[Autobackout][FunctionalRegression]Revert of change: 7f12958: Enable merging allocas for raytracing

Enable merging allocas for raytracing

Author: sys-igc

IGC/common/igc_flags.h

@@ -987,7 +987,7 @@ DECLARE_IGC_GROUP("Raytracing Options")
     DECLARE_IGC_REGKEY(bool, DisableRTStackOpts, false, "Disable some optimizations that minimize reads/writes to the RTStack", true)
     DECLARE_IGC_REGKEY(bool, DisablePrepareLoadsStores, false, "Disable preparation for MemOpt", true)
     DECLARE_IGC_REGKEY(bool, DisableRayTracingConstantCoalescing, false, "Disable coalescing", true)
-    DECLARE_IGC_REGKEY(bool, DisableMergeAllocas, false, "Do not merge allocas prior to SplitAsyncPass", false)
+    DECLARE_IGC_REGKEY(bool, DisableMergeAllocas, true, "Do not merge allocas prior to SplitAsyncPass", false)
     DECLARE_IGC_REGKEY(bool, DisableMergeAllocasPrivateMemory, false, "Do not merge allocas prior to PrivateMemoryResolution", false)
     DECLARE_IGC_REGKEY(bool, DisableMergingOfMultipleAllocasWithOffset, false, "Do not merge multiple smaller allocas under one larger one with different offsets.", false)
     DECLARE_IGC_REGKEY(DWORD, RayTracingConstantCoalescingMinBlockSize, 4, "Set the minimum load size in # OWords = [1,2,4,8,16].", true)