Revert it until the build is green. Need to have a

clean build for testing purpose

Change-Id: I4a4adc072e3565848aa263da8740f5b1f036bee5

Author: jgu222

IGC/common/igc_flags.def

@@ -69,7 +69,7 @@ DECLARE_IGC_REGKEY(DWORD, LoopSinkThresholdDelta,       50,  "Do loop sink If th
 DECLARE_IGC_REGKEY(bool, DisableCodeHoisting,           false, "Setting this to 1/true adds a compiler switch to disable code-hoisting")
 DECLARE_IGC_REGKEY(bool, DisableDeSSA,                  false, "Setting this to 1/true adds a compiler switch to disable optimized De-SSA")
 DECLARE_IGC_REGKEY(bool, EnableDeSSAWA,                 true,  "[tmp]Keep some piece of code to avoid perf regression")
-DECLARE_IGC_REGKEY(DWORD, EnableDeSSAAlias,             1, "[tmp]Enable adding alias feature to DeSSA (using PrefCCMap, not InsEltMap")
+DECLARE_IGC_REGKEY(DWORD, EnableDeSSAAlias,             0, "[tmp]Enable adding alias feature to DeSSA (using PrefCCMap, not InsEltMap")
 DECLARE_IGC_REGKEY(bool, EnableDeSSAMemberRootValue,    true, "[tmp]When this is set, root value of dessa is its real member value; otherwise, the root value is just id for a CC.")
 DECLARE_IGC_REGKEY(bool, DisablePayloadCoalescing,      false, "Setting this to 1/true adds a compiler switch to disable payload coalescing optimization for all types")
 DECLARE_IGC_REGKEY(bool, DisablePayloadCoalescing_RT,   false, "Setting this to 1/true adds a compiler switch to disable payload coalescing optimization for RT only")