[CGP] Fix the detection of trivial case for addressing mode

[skatkov]

Summary

The address can be presented as a bitcast of baseReg.
In this case it is still trivial but OriginalValue != baseReg.

[skatkov]

ping

[hfinkel]

This logic certainly looks cleaner.

lib/CodeGen/CodeGenPrepare.cpp

2730

is alone field -> is the only populated field

[skatkov]

Landed at rL316980

lib/CodeGen/CodeGenPrepare.cpp

if (Scale && other.Scale && Scale != other.Scale)
       Result |= ScaleField;
 
     if (countPopulation(Result) > 1)
       return MultipleFields;
     else
       return static_cast<FieldName>(Result);
   }
 
-  // AddrModes with a base reg or gv where the reg/gv is just the original
-  // value are trivial.
+  // AddrModes with a baseReg or gv where the reg/gv is alone field are trivial.
   bool isTrivial() {
-    bool Trivial = (BaseGV && BaseGV == OriginalValue) ||
-      (BaseReg && BaseReg == OriginalValue);
-    // If the AddrMode is trivial it shouldn't have an offset or be scaled.
-    if (Trivial) {
-      assert(BaseOffs == 0);
-      assert(Scale == 0);
-    }
-    return Trivial;
+    if (BaseGV && !BaseOffs && !Scale && !BaseReg)
+      return true;
+
+    if (!BaseGV && !BaseOffs && !Scale && BaseReg)
+      return true;
+
+    return false;
   }
 };
 
 } // end anonymous namespace
 
 #ifndef NDEBUG
 static inline raw_ostream &operator<<(raw_ostream &OS, const ExtAddrMode &AM) {
   AM.print(OS);