relax ACC substitution constraints

Change-Id: I9093708284f580492ac4449429fcbf73f16c8ecb

Author: bcheng0127

visa/Gen4_IR.cpp

@@ -7822,11 +7822,6 @@ bool G4_INST::canSrcBeAcc(Gen4_Operand_Number opndNum) const
     }
 
     G4_SrcRegRegion* src = getSrc(srcId)->asSrcRegRegion();
-    if (srcId == 1 && src->getModifier() != Mod_src_undef)
-    {
-        // src1 acc does not support modifiers
-        return false;
-    }
     if (!src->getRegion()->isContiguous(getExecSize()))
     {
         return false;
@@ -7917,7 +7912,7 @@ bool G4_INST::canSrcBeAcc(Gen4_Operand_Number opndNum) const
     case G4_mad:
         // no int acc if it's used as mul operand
         return builder.canMadHaveAcc() &&
-            ((srcId == 1 && (IS_FTYPE(src->getType()) || (src->getType() == Type_DF))) || (srcId == 0 && src->getModifier() == Mod_src_undef));
+            (IS_FTYPE(src->getType()) || (src->getType() == Type_DF));
     case G4_csel:
         return builder.canMadHaveAcc();
     case G4_mul:

visa/HWConformity.cpp

@@ -4392,7 +4392,10 @@ static bool isAccCandidate(G4_INST* inst, G4_Kernel& kernel, int& lastUse, bool&
         }
         else if (opndNum != Opnd_src0)
         {
-            return false;
+            if (!useInst->canSwapSource())
+            {
+                return false;
+            }
         }
 
         if (useInst->getSingleDef(opndNum) == nullptr)
@@ -4503,6 +4506,22 @@ static bool replaceDstWithAcc(G4_INST* inst, int accNum, IR_Builder& builder)
                 return false;
             }
         }
+
+        if (useInst->getNumSrc() == 2)
+        {
+            if (use.second != Opnd_src0)
+            {
+                if (useInst->canSwapSource() && !useInst->getSrc(0)->isAccReg())
+                {
+                    useInst->swapSrc(0, 1);
+                    use.second = Opnd_src0;
+                }
+                else
+                {
+                    return false;
+                }
+            }
+        }
     }
 
     // at this point acc substitution must succeed