Subzero: Minor refactoring/additions in preparation for phi edge splitting.

src/IceTargetLowering.cpp

Index: src/IceTargetLowering.cpp
diff --git a/src/IceTargetLowering.cpp b/src/IceTargetLowering.cpp
index bcc629098bf94d13ef3012fb24900f6613dfa08b..ce7d3258bec60579d7e2884e93d579e039087240 100644
--- a/src/IceTargetLowering.cpp
+++ b/src/IceTargetLowering.cpp
@@ -54,6 +54,7 @@ void LoweringContext::init(CfgNode *N) {
 
 void LoweringContext::insert(Inst *Inst) {
   getNode()->getInsts().insert(Next, Inst);
+  LastInserted = Inst;
 }
 
 void LoweringContext::skipDeleted(InstList::iterator &I) const {
@@ -76,9 +77,8 @@ void LoweringContext::advanceBackward(InstList::iterator &I) const {
 }
 
 Inst *LoweringContext::getLastInserted() const {
-  InstList::iterator Cursor = Next;
-  advanceBackward(Cursor);
-  return *Cursor;
+  assert(LastInserted);
+  return LastInserted;
 }
 
 TargetLowering *TargetLowering::createLowering(TargetArch Target, Cfg *Func) {