Fix incorrect code movement in CMABI

replaceUsesWithinFunction incorrectly moved code trying to fix phi
issues that never arised. Remove fixing code as it really looks like
it should not be here at all:

1) breakConstantExprs is called before and it removes all
constantExprs from module;
2) only uses that are instructions are analyzed so it is impossible to
change global inside constexpr to alloca.

The only possible way to break things is to add another SCC pass
immediately before CMABI that will restore constexpr as CMABI breaks
them in doInitialization. Though, this should be fixed with redesign
of CMABI and doing all the work in "run" function.

Change-Id: I24ac5e3c8977977ac782e9a6c01ee238948b3d5d

Author: aus-intel

IGC/VectorCompiler/lib/GenXOpts/CMTrans/CMABI.cpp

@@ -482,42 +482,19 @@ bool CMABI::runOnSCC(CallGraphSCC &SCC) {
   return Changed;
 }
 
-// Sometimes we can get phi with GEP (or maybe some other inst) as an argument.
-// While GEP's arguments are constants, its OK as GEP is a constant to.
-// But when we replace constants with lokals, GEP becomes a normal instruction,
-// a normal instruction, that is placed before phi - wrong IR, we need to fix
-// it. Here it is fixed.
-static void fixPhiUseIssue(Instruction *Inst) {
-  auto PhiUse = cast<PHINode>(Inst->use_begin()->getUser());
-  auto InstOpNoInPhi = Inst->use_begin()->getOperandNo();
-  IGC_ASSERT(Inst->getParent() == PhiUse->getParent());
-  Inst->removeFromParent();
-  Inst->insertBefore(PhiUse->getIncomingBlock(InstOpNoInPhi)->getTerminator());
-}
-
 // Replace uses of global variables with the corresponding allocas with a
 // specified function.
-//
-// Returns vector of instructions with phi use, that should be later fixed.
-static std::vector<Instruction *>
+static void
 replaceUsesWithinFunction(SmallDenseMap<Value *, Value *> &GlobalsToReplace,
                           Function *F) {
-  std::vector<Instruction *> PhiUseIssueInsts;
   for (auto I = inst_begin(F), E = inst_end(F); I != E; ++I) {
     Instruction *Inst = &*I;
     for (unsigned i = 0, e = Inst->getNumOperands(); i < e; ++i) {
       auto Iter = GlobalsToReplace.find(Inst->getOperand(i));
       if (Iter != GlobalsToReplace.end())
         Inst->setOperand(i, Iter->second);
     }
-    if (Inst->getNumUses() == 1) {
-      auto PhiUse = dyn_cast<PHINode>(Inst->use_begin()->getUser());
-      if (PhiUse && Inst->getParent() == PhiUse->getParent()) {
-        PhiUseIssueInsts.push_back(Inst);
-      }
-    }
   }
-  return PhiUseIssueInsts;
 }
 
 // \brief Create allocas for globals directly used in this kernel and
@@ -544,11 +521,7 @@ void CMABI::LocalizeGlobals(LocalizationInfo &LI) {
   }
 
   // Replaces all globals uses within this function.
-  auto PhiUseIssueInsts = replaceUsesWithinFunction(GlobalsToReplace, Fn);
-
-  for (auto InstWithPhiUse : PhiUseIssueInsts) {
-    fixPhiUseIssue(InstWithPhiUse);
-  }
+  replaceUsesWithinFunction(GlobalsToReplace, Fn);
 }
 
 CallGraphNode *CMABI::ProcessNode(CallGraphNode *CGN) {