Subzero: Use a "deterministic" random shuffle for register allocation.

unittest/IceELFSectionTest.cpp

 //===- unittest/IceELFSectionTest.cpp - ELF Section unit tests ------------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include <algorithm>
@@ skipping 72 matching lines @@
   Strings.push_back("a");
   Strings.push_back("z");
   Strings.push_back("foo");
   Strings.push_back("bar");
   Strings.push_back(".text");
   Strings.push_back(".symtab");
   Strings.push_back(".strtab");
   Strings.push_back(".shstrtab");
   Strings.push_back("_start");
   const SizeT NumTests = 128;
+  const uint64_t RandomSeed = 12345; // arbitrary value for now
+  RandomNumberGenerator R(RandomSeed);
+  RandomNumberGeneratorWrapper RNG(R);
   for (SizeT i = 0; i < NumTests; ++i) {
-    std::random_shuffle(Strings.begin(), Strings.end());
+    RandomShuffle(Strings.begin(), Strings.end(), RNG);
     ELFStringTableSection Strtab(".strtab", SHT_STRTAB, 0, 1, 0);
     for (auto &S : Strings) {
       Strtab.add(S);
     }
     Strtab.doLayout();
     CheckStringTablePermLayout(Strtab);
   }
 }
 
 // Test that adding duplicate strings is fine.
@@ skipping 20 matching lines @@
   Strtab.add("lollipop");
   Strtab.add("pop");
   Strtab.add("unpop");
 
   Strtab.doLayout();
   CheckStringTablePermLayout(Strtab);
 }
 
 } // end of anonymous namespace
 } // end of namespace Ice