Subzero: Fix a build issue against LLVM trunk.

src/IceTargetLoweringMIPS32.cpp

Index: src/IceTargetLoweringMIPS32.cpp
diff --git a/src/IceTargetLoweringMIPS32.cpp b/src/IceTargetLoweringMIPS32.cpp
index 1104a493a109990d274d37abbbce7fab21cbe4f8..36650bdad05066182e43e0509a8c48bd0557769d 100644
--- a/src/IceTargetLoweringMIPS32.cpp
+++ b/src/IceTargetLoweringMIPS32.cpp
@@ -1296,7 +1296,7 @@ void TargetMIPS32::lowerArguments() {
     for (CfgNode *Node : Func->getNodes()) {
       for (Inst &Instr : Node->getInsts()) {
         if (llvm::isa<InstRet>(&Instr)) {
-          Context.setInsertPoint(Instr);
+          Context.setInsertPoint(instToIterator(&Instr));
           Context.insert<InstFakeUse>(ImplicitRetVec);
           break;
         }