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package com.oracle.truffle.api;
import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
import com.oracle.truffle.api.nodes.ExplodeLoop;
import com.oracle.truffle.api.nodes.InvalidAssumptionException;
import com.oracle.truffle.api.nodes.Node;
/**
* An assumption is a global boolean flag that starts with the value true (i.e., the assumption is
* valid) and can subsequently be invalidated (using {@link Assumption#invalidate()}). Once
* invalidated, an assumption can never get valid again. Assumptions can be created using the
* {@link TruffleRuntime#createAssumption()} or the {@link TruffleRuntime#createAssumption(String)}
* method. The Truffle compiler has special knowledge of this class in order to produce efficient
* machine code for checking an assumption in case the assumption object is a compile time constant.
* Therefore, assumptions should be stored in final fields in Truffle nodes.
*
* All instances of classes implementing {@code Assumption} must be held in {@code final} fields for
* compiler optimizations to take effect.
*
* Do not manually subclass the {@link Assumption} interface. This class is only intended to be
* subclassed by Truffle runtime implementations to avoid polymorphism in performance sensitive
* methods.
*
* @since 0.8 or earlier
*/
public interface Assumption {
/**
* An assumption that is always valid and fails with an {@link UnsupportedOperationException} if
* invalidated.
*
* @since 22.1
*/
Assumption ALWAYS_VALID = createAlwaysValid();
/**
* An assumption that is never valid.
*
* @since 22.1
*/
Assumption NEVER_VALID = createNeverValid();
private static Assumption createNeverValid() {
Assumption assumption = create("");
assumption.invalidate();
return assumption;
}
private static Assumption createAlwaysValid() {
return LanguageAccessor.RUNTIME.createAlwaysValidAssumption();
}
/**
* Checks that this assumption is still valid. The method throws an exception, if this is no
* longer the case. This method is preferred over the {@link #isValid()} method when writing
* guest language interpreter code. The catch block should perform a node rewrite (see
* {@link Node#replace(Node)}) with a node that no longer relies on the assumption.
*
* @throws InvalidAssumptionException If the assumption is no longer valid.
* @since 0.8 or earlier
*/
void check() throws InvalidAssumptionException;
/**
* Checks whether the assumption is still valid.
*
* @return a boolean value indicating the validity of the assumption
* @since 0.8 or earlier
*/
boolean isValid();
/**
* Invalidates this assumption. Performs no operation, if the assumption is already invalid.
*
* @since 0.8 or earlier
*/
void invalidate();
/**
* Invalidates this assumption. Performs no operation, if the assumption is already invalid.
*
* @param message a message stating the reason of the invalidation
* @since 0.33
*/
default void invalidate(String message) {
invalidate();
}
/**
* A name for the assumption that is used for debug output.
*
* @return the name of the assumption
* @since 0.8 or earlier
*/
String getName();
/**
* Checks whether an assumption is not null and valid.
*
* @since 19.0
*/
static boolean isValidAssumption(Assumption assumption) {
return assumption != null && assumption.isValid();
}
/**
* Checks whether all assumptions in an array are not null and valid. Returns
* false if the assumptions array itself is null. This method is
* designed for compilation. Note that the provided assumptions array must be a compilation
* final array with {@link CompilationFinal#dimensions() dimensions} set to one.
*
* @since 19.0
*/
@ExplodeLoop
static boolean isValidAssumption(Assumption[] assumptions) {
CompilerAsserts.partialEvaluationConstant(assumptions);
if (assumptions == null) {
return false;
}
for (Assumption assumption : assumptions) {
if (!isValidAssumption(assumption)) {
return false;
}
}
return true;
}
/**
* Creates a new assumption with a name. Shortcut for {@link TruffleRuntime#createAssumption()}.
*
* @since 22.1
*/
static Assumption create() {
return Truffle.getRuntime().createAssumption();
}
/**
* Creates a new assumption with a name. Shortcut for
* {@link TruffleRuntime#createAssumption(String)}.
*
* @since 22.1
*/
static Assumption create(String name) {
return Truffle.getRuntime().createAssumption(name);
}
}