Bug 1170840 - Add testbed allocator for new regalloc features, and use for a change to hot/cold code bundle splitting, r=sunfish.

js/src/jit/BacktrackingAllocator.cpp

@@ -2511,6 +2511,13 @@ BacktrackingAllocator::trySplitAcrossHotcode(LiveBundle* bundle, bool* success)
         return false;
     LiveBundle* preBundle = nullptr;
     LiveBundle* postBundle = nullptr;
+    LiveBundle* coldBundle = nullptr;
+
+    if (testbed) {
+        coldBundle = LiveBundle::New(alloc(), bundle->spillSet(), bundle->spillParent());
+        if (!coldBundle)
+            return false;
+    }
 
     // Accumulate the ranges of hot and cold code in the bundle. Note that
     // we are only comparing with the single hot range found, so the cold code
@@ -2526,6 +2533,10 @@ BacktrackingAllocator::trySplitAcrossHotcode(LiveBundle* bundle, bool* success)
         }
 
         if (!coldPre.empty()) {
+            if (testbed) {
+                if (!coldBundle->addRangeAndDistributeUses(alloc(), range, coldPre.from, coldPre.to))
+                    return false;
+            } else {
                 if (!preBundle) {
                     preBundle = LiveBundle::New(alloc(), bundle->spillSet(), bundle->spillParent());
                     if (!preBundle)
@@ -2534,25 +2545,41 @@ BacktrackingAllocator::trySplitAcrossHotcode(LiveBundle* bundle, bool* success)
                 if (!preBundle->addRangeAndDistributeUses(alloc(), range, coldPre.from, coldPre.to))
                     return false;
             }
+        }
 
         if (!coldPost.empty()) {
-            if (!postBundle)
+            if (testbed) {
+                if (!coldBundle->addRangeAndDistributeUses(alloc(), range, coldPost.from, coldPost.to))
+                    return false;
+            } else {
+                if (!postBundle) {
                     postBundle = LiveBundle::New(alloc(), bundle->spillSet(), bundle->spillParent());
+                    if (!postBundle)
+                        return false;
+                }
                 if (!postBundle->addRangeAndDistributeUses(alloc(), range, coldPost.from, coldPost.to))
                     return false;
             }
         }
+    }
 
-    MOZ_ASSERT(preBundle || postBundle);
     MOZ_ASSERT(hotBundle->numRanges() != 0);
 
     LiveBundleVector newBundles;
     if (!newBundles.append(hotBundle))
         return false;
+
+    if (testbed) {
+        MOZ_ASSERT(coldBundle->numRanges() != 0);
+        if (!newBundles.append(coldBundle))
+            return false;
+    } else {
+        MOZ_ASSERT(preBundle || postBundle);
         if (preBundle && !newBundles.append(preBundle))
             return false;
         if (postBundle && !newBundles.append(postBundle))
             return false;
+    }
 
     *success = true;
     return splitAndRequeueBundles(bundle, newBundles);

js/src/jit/BacktrackingAllocator.h

@@ -546,6 +546,9 @@ class BacktrackingAllocator : protected RegisterAllocator
     friend class C1Spewer;
     friend class JSONSpewer;
 
+    // This flag is set when testing new allocator modifications.
+    bool testbed;
+
     BitSet* liveIn;
     FixedList<VirtualRegister> vregs;
 
@@ -606,8 +609,9 @@ class BacktrackingAllocator : protected RegisterAllocator
     SpillSlotList normalSlots, doubleSlots, quadSlots;
 
   public:
-    BacktrackingAllocator(MIRGenerator* mir, LIRGenerator* lir, LIRGraph& graph)
+    BacktrackingAllocator(MIRGenerator* mir, LIRGenerator* lir, LIRGraph& graph, bool testbed)
       : RegisterAllocator(mir, lir, graph),
+        testbed(testbed),
         liveIn(nullptr),
         callRanges(nullptr)
     { }

js/src/jit/Ion.cpp

@@ -1653,14 +1653,18 @@ GenerateLIR(MIRGenerator* mir)
     {
         AutoTraceLog log(logger, TraceLogger_RegisterAllocation);
 
-        switch (mir->optimizationInfo().registerAllocator()) {
-          case RegisterAllocator_Backtracking: {
+        IonRegisterAllocator allocator = mir->optimizationInfo().registerAllocator();
+
+        switch (allocator) {
+          case RegisterAllocator_Backtracking:
+          case RegisterAllocator_Testbed: {
 #ifdef DEBUG
             if (!integrity.record())
                 return nullptr;
 #endif
 
-            BacktrackingAllocator regalloc(mir, &lirgen, *lir);
+            BacktrackingAllocator regalloc(mir, &lirgen, *lir,
+                                           allocator == RegisterAllocator_Testbed);
             if (!regalloc.go())
                 return nullptr;
 

js/src/jit/JitOptions.h

@@ -23,6 +23,7 @@ static const uint32_t MAX_MAIN_THREAD_LOCALS_AND_ARGS = 256;
 // Possible register allocators which may be used.
 enum IonRegisterAllocator {
     RegisterAllocator_Backtracking,
+    RegisterAllocator_Testbed,
     RegisterAllocator_Stupid
 };
 
@@ -31,6 +32,8 @@ LookupRegisterAllocator(const char* name)
 {
     if (!strcmp(name, "backtracking"))
         return mozilla::Some(RegisterAllocator_Backtracking);
+    if (!strcmp(name, "testbed"))
+        return mozilla::Some(RegisterAllocator_Testbed);
     if (!strcmp(name, "stupid"))
         return mozilla::Some(RegisterAllocator_Stupid);
     return mozilla::Nothing();

js/src/shell/js.cpp

@@ -6292,6 +6292,7 @@ main(int argc, char** argv, char** envp)
         || !op.addStringOption('\0', "ion-regalloc", "[mode]",
                                "Specify Ion register allocation:\n"
                                "  backtracking: Priority based backtracking register allocation (default)\n"
+                               "  testbed: Backtracking allocator with experimental features\n"
                                "  stupid: Simple block local register allocation")
         || !op.addBoolOption('\0', "ion-eager", "Always ion-compile methods (implies --baseline-eager)")
         || !op.addStringOption('\0', "ion-offthread-compile", "on/off",