Bug 773655 - Don't destroy JM code before Ion compilation. r=bhackett

js/src/methodjit/Compiler.cpp

@@ -1008,6 +1008,19 @@ mjit::CanMethodJIT(JSContext *cx, JSScript *script, jsbytecode *pc,
     unsigned chunkIndex = jit->chunkIndex(pc);
     ChunkDescriptor &desc = jit->chunkDescriptor(chunkIndex);
 
+    if (jit->mustDestroyEntryChunk) {
+        // We kept this chunk around so that Ion can get info from its caches.
+        // If we end up here, we decided not to use Ion so we can destroy the
+        // chunk now.
+        JS_ASSERT(jit->nchunks == 1);
+        jit->mustDestroyEntryChunk = false;
+
+        if (desc.chunk) {
+            jit->destroyChunk(cx->runtime->defaultFreeOp(), chunkIndex, /* resetUses = */ false);
+            return Compile_Skipped;
+        }
+    }
+
     if (desc.chunk)
         return Compile_Okay;
 

js/src/methodjit/MethodJIT.cpp

@@ -1306,23 +1306,7 @@ JITScript::destroyChunk(FreeOp *fop, unsigned chunkIndex, bool resetUses)
             argsCheckPool = NULL;
         }
 
-        invokeEntry = NULL;
-        fastEntry = NULL;
-        argsCheckEntry = NULL;
-        arityCheckEntry = NULL;
-
-        // Fixup any ICs still referring to this chunk.
-        while (!JS_CLIST_IS_EMPTY(&callers)) {
-            JS_STATIC_ASSERT(offsetof(ic::CallICInfo, links) == 0);
-            ic::CallICInfo *ic = (ic::CallICInfo *) callers.next;
-
-            uint8_t *start = (uint8_t *)ic->funGuard.executableAddress();
-            JSC::RepatchBuffer repatch(JSC::JITCode(start - 32, 64));
-
-            repatch.repatch(ic->funGuard, NULL);
-            repatch.relink(ic->funJump, ic->slowPathStart);
-            ic->purgeGuardedObject();
-        }
+        disableScriptEntry();
     }
 }
 
@@ -1346,6 +1330,28 @@ JITScript::purgeCaches()
     }
 }
 
+void
+JITScript::disableScriptEntry()
+{
+    invokeEntry = NULL;
+    fastEntry = NULL;
+    argsCheckEntry = NULL;
+    arityCheckEntry = NULL;
+
+    // Fixup any ICs still referring to this script.
+    while (!JS_CLIST_IS_EMPTY(&callers)) {
+        JS_STATIC_ASSERT(offsetof(ic::CallICInfo, links) == 0);
+        ic::CallICInfo *ic = (ic::CallICInfo *) callers.next;
+
+        uint8_t *start = (uint8_t *)ic->funGuard.executableAddress();
+        JSC::RepatchBuffer repatch(JSC::JITCode(start - 32, 64));
+
+        repatch.repatch(ic->funGuard, NULL);
+        repatch.relink(ic->funJump, ic->slowPathStart);
+        ic->purgeGuardedObject();
+    }
+}
+
 const js::mjit::JITScript *JSScript::JITScriptHandle::UNJITTABLE =
     reinterpret_cast<js::mjit::JITScript *>(1);
 

js/src/methodjit/MethodJIT.h

@@ -779,6 +779,13 @@ struct JITScript
      */
     JSC::ExecutablePool *shimPool;
 
+    /*
+     * If set, we decided to keep the JITChunk so that Ion can access its caches.
+     * The chunk has to be destroyed the next time the script runs in JM.
+     * Note that this flag implies nchunks == 1.
+     */
+    bool mustDestroyEntryChunk;
+
 #ifdef JS_MONOIC
     /* Inline cache at function entry for checking this/argument types. */
     JSC::CodeLocationLabel argsCheckStub;
@@ -829,6 +836,8 @@ struct JITScript
 
     void trace(JSTracer *trc);
     void purgeCaches();
+
+    void disableScriptEntry();
 };
 
 /*

js/src/methodjit/StubCalls.cpp

@@ -40,6 +40,10 @@
 #include "vm/RegExpObject-inl.h"
 #include "vm/String-inl.h"
 
+#ifdef JS_ION
+#include "ion/Ion.h"
+#endif
+
 #ifdef XP_WIN
 # include "jswin.h"
 #endif
@@ -780,8 +784,25 @@ stubs::Interrupt(VMFrame &f, jsbytecode *pc)
 void JS_FASTCALL
 stubs::RecompileForInline(VMFrame &f)
 {
+    JSScript *script = f.script();
+
     ExpandInlineFrames(f.cx->compartment);
-    Recompiler::clearStackReferences(f.cx->runtime->defaultFreeOp(), f.script());
+    Recompiler::clearStackReferences(f.cx->runtime->defaultFreeOp(), script);
+
+#ifdef JS_ION
+    if (ion::IsEnabled(f.cx) && f.jit()->nchunks == 1 &&
+        script->canIonCompile() && !script->hasIonScript())
+    {
+        // After returning to the interpreter, IonMonkey will try to compile
+        // this script. Don't destroy the JITChunk immediately so that Ion
+        // still has access to its ICs.
+        JS_ASSERT(!f.jit()->mustDestroyEntryChunk);
+        f.jit()->mustDestroyEntryChunk = true;
+        f.jit()->disableScriptEntry();
+        return;
+    }
+#endif
+
     f.jit()->destroyChunk(f.cx->runtime->defaultFreeOp(), f.chunkIndex(), /* resetUses = */ false);
 }