8063137: Never-taken branches should be pruned when GWT LambdaForms are shared

Reviewed-by: jrose, kvn

src/share/classes/java/lang/invoke/InvokerBytecodeGenerator.java

@@ -635,7 +635,6 @@ class InvokerBytecodeGenerator {
             mv.visitAnnotation("Ljava/lang/invoke/DontInline;", true);
         }
 
-
         // iterate over the form's names, generating bytecode instructions for each
         // start iterating at the first name following the arguments
         Name onStack = null;

src/share/classes/java/lang/invoke/LambdaForm.java

@@ -244,7 +244,7 @@ class LambdaForm {
 
     LambdaForm(String debugName,
                int arity, Name[] names, int result) {
-        this(debugName, arity, names, result, true);
+        this(debugName, arity, names, result, /*forceInline=*/true);
     }
     LambdaForm(String debugName,
                int arity, Name[] names, int result, boolean forceInline) {
@@ -263,7 +263,7 @@ class LambdaForm {
     }
     LambdaForm(String debugName,
                int arity, Name[] names) {
-        this(debugName, arity, names, LAST_RESULT, true);
+        this(debugName, arity, names, LAST_RESULT, /*forceInline=*/true);
     }
     LambdaForm(String debugName,
                int arity, Name[] names, boolean forceInline) {
@@ -272,7 +272,7 @@ class LambdaForm {
     LambdaForm(String debugName,
                Name[] formals, Name[] temps, Name result) {
         this(debugName,
-             formals.length, buildNames(formals, temps, result), LAST_RESULT, true);
+             formals.length, buildNames(formals, temps, result), LAST_RESULT, /*forceInline=*/true);
     }
     LambdaForm(String debugName,
                Name[] formals, Name[] temps, Name result, boolean forceInline) {
@@ -291,10 +291,6 @@ class LambdaForm {
     }
 
     private LambdaForm(String sig) {
-        this(sig, true);
-    }
-
-    private LambdaForm(String sig, boolean forceInline) {
         // Make a blank lambda form, which returns a constant zero or null.
         // It is used as a template for managing the invocation of similar forms that are non-empty.
         // Called only from getPreparedForm.
@@ -303,7 +299,7 @@ class LambdaForm {
         this.result = (signatureReturn(sig) == V_TYPE ? -1 : arity);
         this.names = buildEmptyNames(arity, sig);
         this.debugName = "LF.zero";
-        this.forceInline = forceInline;
+        this.forceInline = true;
         assert(nameRefsAreLegal());
         assert(isEmpty());
         assert(sig.equals(basicTypeSignature())) : sig + " != " + basicTypeSignature();

src/share/classes/java/lang/invoke/MethodHandleImpl.java

@@ -597,6 +597,7 @@ import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
         static final NamedFunction NF_checkSpreadArgument;
         static final NamedFunction NF_guardWithCatch;
         static final NamedFunction NF_throwException;
+        static final NamedFunction NF_profileBoolean;
 
         static final MethodHandle MH_castReference;
         static final MethodHandle MH_selectAlternative;
@@ -614,10 +615,12 @@ import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
                 NF_guardWithCatch      = new NamedFunction(MHI.getDeclaredMethod("guardWithCatch", MethodHandle.class, Class.class,
                                                                                  MethodHandle.class, Object[].class));
                 NF_throwException      = new NamedFunction(MHI.getDeclaredMethod("throwException", Throwable.class));
+                NF_profileBoolean      = new NamedFunction(MHI.getDeclaredMethod("profileBoolean", boolean.class, int[].class));
 
                 NF_checkSpreadArgument.resolve();
                 NF_guardWithCatch.resolve();
                 NF_throwException.resolve();
+                NF_profileBoolean.resolve();
 
                 MH_castReference        = IMPL_LOOKUP.findStatic(MHI, "castReference",
                                             MethodType.methodType(Object.class, Class.class, Object.class));
@@ -697,7 +700,26 @@ import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
     @LambdaForm.Hidden
     static
     MethodHandle selectAlternative(boolean testResult, MethodHandle target, MethodHandle fallback) {
-        return testResult ? target : fallback;
+        if (testResult) {
+            return target;
+        } else {
+            return fallback;
+        }
+    }
+
+    // Intrinsified by C2. Counters are used during parsing to calculate branch frequencies.
+    @LambdaForm.Hidden
+    static
+    boolean profileBoolean(boolean result, int[] counters) {
+        // Profile is int[2] where [0] and [1] correspond to false and true occurrences respectively.
+        int idx = result ? 1 : 0;
+        try {
+            counters[idx] = Math.addExact(counters[idx], 1);
+        } catch (ArithmeticException e) {
+            // Avoid continuous overflow by halving the problematic count.
+            counters[idx] = counters[idx] / 2;
+        }
+        return result;
     }
 
