Update the type-information after checkcast removal
We remove trivial checkcasts when we know casting the type is safe,
thus the type information will at least be the cast type. We can
therefore narrow the values further to allow for more precise
information.
Bug: 133739171
Change-Id: I3da2a45d350985a55984eaf9182fb87d9996807f
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java b/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java
index 8194593..e7c8333 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java
@@ -1993,14 +1993,32 @@
if (!appView.enableWholeProgramOptimizations()) {
return;
}
-
+ // If we can remove a CheckCast it is due to us having at least as much information about the
+ // type as the CheckCast gives. We then need to propagate that information to the users of
+ // the CheckCast to ensure further optimizations and removals of CheckCast:
+ //
+ // : 1: NewArrayEmpty v2 <- v1(1) java.lang.String[] <-- v2 = String[]
+ // ...
+ // : 2: CheckCast v5 <- v2; java.lang.Object[] <-- v5 = Object[]
+ // ...
+ // : 3: ArrayGet v7 <- v5, v6(0) <-- v7 = Object
+ // : 4: CheckCast v8 <- v7; java.lang.String <-- v8 = String
+ // ...
+ //
+ // When looking at line 2 we can conclude that the CheckCast is trivial because v2 is String[]
+ // and remove it. However, v7 is still only known to be Object and we cannot remove the
+ // CheckCast at line 4 unless we update v7 with the most precise information by narrowing the
+ // affected values of v5. We therefore have to run the type analysis after each CheckCast
+ // removal.
+ TypeAnalysis typeAnalysis = new TypeAnalysis(appView, code.method);
+ Set<Value> affectedValues = Sets.newIdentityHashSet();
InstructionIterator it = code.instructionIterator();
boolean needToRemoveTrivialPhis = false;
while (it.hasNext()) {
Instruction current = it.next();
if (current.isCheckCast()) {
boolean hasPhiUsers = current.outValue().numberOfPhiUsers() != 0;
- if (removeCheckCastInstructionIfTrivial(current.asCheckCast(), it, code)) {
+ if (removeCheckCastInstructionIfTrivial(current.asCheckCast(), it, code, affectedValues)) {
needToRemoveTrivialPhis |= hasPhiUsers;
}
} else if (current.isInstanceOf()) {
@@ -2009,6 +2027,10 @@
needToRemoveTrivialPhis |= hasPhiUsers;
}
}
+ if (!affectedValues.isEmpty()) {
+ typeAnalysis.narrowing(affectedValues);
+ affectedValues.clear();
+ }
}
// ... v1
// ...
@@ -2024,7 +2046,7 @@
// Returns true if the given check-cast instruction was removed.
private boolean removeCheckCastInstructionIfTrivial(
- CheckCast checkCast, InstructionIterator it, IRCode code) {
+ CheckCast checkCast, InstructionIterator it, IRCode code, Set<Value> affectedValues) {
Value inValue = checkCast.object();
Value outValue = checkCast.outValue();
DexType castType = checkCast.getType();
@@ -2076,6 +2098,7 @@
// A a = ...
// B b = (B) a;
assert inTypeLattice.lessThanOrEqual(outTypeLattice, appView);
+ affectedValues.addAll(outValue.affectedValues());
removeOrReplaceByDebugLocalWrite(checkCast, it, inValue, outValue);
return true;
}
@@ -2167,13 +2190,14 @@
}
}
if (result != InstanceOfResult.UNKNOWN) {
- it.replaceCurrentInstruction(
+ ConstNumber newInstruction =
new ConstNumber(
new Value(
code.valueNumberGenerator.next(),
TypeLatticeElement.INT,
instanceOf.outValue().getLocalInfo()),
- result == InstanceOfResult.TRUE ? 1 : 0));
+ result == InstanceOfResult.TRUE ? 1 : 0);
+ it.replaceCurrentInstruction(newInstruction);
return true;
}
return false;
diff --git a/src/test/java/com/android/tools/r8/ir/optimize/checkcast/CheckCastRemovalTest.java b/src/test/java/com/android/tools/r8/ir/optimize/checkcast/CheckCastRemovalTest.java
index 83890de..aa58df7 100644
--- a/src/test/java/com/android/tools/r8/ir/optimize/checkcast/CheckCastRemovalTest.java
+++ b/src/test/java/com/android/tools/r8/ir/optimize/checkcast/CheckCastRemovalTest.java
@@ -218,7 +218,6 @@
}
@Test
- @Ignore("b/133739171")
public void bothUpAndDowncast() throws Exception {
JasminBuilder builder = new JasminBuilder();
ClassBuilder classBuilder = builder.addClass(CLASS_NAME);
