Linear Scan RA bug: avoid dst/src overlap for define only and use only variables

For define only and use only variables, since the live ranges are not overlap, linear scan RA may allow dst and src use same register. Extend liverange of dst 1 to create liverange overlap and avoid same register assigned.

Author: bcheng0127

visa/LinearScanRA.cpp

@@ -1165,7 +1165,11 @@ void LinearScanRA::setDstReferences(
     if (lr->getFirstRef(startIdx) == NULL && startIdx == 0) {
       lr->setFirstRef(curInst, curInst->getLexicalId() * 2);
     }
-    lr->setLastRef(curInst, curInst->getLexicalId() * 2);
+
+    // For dst, we set the last ref = lexcial_ID * 2 + 1.
+    // So that the dst will not be released immediately if it's defined only.
+    // This is to handle some special workload. Such as for LIT test
+    lr->setLastRef(curInst, curInst->getLexicalId() * 2 + 1);
   } else if (dcl->getRegVar()
                  ->getPhyReg()
                  ->isGreg()) // Assigned already and is GRF
@@ -1184,7 +1188,9 @@ void LinearScanRA::setDstReferences(
     if (lr->getFirstRef(startIdx) == NULL && startIdx == 0) {
       lr->setFirstRef(curInst, curInst->getLexicalId() * 2);
     }
-    lr->setLastRef(curInst, curInst->getLexicalId() * 2);
+    // For dst, we set the last ref = lexcial_ID * 2 + 1.
+    // So that the dst will not be released immediately if it's defined only.
+    lr->setLastRef(curInst, curInst->getLexicalId() * 2 + 1);
   }
 
   if (lr->isEOT() && std::find(eotLiveIntervals.begin(), eotLiveIntervals.end(),
@@ -1281,7 +1287,10 @@ void LinearScanRA::generateInputIntervals(
   unsigned int idx = regNum * builder.numEltPerGRF<Type_UW>() +
                      (regOff * topdcl->getElemSize()) / G4_WSIZE +
                      topdcl->getWordSize() - 1;
-
+  //Variable size may be larger than occupied GRF
+  if (idx > (kernel.getNumRegTotal() * builder.numEltPerGRF<Type_UW>() - 1)) {
+    idx = kernel.getNumRegTotal() * builder.numEltPerGRF<Type_UW>() - 1;
+  }
   unsigned int numWords = topdcl->getWordSize();
   for (int i = numWords - 1; i >= 0; --i, --idx) {
     if ((inputRegLastRef[idx] == UINT_MAX || inputRegLastRef[idx] < instID) &&