Fix bug where reRA pass obliterated gtpin data

structure fields.

Restore next free scratch slot field of gtpin info which was clobbered
by reRA pass.

Author: pratikashar

visa/G4_Kernel.cpp

@@ -522,6 +522,11 @@ void gtPinData::setScratchNextFree(unsigned next) {
     nextScratchFree = ((next + kernel.numEltPerGRF<Type_UB>() - 1) / kernel.numEltPerGRF<Type_UB>()) * kernel.numEltPerGRF<Type_UB>();
 }
 
+unsigned int gtPinData::getScratchNextFree() const
+{
+    return nextScratchFree;
+}
+
 uint32_t gtPinData::getNumBytesScratchUse() const
 {
     if (gtpin_init)

visa/G4_Kernel.hpp

@@ -106,6 +106,7 @@ class gtPinData
     void* getGTPinInfoBuffer(unsigned &bufferSize);
 
     void setScratchNextFree(unsigned next);
+    unsigned int getScratchNextFree() const;
 
     uint32_t getNumBytesScratchUse() const;
 

visa/Optimizer.cpp

@@ -1870,6 +1870,7 @@ void Optimizer::reRAPostSchedule()
     if (builder.getIsPayload())
         return;
     auto freeGRFsBeforeReRA = gtpin->getNumFreeGlobalRegs();
+    auto nextScratchFreeBeforeReRA = gtpin->getScratchNextFree();
 
     storeGRFAssignments(kernel.Declares, assignments);
     // This pass is run for gtpin since they need re-allocation after
@@ -1944,6 +1945,7 @@ void Optimizer::reRAPostSchedule()
         computeGlobalFreeGRFs(kernel);
     }
 
+    gtpin->setScratchNextFree(nextScratchFreeBeforeReRA);
     *builder.getJitInfo() = finalizerInfo;
 }