Less add3

Only benefit of add3 is less instructions. For now,
simply skip if there are more than one use of the second
add as it is not guaranteed to be removed.

This is to try if this scheme works. If not, a better
approach has to be developed.

Author: jgu222

IGC/Compiler/CISACodeGen/PatternMatchPass.cpp

@@ -4191,6 +4191,10 @@ namespace IGC
             return false;
         }
 
+        // For simplicity, do not do add3 if 'Add2' has more than one use.
+        if (!Add2->hasOneUse())
+            return false;
+
         // If source operand corresponding to first add instruction
         // has many uses the add3 pattern match is unlikely to be profitable,
         // as it increases register pressure and makes register bank