Add option to set spill threshold for 256GRF.

Author: jfuentes

visa/G4_Kernel.cpp

@@ -2216,3 +2216,12 @@ bool GRFMode::hasLargerGRFSameThreads() const {
 
   return configs[currentMode].numThreads == configs[largerGrfIdx].numThreads;
 }
+
+// Get spill threshold for current GRF mode
+unsigned GRFMode::getSpillThreshold() const {
+  if (configs[currentMode].numGRF == 256 &&
+      options->getuInt32Option(vISA_SpillAllowed256GRF) > 0)
+    return options->getuInt32Option(vISA_SpillAllowed256GRF);
+
+  return options->getuInt32Option(vISA_SpillAllowed);
+}

visa/G4_Kernel.hpp

@@ -155,6 +155,7 @@ class GRFMode {
   unsigned setModeByRegPressure(unsigned maxRP, unsigned largestInputReg,
                                 bool forceGRFModedUp = false);
   bool hasLargerGRFSameThreads() const;
+  unsigned getSpillThreshold() const;
 
   unsigned getNumGRF() const { return configs[currentMode].numGRF; }
   unsigned getDefaultGRF() const { return configs[defaultMode].numGRF; }

visa/GraphColor.cpp

@@ -2152,7 +2152,7 @@ bool GlobalRA::canIncreaseGRF(unsigned spillSize, bool infCostSpilled) {
   //  - #GRFs selected and next larger one has same number of threads, or
   //  - Spill size is above threshold
   if ((infCostSpilled || kernel.grfMode.hasLargerGRFSameThreads() ||
-       spillSize >= kernel.getuInt32Option(vISA_SpillAllowed)) &&
+       spillSize >= kernel.grfMode.getSpillThreshold()) &&
       !didGRFIncrease) {
     if (kernel.updateKernelToLargerGRF()) {
       // GRF successfully increased

visa/include/VISAOptionsDefs.h

@@ -168,6 +168,12 @@ DEF_VISA_OPTION(
     "Spill size allowed without increasing GRF number in VRT."
     "0 means VRT will always bump up the GRF number to avoid spills",
     256)
+DEF_VISA_OPTION(vISA_SpillAllowed256GRF, ET_INT32, "-spillAllowed256GRF",
+                "USAGE: -spillAllowed256GRF <spillSize>.\n"
+                "Override spill threshold for 256GRF config. If shader has "
+                "spills < <spillSize>, #GRF is not bumped up. "
+                "0 means no override",
+                0)
 DEF_VISA_OPTION(vISA_ForceGRFModeUp, ET_INT32, "-forceGRFModeUp",
                 "USAGE: -forceGRFModeUp <k>.\n"
                 "Set the GRF mode k higher than the one selected by default"