Enable copy propagation of operands with send instructions

IGC currently does not allow copy propagation of operands between mov
and send instructions. Enabling this can result in performance
improvement through reduction of instruction count; instruction count is
reduced through elimination of mov instructions.

Author: anikaushik

visa/G4_IR.cpp

@@ -1866,11 +1866,29 @@ bool G4_INST::canPropagateTo(G4_INST *useInst, Gen4_Operand_Number opndNum,
     }
   }
 
-  // The following are copied from local dataflow analysis.
-  // TODO: re-examine..
-  if (((opndNum == Opnd_src0 && useInst->isSend()) && !statelessAddr) ||
-      (opndNum == Opnd_src1 && useInst->isSplitSend())) {
-    return false;
+  // allow copy propagation with send instruction under following conditions
+  // 1. src operand is not an immediate value
+  // 2. src and dst have same type and # of elements
+  // 3. src is grf aligned
+  if ((opndNum == Opnd_src0 && useInst->isSend()) ||
+          (opndNum == Opnd_src1 && useInst->isSplitSend())) {
+
+    // check platform gen; apply this optimization only for Gen11 and beyond
+    // due to HW restriction where src0 and src1 operands must not overlap
+    if (getBuilder().getPlatformGeneration() < PlatformGen::GEN11) {
+      return false;
+    }
+    if (src->isImm()) return false;
+    if (src->getTopDcl()->getNumElems() != dst->getTopDcl()->getNumElems())
+        return false;
+    if (MT != G4_INST::Copy) return false;
+    // EOT messages have specific constraints on register range for src0, src1
+    // for now, do not do copy propaation on src0, src1 for eot sends
+    if (useInst->isEOT()) return false;
+    // Check alignment last as isOpndAligned will change the alignment
+    if (!getBuilder().tryToAlignOperand(src, getBuilder().numEltPerGRF<Type_UB>())) {
+        return false;
+    }
   }
 
   auto isFloatPseudoMAD = [](G4_INST *inst) {