[CodeGen] Make logic of resultsCompatible clearer

[efriedma]

Maybe it would be more straightforward to use CCValAssign::getExtraInfo()? Either way is fine, I guess.

llvm/lib/CodeGen/CallingConvLower.cpp

288

Don't need braces on innermost if.

[DavidSpickett]

• Use getExtraInfo after checking we have two registers or two memory offsets.

[efriedma]

LGTM with one minor comment.

llvm/lib/CodeGen/CallingConvLower.cpp

281

Don't need parentheses around each compare.

[DavidSpickett]

Committed as d782d1f898eaafee49548d5332e84c3ae11ebac4. (closing manually because I forgot to add the revision line to the commit msg)

[DavidSpickett]

Reverted due to CodeGen/X86/sibcall.ll failing, will investigate.

[DavidSpickett]

Relanded as 055ea585c77cd8ae9cd3bc327c1e4404020fdf27 with a typo fixed. This:
(Loc1.getExtraInfo() != Loc1.getExtraInfo()
Is now:
(Loc1.getExtraInfo() != Loc2.getExtraInfo())

llvm/lib/CodeGen/CallingConvLower.cpp

bool CCState::resultsCompatible(CallingConv::ID CalleeCC,
   CCState CCInfo2(CallerCC, false, MF, RVLocs2, C);
   CCInfo2.AnalyzeCallResult(Ins, CallerFn);
 
   if (RVLocs1.size() != RVLocs2.size())
     return false;
   for (unsigned I = 0, E = RVLocs1.size(); I != E; ++I) {
     const CCValAssign &Loc1 = RVLocs1[I];
     const CCValAssign &Loc2 = RVLocs2[I];
-    if (Loc1.getLocInfo() != Loc2.getLocInfo())
-      return false;
-    bool RegLoc1 = Loc1.isRegLoc();
-    if (RegLoc1 != Loc2.isRegLoc())
-      return false;
-    if (RegLoc1) {
-      if (Loc1.getLocReg() != Loc2.getLocReg())
-        return false;
-    } else {
-      if (Loc1.getLocMemOffset() != Loc2.getLocMemOffset())
-        return false;
-    }
-  }
+
+    if ( // Must both be in registers, or both in memory
+        (Loc1.isRegLoc() != Loc2.isRegLoc()) ||
+        // Must fill the same part of their locations
+        (Loc1.getLocInfo() != Loc2.getLocInfo()) ||
+        // Memory offset/register number must be the same
+        (Loc1.getExtraInfo() != Loc1.getExtraInfo()))
   return true;
 }