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*
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* version 2 for more details (a copy is included in the LICENSE file that
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*
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* 2 along with this work; if not, write to the Free Software Foundation,
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package org.graalvm.compiler.phases.graph;
import org.graalvm.compiler.core.common.type.ObjectStamp;
import org.graalvm.compiler.graph.Node;
import org.graalvm.compiler.nodes.StructuredGraph;
import org.graalvm.compiler.nodes.ValueNode;
import org.graalvm.compiler.nodes.ValuePhiNode;
public class InferStamps {
/**
* Infer the stamps for all Object nodes in the graph, to make the stamps as precise as
* possible. For example, this propagates the word-type through phi functions. To handle phi
* functions at loop headers, the stamp inference is called until a fix point is reached.
* <p>
* This method can be used when it is needed that stamps are inferred before the first run of
* the canonicalizer. For example, word type rewriting must run before the first run of the
* canonicalizer because many nodes are not prepared to see the word type during
* canonicalization.
*/
public static void inferStamps(StructuredGraph graph) {
/*
* We want to make the stamps more precise. For cyclic phi functions, this means we have to
* ignore the initial stamp because the imprecise stamp would always propagate around the
* cycle. We therefore set the stamp to an illegal stamp, which is automatically ignored
* when the phi function performs the "meet" operator on its input stamps.
*/
for (Node n : graph.getNodes()) {
if (n instanceof ValuePhiNode) {
ValueNode node = (ValueNode) n;
if (node.stamp() instanceof ObjectStamp) {
assert node.stamp().hasValues() : "We assume all Phi and Proxy stamps are legal before the analysis";
node.setStamp(node.stamp().empty());
}
}
}
boolean stampChanged;
// The algorithm is not guaranteed to reach a stable state.
int z = 0;
do {
stampChanged = false;
/*
* We could use GraphOrder.forwardGraph() to process the nodes in a defined order and
* propagate long def-use chains in fewer iterations. However, measurements showed that
* we have few iterations anyway, and the overhead of computing the order is much higher
* than the benefit.
*/
for (Node n : graph.getNodes()) {
if (n instanceof ValueNode) {
ValueNode node = (ValueNode) n;
if (node.stamp() instanceof ObjectStamp) {
stampChanged |= node.inferStamp();
}
}
}
++z;
} while (stampChanged && z < 10000);
/*
* Check that all the illegal stamps we introduced above are correctly replaced with real
* stamps again.
*/
assert checkNoEmptyStamp(graph);
}
private static boolean checkNoEmptyStamp(StructuredGraph graph) {
for (Node n : graph.getNodes()) {
if (n instanceof ValuePhiNode) {
ValueNode node = (ValueNode) n;
assert node.stamp().hasValues() : "Stamp is empty after analysis. This is not necessarily an error, but a condition that we want to investigate (and then maybe relax or remove the assertion).";
}
}
return true;
}
}