[IGC vISA] Fix byte swizzle restriction on src0 in HWConformity

When fix byte swizzle restrictions, we split SIMD2 instruction to fix the illegal
operands to generate better codes. But if dst and src have overlap, we should avoid
splitting instruction, otherwise there will be a extra mov instructions inserted to
resolve the dst/src overlap which is not legalized.

Before fix:
   mov (2)   V42(0,14)<1>:w  V42(0,14)<2;1,0>:w
   =>
   mov (2)   TV(0,0)<1>      V42(0,14)<2;1,0>:w
   mov (1)   V42(0,14)<1>:w  TV(0,0)<0;1,0>:w
   mov (1)   V42(0,15)<1>:w  TV(0,1)<0;1,0>:w

After fix:
   mov (2)   V42(0,14)<1>:w  V42(0,14)<2;1,0>:w
   =>
   mov (2)   TV(0,28)<2>:w   V42(0,14)<2;1,0>:w
   mov (2)   V42(0,14)<1>:w  TV(0,28)<2;1,0>:w

Author: fangliu2020

visa/HWConformity.cpp

@@ -9106,9 +9106,31 @@ void HWConformity::fixByteXBarRestriction(INST_LIST_ITER it, G4_BB *bb) {
   }
 
   if (needFix) {
+
+    // split currently can't handle packed imm
+    // Also don't split if src and dst have overlap as it will introduce extra
+    // mov which could be illegal. If we further fix the extra illegal mov
+    // instruction, we will get worse codes compared to not splitting.
+    auto canDoSplit = [](G4_INST *inst, IR_Builder &builder) {
+      if (inst->getPredicate() || inst->getCondMod()) {
+        return false;
+      }
+      for (int i = 0, numSrc = inst->getNumSrc(); i < numSrc; ++i) {
+        auto ty = inst->getSrc(i)->getType();
+        if (IS_VINTTYPE(ty) || IS_VFTYPE(ty)) {
+          return false;
+        } else {
+          G4_CmpRelation rel =
+              inst->getDst()->compareOperand(inst->getSrc(i), builder);
+          if (rel != Rel_disjoint)
+            return false;
+        }
+      }
+      return true;
+    };
+
     if (inst->getExecSize() == g4::SIMD2 && allDirect &&
-        inst->getNumSrc() != 3 && !inst->getPredicate() &&
-        !inst->getCondModBase()) {
+        inst->getNumSrc() != 3 && canDoSplit(inst, builder)) {
       // just split the inst
       evenlySplitInst(it, bb);
       return;