClassForBitWidth(unsigned BitWidth) {
   switch (BitWidth) {
   case 32:
     return &AMDGPU::AGPR_32RegClass;
@@ -1318,7 +1320,8 @@
   }
 }
 
-static const TargetRegisterClass *getSGPRClassForBitWidth(unsigned BitWidth) {
+const TargetRegisterClass *
+SIRegisterInfo::getSGPRClassForBitWidth(unsigned BitWidth) {
   switch (BitWidth) {
   case 16:
     return &AMDGPU::SGPR_LO16RegClass;