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8153637: MethodHandles.countedLoop/3 initialises loop counter to 1 instead of 0

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Reviewed-by: psandoz, redestad
This commit is contained in:
Michael Haupt 2016-04-13 09:20:22 +02:00
parent fd0239a0bc
commit c304110149
3 changed files with 46 additions and 4 deletions
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18
jdk/src/java.base/share/classes/java/lang/invoke/MethodHandleImpl.java
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@ -1753,6 +1753,18 @@ import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
return counter + 1;
}
/**
* This method is bound as a filter in {@linkplain MethodHandles#countedLoop(MethodHandle, MethodHandle, MethodHandle,
* MethodHandle) counting loops} to pass the correct counter value to the body.
*
* @param counter the loop counter.
*
* @return the loop counter decremented by 1.
*/
static int decrementCounter(int counter) {
return counter - 1;
}
/**
* This is bound to initialize the loop-local iterator in {@linkplain MethodHandles#iteratedLoop iterating loops}.
*
@ -1879,7 +1891,8 @@ import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
MH_iterateNext = 11,
MH_tryFinallyExec = 12,
MH_tryFinallyVoidExec = 13,
MH_LIMIT = 14;
MH_decrementCounter = 14,
MH_LIMIT = 15;
static MethodHandle getConstantHandle(int idx) {
MethodHandle handle = HANDLES[idx];
@ -1949,6 +1962,9 @@ import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
case MH_tryFinallyVoidExec:
return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "tryFinallyVoidExecutor",
MethodType.methodType(void.class, MethodHandle.class, MethodHandle.class, Object[].class));
case MH_decrementCounter:
return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "decrementCounter",
MethodType.methodType(int.class, int.class));
}
} catch (ReflectiveOperationException ex) {
throw newInternalError(ex);

10
jdk/src/java.base/share/classes/java/lang/invoke/MethodHandles.java
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@ -4322,11 +4322,13 @@ assertEquals("boojum", (String) catTrace.invokeExact("boo", "jum"));
* <blockquote><pre>{@code
* MethodHandle countedLoop(MethodHandle start, MethodHandle end, MethodHandle init, MethodHandle body) {
* MethodHandle returnVar = dropArguments(identity(init.type().returnType()), 0, int.class, int.class);
* // assume MH_increment and MH_lessThan are handles to x+1 and x<y of type int
* // assume MH_increment and MH_lessThan are handles to x+1 and x<y of type int,
* // assume MH_decrement is a handle to x-1 of type int
* MethodHandle[]
* indexVar = {start, MH_increment}, // i = start; i = i+1
* loopLimit = {end, null, MH_lessThan, returnVar }, // i<end
* bodyClause = {init, dropArguments(body, 1, int.class)}; // v = body(i, v);
* bodyClause = {init,
* filterArgument(dropArguments(body, 1, int.class), 0, MH_decrement}; // v = body(i-1, v)
* return loop(indexVar, loopLimit, bodyClause);
* }
* }</pre></blockquote>
@ -4351,7 +4353,9 @@ assertEquals("boojum", (String) catTrace.invokeExact("boo", "jum"));
0, int.class, int.class);
MethodHandle[] indexVar = {start, MethodHandleImpl.getConstantHandle(MethodHandleImpl.MH_countedLoopStep)};
MethodHandle[] loopLimit = {end, null, MethodHandleImpl.getConstantHandle(MethodHandleImpl.MH_countedLoopPred), returnVar};
MethodHandle[] bodyClause = {init, dropArguments(body, 1, int.class)};
MethodHandle[] bodyClause = {init,
filterArgument(dropArguments(body, 1, int.class), 0,
MethodHandleImpl.getConstantHandle(MethodHandleImpl.MH_decrementCounter))};
return loop(indexVar, loopLimit, bodyClause);
}

22
jdk/test/java/lang/invoke/LoopCombinatorTest.java
View File

@ -26,6 +26,8 @@
/* @test
* @bug 8139885
* @bug 8150635
* @bug 8150957
* @bug 8153637
* @run testng/othervm -ea -esa test.java.lang.invoke.LoopCombinatorTest
*/
@ -301,6 +303,18 @@ public class LoopCombinatorTest {
assertEquals("na na na na na na na na na na na na na Lambdaman!", loop.invoke("Lambdaman!"));
}
@Test
public static void testCountedLoopCounterInit() throws Throwable {
// int x = 0; for (int i = 0; i < 5; ++i) { x += i; } return x; => 10
// (only if counter's first value in body is 0)
MethodHandle iter = MethodHandles.constant(int.class, 5);
MethodHandle init = MethodHandles.constant(int.class, 0);
MethodHandle body = Counted.MH_addCounter;
MethodHandle loop = MethodHandles.countedLoop(iter, init, body);
assertEquals(Counted.MT_counterInit, loop.type());
assertEquals(10, loop.invoke());
}
@Test
public static void testIterateSum() throws Throwable {
// Integer[] a = new Integer[]{1,2,3,4,5,6}; int sum = 0; for (int e : a) { sum += e; } return sum; => 21
@ -667,12 +681,17 @@ public class LoopCombinatorTest {
System.out.print("hello");
}
static int addCounter(int counter, int x) {
return x + counter;
}
static final Class<Counted> COUNTED = Counted.class;
static final MethodType MT_start = methodType(String.class, String.class);
static final MethodType MT_step = methodType(String.class, int.class, String.class, String.class);
static final MethodType MT_stepUpdateArray = methodType(void.class, int.class, int[].class);
static final MethodType MT_printHello = methodType(void.class, int.class);
static final MethodType MT_addCounter = methodType(int.class, int.class, int.class);
static final MethodHandle MH_13;
static final MethodHandle MH_m5;
@ -681,10 +700,12 @@ public class LoopCombinatorTest {
static final MethodHandle MH_step;
static final MethodHandle MH_stepUpdateArray;
static final MethodHandle MH_printHello;
static final MethodHandle MH_addCounter;
static final MethodType MT_counted = methodType(String.class, String.class);
static final MethodType MT_arrayCounted = methodType(void.class, int[].class);
static final MethodType MT_countedPrinting = methodType(void.class);
static final MethodType MT_counterInit = methodType(int.class);
static {
try {
@ -695,6 +716,7 @@ public class LoopCombinatorTest {
MH_step = LOOKUP.findStatic(COUNTED, "step", MT_step);
MH_stepUpdateArray = LOOKUP.findStatic(COUNTED, "stepUpdateArray", MT_stepUpdateArray);
MH_printHello = LOOKUP.findStatic(COUNTED, "printHello", MT_printHello);
MH_addCounter = LOOKUP.findStatic(COUNTED, "addCounter", MT_addCounter);
} catch (Exception e) {
throw new ExceptionInInitializerError(e);
}