[Mips] Use a range-based for loop (NFC) (#106004)

Author: kazutakahirata

llvm/lib/Target/Mips/MipsConstantIslandPass.cpp

@@ -1631,28 +1631,26 @@ MipsConstantIslands::fixupConditionalBr(ImmBranch &Br) {
 
 void MipsConstantIslands::prescanForConstants() {
   for (MachineBasicBlock &B : *MF) {
-    for (MachineBasicBlock::instr_iterator I = B.instr_begin(),
-                                           EB = B.instr_end();
-         I != EB; ++I) {
-      switch(I->getDesc().getOpcode()) {
+    for (MachineInstr &MI : B) {
+      switch (MI.getDesc().getOpcode()) {
       case Mips::LwConstant32: {
         PrescannedForConstants = true;
-        LLVM_DEBUG(dbgs() << "constant island constant " << *I << "\n");
-        LLVM_DEBUG(dbgs() << "num operands " << I->getNumOperands() << "\n");
-        MachineOperand &Literal = I->getOperand(1);
+        LLVM_DEBUG(dbgs() << "constant island constant " << MI << "\n");
+        LLVM_DEBUG(dbgs() << "num operands " << MI.getNumOperands() << "\n");
+        MachineOperand &Literal = MI.getOperand(1);
         if (Literal.isImm()) {
           int64_t V = Literal.getImm();
           LLVM_DEBUG(dbgs() << "literal " << V << "\n");
           Type *Int32Ty = Type::getInt32Ty(MF->getFunction().getContext());
           const Constant *C = ConstantInt::get(Int32Ty, V);
           unsigned index = MCP->getConstantPoolIndex(C, Align(4));
-          I->getOperand(2).ChangeToImmediate(index);
-          LLVM_DEBUG(dbgs() << "constant island constant " << *I << "\n");
-          I->setDesc(TII->get(Mips::LwRxPcTcp16));
-          I->removeOperand(1);
-          I->removeOperand(1);
-          I->addOperand(MachineOperand::CreateCPI(index, 0));
-          I->addOperand(MachineOperand::CreateImm(4));
+          MI.getOperand(2).ChangeToImmediate(index);
+          LLVM_DEBUG(dbgs() << "constant island constant " << MI << "\n");
+          MI.setDesc(TII->get(Mips::LwRxPcTcp16));
+          MI.removeOperand(1);
+          MI.removeOperand(1);
+          MI.addOperand(MachineOperand::CreateCPI(index, 0));
+          MI.addOperand(MachineOperand::CreateImm(4));
         }
         break;
       }