[Autobackout][FuncReg]Revert of change: b1856f9

Remove Instruction Combining after Memory Opt. MemOpt may combine load/store instructions, while running InstCombine without IR lowering will change the alignment based on the new load/store value types.
HSD/Radar: n/a

Change-Id: I72f3f31848b14dd035744d52648604611d46d30a

Author: dlei6g

IGC/Compiler/CISACodeGen/ShaderCodeGen.cpp

@@ -474,11 +474,12 @@ namespace IGC
     mpm.add(CreatePrivateMemoryResolution());
 
     // Run MemOpt
-    bool doMemOpt = ctx.m_instrTypes.hasLoadStore && IGC_IS_FLAG_DISABLED(DisableMemOpt);
-    if (!isOptDisabled && doMemOpt) {
+    if (!isOptDisabled &&
+        ctx.m_instrTypes.hasLoadStore && IGC_IS_FLAG_DISABLED(DisableMemOpt)) {
         if (IGC_IS_FLAG_ENABLED(EnableAdvMemOpt))
           mpm.add(createAdvMemOptPass());
         mpm.add(createMemOptPass());
+        mpm.add(createIGCInstructionCombiningPass());
     }
 
     if (ctx.type == ShaderType::OPENCL_SHADER &&
@@ -529,7 +530,7 @@ namespace IGC
     if (!isOptDisabled)
     {
         // Optimize lower-level IR
-        if (!fastCompile || doMemOpt)
+        if (!fastCompile)
         {
             mpm.add(createIGCInstructionCombiningPass());
         }