[IPO] Avoid repeated hash lookups (NFC) (llvm#125639)

The two "if" conditions are mutually exclusive, so we can put them in
any order.  Reversing the order allows us to remove
Blocks.contains(IncomingBlock) in one of the "if" conditions.

Author: kazutakahirata

llvm/lib/Transforms/IPO/IROutliner.cpp

@@ -1184,22 +1184,22 @@ static std::optional<unsigned> getGVNForPHINode(OutlinableRegion &Region,
   for (unsigned Idx = 0, EIdx = PN->getNumIncomingValues(); Idx < EIdx; Idx++) {
     Incoming = PN->getIncomingValue(Idx);
     IncomingBlock = PN->getIncomingBlock(Idx);
+    // If the incoming block isn't in the region, we don't have to worry about
+    // this incoming value.
+    if (!Blocks.contains(IncomingBlock))
+      continue;
+
     // If we cannot find a GVN, and the incoming block is included in the region
     // this means that the input to the PHINode is not included in the region we
     // are trying to analyze, meaning, that if it was outlined, we would be
     // adding an extra input.  We ignore this case for now, and so ignore the
     // region.
     std::optional<unsigned> OGVN = Cand.getGVN(Incoming);
-    if (!OGVN && Blocks.contains(IncomingBlock)) {
+    if (!OGVN) {
       Region.IgnoreRegion = true;
       return std::nullopt;
     }
 
-    // If the incoming block isn't in the region, we don't have to worry about
-    // this incoming value.
-    if (!Blocks.contains(IncomingBlock))
-      continue;
-
     // Collect the canonical numbers of the values in the PHINode.
     unsigned GVN = *OGVN;
     OGVN = Cand.getCanonicalNum(GVN);