Handle 16-byte alignment correct for trivial and local RA.

Change-Id: Iffce10c718fe79d041aa0f9e2ae023438ac5e6de

Author: weiyu-chen

visa/G4Verifier.cpp

@@ -794,6 +794,18 @@ void G4Verifier::verifyOpnd(G4_Operand* opnd, G4_INST* inst)
                     }
                 }
             }
+
+            // if src0 is V/UV/VF imm, dst must be 16 byte aligned.
+            if (inst->opcode() == G4_mov && IS_VTYPE(inst->getSrc(0)->getType()))
+            {
+                auto dst = inst->getDst();
+                // should we assert if dst is not phyReg assigned?
+                bool dstIsAssigned = dst->getBase()->isRegVar() && dst->getBase()->asRegVar()->isPhyRegAssigned();
+                if (dstIsAssigned && dst->getLinearizedStart() % 16 != 0)
+                {
+                    assert(false && "destination of move instruction with V/VF imm is not 16-byte aligned");
+                }
+            }
         }
     }
 }

visa/LocalRA.cpp

@@ -2311,43 +2311,32 @@ bool PhyRegsLocalRA::findFreeSingleReg(int regIdx, G4_SubReg_Align subalign, int
             found = true;
         }
     }
-    else if (subalign == Eight_Word || subalign == Four_Word)
+    else
     {
-        for (int j = 0; j < (NUM_WORDS_PER_GRF - size + 1) && found == false; j += 4)
+        // ToDo: check if dynamic step size has compile time impact
+        int step = 1;
+        int upBound = NUM_WORDS_PER_GRF - size + 1;
+        switch (subalign)
         {
-            if (isWordBusy(regIdx, j, size) == false)
-            {
-                subregnum = j;
-                found = true;
-            }
+            case Eight_Word: step = 8; break;
+            case Four_Word: step = 4; break;
+            case Even_Word: step = 2; break;
+            case Any:
+                upBound = NUM_WORDS_PER_GRF - size; //FIXME, why not the last word
+                step = 1; break;
+            default:
+                assert("unexpected alignment");
         }
-    }
-    else if (subalign == Even_Word)
-    {
-        for (int j = 0; j < (NUM_WORDS_PER_GRF - size + 1) && found == false; j += 2)
+        for (int j = 0; j < upBound; j += step)
         {
-            if (isWordBusy(regIdx, j, size) == false)
-            {
-                subregnum = j;
-                found = true;
-            }
-        }
-    }
-    else if (subalign == Any)
-    {
-        for (int j = 0; j < (NUM_WORDS_PER_GRF - size) && found == false; j++)
-        {
-            if (isWordBusy(regIdx, j, size) == false)
+            if (!isWordBusy(regIdx, j, size))
             {
                 subregnum = j;
                 found = true;
+                break;
             }
         }
     }
-    else
-    {
-        ASSERT_USER(false, "Dont know how to allocate this sub-alignment");
-    }
 
     if (found)
     {