Revert "Re-enable selective scalarization"

---------------------------

(cherry picked from commit 5f9ed8a)

Author: AnBodrova

IGC/Compiler/Optimizer/Scalarizer.h

@@ -274,12 +274,11 @@ namespace IGC
 
 } // namespace IGC
 
-/// @brief By default (no argument given to this function), selective scalarization is controlled
-/// by the `EnableSelectiveScalarizer` regkey.
+/// @brief By default (no argument given to this function), selective scalarization is off.
 /// Selective scalarization keeps some instructions vectorized, if the vector is used as the whole entity.
 /// The pass builds a web of instructions protected from scalarization.
 /// The ending legs of the web consist of vectorial instructions such as insert and extract elements,
 /// vector shuffles, GenISA intrinsics and function calls.
 /// The vectorial instructions inside the web consist of bitcasts and PHI nodes.
 extern "C" llvm::FunctionPass *createScalarizerPass(
-    IGC::SelectiveScalarizer selectiveMode = IGC::SelectiveScalarizer::Auto);
+    IGC::SelectiveScalarizer selectiveMode = IGC::SelectiveScalarizer::Off);

IGC/common/igc_flags.h

@@ -485,7 +485,7 @@ DECLARE_IGC_REGKEY(bool,  DisableMergeStore,            false, "[temp]If EnableL
 DECLARE_IGC_REGKEY(DWORD,MaxLiveOutThreshold,           0,     "Max LiveOut Threshold in MemOpt2", false)
 DECLARE_IGC_REGKEY(bool, DisableScalarAtomics,          false, "Disable the Scalar Atomics optimization", false)
 DECLARE_IGC_REGKEY(bool, EnableScalarTypedAtomics,      true, "Enable the Scalar Typed Atomics optimization", false)
-DECLARE_IGC_REGKEY(bool, EnableSelectiveScalarizer,     true,  "Enable selective scalarizer on GPGPU path", true)
+DECLARE_IGC_REGKEY(bool, EnableSelectiveScalarizer,     false,  "enable selective scalarizer on GPGPU path", true)
 DECLARE_IGC_REGKEY(bool, HoistPSConstBufferValues,      true,  "Hoists up down converts for contant buffer accesses, so they an be vectorized more easily.", false)
 DECLARE_IGC_REGKEY(bool, EnableSingleVertexDispatch,    false, "Vertex Shader Single Patch Dispatch Regkey", false)
 DECLARE_IGC_REGKEY(bool, allowLICM,                     true,  "Enable LICM in IGC.", true)