Fix bug when atomic load is fused with an arith op (and not in the entry BB)

src/IceTargetLowering.cpp

 //===- subzero/src/IceTargetLowering.cpp - Basic lowering implementation --===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the skeleton of the TargetLowering class,
 // specifically invoking the appropriate lowering method for a given
 // instruction kind and driving global register allocation.  It also
 // implements the non-deleted instruction iteration in
 // LoweringContext.
 //
 //===----------------------------------------------------------------------===//
 
 #include "IceCfg.h" // setError()
 #include "IceCfgNode.h"
 #include "IceOperand.h"
 #include "IceRegAlloc.h"
 #include "IceTargetLowering.h"
 #include "IceTargetLoweringX8632.h"
 
 namespace Ice {
 
 void LoweringContext::init(CfgNode *N) {
   Node = N;
-  Cur = getNode()->getInsts().begin();
+  Begin = getNode()->getInsts().begin();
+  Cur = Begin;
   End = getNode()->getInsts().end();
   skipDeleted(Cur);
   Next = Cur;
-  advance(Next);
+  advanceForward(Next);
 }
 
 void LoweringContext::insert(Inst *Inst) {
   getNode()->getInsts().insert(Next, Inst);
   Inst->updateVars(getNode());
 }
 
 void LoweringContext::skipDeleted(InstList::iterator &I) const {
   while (I != End && (*I)->isDeleted())
     ++I;
 }
 
-void LoweringContext::advance(InstList::iterator &I) const {
+void LoweringContext::advanceForward(InstList::iterator &I) const {
   if (I != End) {
     ++I;
     skipDeleted(I);
   }
 }
 
+void LoweringContext::advanceBackward(InstList::iterator &I) const {
+  assert(I != Begin);
+  do {
+    --I;
+  } while (I != Begin && (*I)->isDeleted());
+}
+
+Inst *LoweringContext::getLastInserted() const {
+  InstList::iterator Cursor = Next;
+  advanceBackward(Cursor);
+  return *Cursor;
+}
+
 TargetLowering *TargetLowering::createLowering(TargetArch Target, Cfg *Func) {
   // These statements can be #ifdef'd to specialize the code generator
   // to a subset of the available targets.  TODO: use CRTP.
   if (Target == Target_X8632)
     return TargetX8632::create(Func);
 #if 0
   if (Target == Target_X8664)
     return IceTargetX8664::create(Func);
   if (Target == Target_ARM32)
     return IceTargetARM32::create(Func);
@@ skipping 131 matching lines @@
   if (Target == Target_ARM64)
     return IceTargetGlobalInitARM64::create(Ctx);
 #endif
   llvm_unreachable("Unsupported target");
   return NULL;
 }
 
 TargetGlobalInitLowering::~TargetGlobalInitLowering() {}
 
 } // end of namespace Ice