RequirementMachine: Use llvm::array_pod_sort() to sort requirements

Author: slavapestov

lib/AST/GenericSignature.cpp

@@ -1483,7 +1483,11 @@ int Requirement::compare(const Requirement &other) const {
   // We should only have multiple conformance requirements.
   assert(getKind() == RequirementKind::Conformance);
 
-  return TypeDecl::compare(getProtocolDecl(), other.getProtocolDecl());
+  int compareProtos =
+    TypeDecl::compare(getProtocolDecl(), other.getProtocolDecl());
+  assert(compareProtos != 0 && "Duplicate conformance requirements");
+
+  return compareProtos;
 }
 
 /// Compare two associated types.

lib/AST/RequirementMachine/RequirementMachineRequests.cpp

@@ -193,10 +193,10 @@ RequirementMachine::buildRequirementSignature(ArrayRef<unsigned> rules,
   }
 
   // Finally, sort the requirements in canonical order.
-  std::sort(reqs.begin(), reqs.end(),
-            [](const Requirement &lhs, const Requirement &rhs) -> bool {
-              return lhs.compare(rhs) < 0;
-            });
+  llvm::array_pod_sort(reqs.begin(), reqs.end(),
+                       [](const Requirement *lhs, const Requirement *rhs) -> int {
+                         return lhs->compare(*rhs);
+                       });
 
   return reqs;
 }