Allow spills to spill again in fail safe iteration

Due to constraints, spilled variables may spill again in fail safe
iteration. This generates extra code but it guarantees completion of
compilation.

Author: pratikashar

visa/G4_Register.h

@@ -393,10 +393,7 @@ class G4_RegVarTmp : public G4_RegVar {
 
 public:
   G4_RegVarTmp(G4_Declare *d, G4_RegVar *base)
-      : G4_RegVar(d, RegVarType::GRFSpillTmp), baseRegVar(base) {
-    vASSERT(base->isRegVarTransient() == false);
-    vASSERT(base == base->getBaseRegVar());
-  }
+      : G4_RegVar(d, RegVarType::GRFSpillTmp), baseRegVar(base) {}
   void *operator new(size_t sz, Mem_Manager &m) { return m.alloc(sz); }
 
   G4_RegVar *getBaseRegVar() { return baseRegVar; }

visa/GraphColor.cpp

@@ -6566,7 +6566,16 @@ void GraphColor::computeSpillCosts(bool useSplitLLRHeuristic, const RPE *rpe) {
               lrs[i]->getVar()->isSpilled() == false) ||
              dcl == gra.getOldFPDcl() ||
              (!builder.canReadR0() && dcl == builder.getBuiltinR0())) {
-      lrs[i]->setSpillCost(MAXSPILLCOST);
+      if (failSafeIter) {
+        // Allow spills to again spill in fail safe iteration in order to
+        // guarantee compilation succeeds.
+        if (lrs[i]->getVar()->isRegVarTransient() == true ||
+            lrs[i]->getVar()->isRegVarTmp() == true) {
+          lrs[i]->setSpillCost(0.99f * MAXSPILLCOST);
+        } else
+          lrs[i]->setSpillCost(MAXSPILLCOST);
+      } else
+        lrs[i]->setSpillCost(MAXSPILLCOST);
     } else if (dcl->isDoNotSpill()) {
       lrs[i]->setSpillCost(MAXSPILLCOST);
     }
@@ -6763,7 +6772,7 @@ void GraphColor::removeConstrained() {
 void GraphColor::determineColorOrdering() {
   numColor = 0;
   if (liveAnalysis.livenessClass(G4_GRF))
-    numColor = totalGRFRegCount - reserveSpillGRFCount;
+    numColor = totalGRFRegCount;
   else if (liveAnalysis.livenessClass(G4_ADDRESS))
     numColor = builder.getNumAddrRegisters();
   else if (liveAnalysis.livenessClass(G4_FLAG))
@@ -11201,6 +11210,7 @@ bool GlobalRA::setupFailSafeIfNeeded(bool fastCompile, bool hasStackCall,
       }
     }
   }
+
   return reserveSpillReg;
 }
 

visa/RADebug.cpp

@@ -1037,6 +1037,10 @@ bool Interference::dumpIntf(const char *s) const {
         if (interfereBetween(i, j)) {
           std::cout << "\t";
           lrs[j]->getVar()->emit(std::cout);
+          if (lrs[j]->getPhyReg()) {
+            std::cout << "(r" << lrs[j]->getPhyReg()->asGreg()->getRegNum()
+                      << ")\n";
+          }
         }
       }
       std::cout << "\n";

visa/SpillManagerGMRF.cpp

@@ -293,8 +293,11 @@ bool SpillManagerGRF::shouldSpillRegister(G4_RegVar *regVar) const {
           : regVar;
   if (actualRegVar->getId() == UNDEFINED_VAL)
     return false;
-  else if (regVar->isRegVarTransient() || regVar->isRegVarTmp())
-    return false;
+  else if (regVar->isRegVarTransient() || regVar->isRegVarTmp()) {
+    if (!failSafeSpill_)
+      return false;
+    return true;
+  }
 #ifndef ADDRESS_SENSITIVE_SPILLS_IMPLEMENTED
   else if (lvInfo_->isAddressSensitive(regVar->getId()))
     return false;