     static
@@ -708,13 +730,18 @@ import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
         assert(test.type().equals(type.changeReturnType(boolean.class)) && fallback.type().equals(type));
         MethodType basicType = type.basicType();
         LambdaForm form = makeGuardWithTestForm(basicType);
-        BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLL();
         BoundMethodHandle mh;
-
         try {
-            mh = (BoundMethodHandle)
-                    data.constructor().invokeBasic(type, form,
-                        (Object) test, (Object) profile(target), (Object) profile(fallback));
+            if (PROFILE_GWT) {
+                int[] counts = new int[2];
+                mh = (BoundMethodHandle)
+                        BoundMethodHandle.speciesData_LLLL().constructor().invokeBasic(type, form,
+                                (Object) test, (Object) profile(target), (Object) profile(fallback), counts);
+            } else {
+                mh = (BoundMethodHandle)
+                        BoundMethodHandle.speciesData_LLL().constructor().invokeBasic(type, form,
+                                (Object) test, (Object) profile(target), (Object) profile(fallback));
+            }
         } catch (Throwable ex) {
             throw uncaughtException(ex);
         }
@@ -856,7 +883,10 @@ import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
         final int GET_TEST     = nameCursor++;
         final int GET_TARGET   = nameCursor++;
         final int GET_FALLBACK = nameCursor++;
+        final int GET_COUNTERS = PROFILE_GWT ? nameCursor++ : -1;
         final int CALL_TEST    = nameCursor++;
+        final int PROFILE      = (GET_COUNTERS != -1) ? nameCursor++ : -1;
+        final int TEST         = nameCursor-1; // previous statement: either PROFILE or CALL_TEST
         final int SELECT_ALT   = nameCursor++;
         final int CALL_TARGET  = nameCursor++;
         assert(CALL_TARGET == SELECT_ALT+1);  // must be true to trigger IBG.emitSelectAlternative
@@ -864,12 +894,16 @@ import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
         MethodType lambdaType = basicType.invokerType();
         Name[] names = arguments(nameCursor - ARG_LIMIT, lambdaType);
 
-        BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLL();
+        BoundMethodHandle.SpeciesData data =
+                (GET_COUNTERS != -1) ? BoundMethodHandle.speciesData_LLLL()
+                                     : BoundMethodHandle.speciesData_LLL();
         names[THIS_MH] = names[THIS_MH].withConstraint(data);
         names[GET_TEST]     = new Name(data.getterFunction(0), names[THIS_MH]);
         names[GET_TARGET]   = new Name(data.getterFunction(1), names[THIS_MH]);
         names[GET_FALLBACK] = new Name(data.getterFunction(2), names[THIS_MH]);
-
+        if (GET_COUNTERS != -1) {
+            names[GET_COUNTERS] = new Name(data.getterFunction(3), names[THIS_MH]);
+        }
         Object[] invokeArgs = Arrays.copyOfRange(names, 0, ARG_LIMIT, Object[].class);
 
         // call test
@@ -877,15 +911,18 @@ import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
         invokeArgs[0] = names[GET_TEST];
         names[CALL_TEST] = new Name(testType, invokeArgs);
 
+        // profile branch
+        if (PROFILE != -1) {
+            names[PROFILE] = new Name(Lazy.NF_profileBoolean, names[CALL_TEST], names[GET_COUNTERS]);
+        }
         // call selectAlternative
-        names[SELECT_ALT] = new Name(Lazy.MH_selectAlternative, names[CALL_TEST],
-                                     names[GET_TARGET], names[GET_FALLBACK]);
+        names[SELECT_ALT] = new Name(Lazy.MH_selectAlternative, names[TEST], names[GET_TARGET], names[GET_FALLBACK]);
 
         // call target or fallback
         invokeArgs[0] = names[SELECT_ALT];
         names[CALL_TARGET] = new Name(basicType, invokeArgs);
 
-        lform = new LambdaForm("guard", lambdaType.parameterCount(), names);
+        lform = new LambdaForm("guard", lambdaType.parameterCount(), names, /*forceInline=*/true);
 
         return basicType.form().setCachedLambdaForm(MethodTypeForm.LF_GWT, lform);
     }

src/share/classes/java/lang/invoke/MethodHandleStatics.java

@@ -48,9 +48,10 @@ import sun.misc.Unsafe;
     static final int COMPILE_THRESHOLD;
     static final int DONT_INLINE_THRESHOLD;
     static final int PROFILE_LEVEL;
+    static final boolean PROFILE_GWT;
 
     static {
-        final Object[] values = new Object[7];
+        final Object[] values = new Object[8];
         AccessController.doPrivileged(new PrivilegedAction<Void>() {
                 public Void run() {
                     values[0] = Boolean.getBoolean("java.lang.invoke.MethodHandle.DEBUG_NAMES");
@@ -60,6 +61,7 @@ import sun.misc.Unsafe;
                     values[4] = Integer.getInteger("java.lang.invoke.MethodHandle.COMPILE_THRESHOLD", 0);
                     values[5] = Integer.getInteger("java.lang.invoke.MethodHandle.DONT_INLINE_THRESHOLD", 30);
                     values[6] = Integer.getInteger("java.lang.invoke.MethodHandle.PROFILE_LEVEL", 0);
+                    values[7] = Boolean.parseBoolean(System.getProperty("java.lang.invoke.MethodHandle.PROFILE_GWT", "true"));
                     return null;
                 }
             });
@@ -70,6 +72,7 @@ import sun.misc.Unsafe;
         COMPILE_THRESHOLD         = (Integer) values[4];
         DONT_INLINE_THRESHOLD     = (Integer) values[5];
         PROFILE_LEVEL             = (Integer) values[6];
+        PROFILE_GWT               = (Boolean) values[7];
     }
 
     /** Tell if any of the debugging switches are turned on.