Update DispatchGPGPUWalkerAlongYFirst lookup

Author: iwwu

IGC/Compiler/CISACodeGen/ComputeShaderCodeGen.cpp

@@ -402,8 +402,10 @@ namespace IGC
         const ComputeShaderContext* pCtx =
             static_cast<const ComputeShaderContext*>(GetContext());
 
-        if (IGC_IS_FLAG_ENABLED(DispatchGPGPUWalkerAlongYFirst) &&
-            (m_num2DAccesses > m_num1DAccesses) &&
+        // Assume DispatchGPGPUWalkerAlongYFirst is on here unless off explicitly
+        if (IGC_GET_FLAG_VALUE(DispatchGPGPUWalkerAlongYFirst) == 0)
+            m_dispatchAlongY = false;
+        else if ((m_num2DAccesses > m_num1DAccesses) &&
             !pCtx->getModuleMetaData()->csInfo.disableLocalIdOrderOptimizations &&
             GetContext()->m_DriverInfo.SupportsDispatchGPGPUWalkerAlongYFirst())
         {

IGC/common/igc_flags.def

@@ -385,7 +385,7 @@ DECLARE_IGC_REGKEY(bool, disableVarSplit,               false, "disable variable
 DECLARE_IGC_REGKEY(bool, disableRemat,                  false, "disable re-materialization", false)
 DECLARE_IGC_REGKEY(bool, EnableDisableMidThreadPreemptionOpt, true, "Disable mid thread preemption", false)
 DECLARE_IGC_REGKEY(DWORD, MidThreadPreemptionDisableThreshold, 600, "Threshold to disable mid thread preemption", false)
-DECLARE_IGC_REGKEY(bool, DispatchGPGPUWalkerAlongYFirst, true, "dispatch GPGPU walker along Y first", false)
+DECLARE_IGC_REGKEY(DWORD, DispatchGPGPUWalkerAlongYFirst, 2,  "1 = Dispatch GPGPU walker along Y first, 0 = No SW Y-walk Optimization, 2 = use platform default setting", false)
 DECLARE_IGC_REGKEY(bool, SetMaxPreRASchedulerRegPressureThreshold, false,  "set Max PreRA Scheduler Threshold", false)
 DECLARE_IGC_REGKEY(bool, LimitConstantBuffersPushed,    true, "Limit max number of CBs pushed when SupportIndirectConstantBuffer is true", false)
 DECLARE_IGC_REGKEY(DWORD, MaxPreRASchedulerRegPressureThreshold, 60,  "Max PreRA Scheduler Threshold", false)