Use separate random number generator for each randomization pass

src/IceTargetLoweringX8632Traits.h

Index: src/IceTargetLoweringX8632Traits.h
diff --git a/src/IceTargetLoweringX8632Traits.h b/src/IceTargetLoweringX8632Traits.h
index e0acbd674ce6f55011a30bad3566230235588ee2..def7843234f569dfa122a56a54d152af2bdd05ff 100644
--- a/src/IceTargetLoweringX8632Traits.h
+++ b/src/IceTargetLoweringX8632Traits.h
@@ -393,13 +393,18 @@ template <> struct MachineTraits<TargetX8632> {
     REGX8632_TABLE
 #undef X
 
-    RandomNumberGeneratorWrapper RNG(Ctx->getRNG());
+    // Create a random number generator for regalloc randomization.
+    // Use function's sequence as the salt.
+    RandomNumberGenerator RNG(Ctx->getFlags().getRandomSeed(),
+                              RS_RegAllocRandomization,
+                              Func->getSequenceNumber());
+    RandomNumberGeneratorWrapper RNGW(RNG);
 
     // Shuffle the resulting equivalence classes.
     for (auto I : EquivalenceClasses) {
       const RegisterList &List = I.second;
       RegisterList Shuffled(List);
-      RandomShuffle(Shuffled.begin(), Shuffled.end(), RNG);
+      RandomShuffle(Shuffled.begin(), Shuffled.end(), RNGW);
       for (size_t SI = 0, SE = Shuffled.size(); SI < SE; ++SI) {
         Permutation[List[SI]] = Shuffled[SI];
         ++NumShuffled;