[GISel] Use SmallVector::append instead of copying one element at a time. (#119321)

Author: topperc

llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp

@@ -182,9 +182,8 @@ void LegalizerHelper::insertParts(Register DstReg,
   // Merge sub-vectors with different number of elements and insert into DstReg.
   if (ResultTy.isVector()) {
     assert(LeftoverRegs.size() == 1 && "Expected one leftover register");
-    SmallVector<Register, 8> AllRegs;
-    for (auto Reg : concat<const Register>(PartRegs, LeftoverRegs))
-      AllRegs.push_back(Reg);
+    SmallVector<Register, 8> AllRegs(PartRegs.begin(), PartRegs.end());
+    AllRegs.append(LeftoverRegs.begin(), LeftoverRegs.end());
     return mergeMixedSubvectors(DstReg, AllRegs);
   }
 
@@ -6397,10 +6396,8 @@ LegalizerHelper::narrowScalarAddSub(MachineInstr &MI, unsigned TypeIdx,
                MRI);
 
   int NarrowParts = Src1Regs.size();
-  for (int I = 0, E = Src1Left.size(); I != E; ++I) {
-    Src1Regs.push_back(Src1Left[I]);
-    Src2Regs.push_back(Src2Left[I]);
-  }
+  Src1Regs.append(Src1Left);
+  Src2Regs.append(Src2Left);
   DstRegs.reserve(Src1Regs.size());
 
   for (int i = 0, e = Src1Regs.size(); i != e; ++i) {
@@ -6572,8 +6569,7 @@ LegalizerHelper::narrowScalarInsert(MachineInstr &MI, unsigned TypeIdx,
   extractParts(MI.getOperand(1).getReg(), RegTy, NarrowTy, LeftoverTy, SrcRegs,
                LeftoverRegs, MIRBuilder, MRI);
 
-  for (Register Reg : LeftoverRegs)
-    SrcRegs.push_back(Reg);
+  SrcRegs.append(LeftoverRegs);
 
   uint64_t NarrowSize = NarrowTy.getSizeInBits();
   Register OpReg = MI.getOperand(2).getReg();