Change the Spill Threshold (based on API)for SLM heuristic for better SIMD selection.

Change the Spill Threshold per API for SLM heuristic for better SIMD selection.

Author: ashwinikardile

IGC/Compiler/CISACodeGen/DriverInfo.hpp

@@ -304,6 +304,8 @@ namespace IGC
         // Determines whether the PAYLOAD_HEADER implicit arg must be present
         virtual bool RequirePayloadHeader() const { return true; }
 
+        virtual float getCSSpillThresholdSLM() const { return 12; }
+
 
 
     };

IGC/Compiler/CodeGenContext.cpp

@@ -506,8 +506,13 @@ namespace IGC
 
     float ComputeShaderContext::GetSpillThreshold() const
     {
-        float spillThresholdSLM =
-            float(IGC_GET_FLAG_VALUE(CSSpillThresholdSLM)) / 100.0f;
+        //CSSpillThresholdSLM is initialized as 0. If CSSpillThresholdSLM = 0, it is set to 12 as its default value, otherwise it is set to 9 for Dx12 API.
+
+        float spillThresholdSLM = 0;
+        spillThresholdSLM = m_DriverInfo.getCSSpillThresholdSLM();
+
+        if(IGC_IS_FLAG_ENABLED(CSSpillThresholdSLMOverride))
+            spillThresholdSLM = float(IGC_GET_FLAG_VALUE(CSSpillThresholdSLM)) / 100.0f;
         float spillThresholdNoSLM =
             float(IGC_GET_FLAG_VALUE(CSSpillThresholdNoSLM)) / 100.0f;
         return m_slmSize ? spillThresholdSLM : spillThresholdNoSLM;

IGC/common/igc_flags.h

@@ -319,7 +319,8 @@ DECLARE_IGC_REGKEY(bool, EnableSelectiveScalarizer,     false,  "enable selectiv
 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.", false)
-DECLARE_IGC_REGKEY(DWORD, CSSpillThresholdSLM,          12,    "Spill Threshold for CS SIMD16 with SLM", false)
+DECLARE_IGC_REGKEY(bool, CSSpillThresholdSLMOverride,   false, "Override for CSSpillThresholdSLM", false)
+DECLARE_IGC_REGKEY(DWORD, CSSpillThresholdSLM,          0,    "Spill Threshold for CS SIMD16 with SLM, use CSSpillThresholdSLMOverride along with this", false)
 DECLARE_IGC_REGKEY(DWORD, CSSpillThresholdNoSLM,        5,     "Spill Threshold for CS SIMD16 without SLM", false)
 DECLARE_IGC_REGKEY(DWORD, AllowedSpillRegCount,         0,     "Max allowed spill size without recompile", false)
 DECLARE_IGC_REGKEY(DWORD, LICMStatThreshold,            70,    "LICM stat threshold to avoid retry SIMD16 for CS", false)