Fix bug in repeated field read elimination.

There's a case that was missing in this optimization. We install invalidation
points on a block's dominance frontiers when the block contains som
invalidation instructions. However, if a block is an entry to exception
handler, state is always invalidated. This should be done
since exception handler may recover and proceed with some code that
follows try/catch block. Without this change code after try/catch inherits
state of `try` block, which is invalid, since `catch` is another
source from where we can get there. We can't rely on regular instruction
analysis in `catch` blocks, since we get into `catch` from an unpredictable
point.

core/src/main/java/org/teavm/model/optimization/RepeatedFieldReadElimination.java

@@ -28,7 +28,9 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Deque;
 import java.util.HashSet;
+import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Objects;
 import java.util.Set;
 import org.teavm.common.DominatorTree;
 import org.teavm.common.Graph;
@@ -40,6 +42,7 @@ import org.teavm.model.FieldReader;
 import org.teavm.model.FieldReference;
 import org.teavm.model.Instruction;
 import org.teavm.model.Program;
+import org.teavm.model.TryCatchBlock;
 import org.teavm.model.analysis.AliasAnalysis;
 import org.teavm.model.instructions.AbstractInstructionVisitor;
 import org.teavm.model.instructions.AssignInstruction;
@@ -316,6 +319,12 @@ public class RepeatedFieldReadElimination implements MethodOptimization {
         int[][] domFrontiers = GraphUtils.findDominanceFrontiers(cfg, dom);
         everythingInvalid = new boolean[program.basicBlockCount()];
         invalidFields.addAll(Collections.nCopies(program.basicBlockCount(), null));
+        boolean[] exceptionHandlers = new boolean[program.basicBlockCount()];
+        for (BasicBlock block : program.getBasicBlocks()) {
+            for (TryCatchBlock tryCatchBlock : block.getTryCatchBlocks()) {
+                exceptionHandlers[tryCatchBlock.getHandler().getIndex()] = true;
+            }
+        }
 
         IntArrayDeque worklist = new IntArrayDeque();
         InstructionAnalyzer instructionAnalyzer = new InstructionAnalyzer();
@@ -325,26 +334,43 @@ public class RepeatedFieldReadElimination implements MethodOptimization {
                 continue;
             }
 
-            for (Instruction instruction : block) {
-                instructionAnalyzer.reset();
-                instruction.acceptVisitor(instructionAnalyzer);
+            Set<FieldAndInstance> fieldsToInvalidate = new LinkedHashSet<>();
+            boolean allInvalid = false;
+            if (exceptionHandlers[block.getIndex()]) {
+                allInvalid = true;
+            } else {
+                for (Instruction instruction : block) {
+                    instructionAnalyzer.reset();
+                    instruction.acceptVisitor(instructionAnalyzer);
 
-                if (instructionAnalyzer.invalidatesAll) {
-                    worklist.addLast(frontiers);
-                    while (!worklist.isEmpty()) {
-                        int target = worklist.removeFirst();
-                        if (!everythingInvalid[target]) {
-                            everythingInvalid[target] = true;
-                            invalidFields.set(target, null);
-                            worklist.addLast(domFrontiers[target]);
-                        }
+                    if (instructionAnalyzer.invalidatesAll) {
+                        allInvalid = true;
+                        fieldsToInvalidate.clear();
+                        break;
+                    } else if (instructionAnalyzer.invalidatedField != null
+                            && !isVolatile(instructionAnalyzer.invalidatedField)) {
+                        fieldsToInvalidate.add(new FieldAndInstance(instructionAnalyzer.invalidatedField,
+                                instructionAnalyzer.instance));
                     }
-                } else if (instructionAnalyzer.invalidatedField != null
-                        && !isVolatile(instructionAnalyzer.invalidatedField)) {
+                }
+            }
+
+            if (allInvalid) {
+                worklist.addLast(frontiers);
+                while (!worklist.isEmpty()) {
+                    int target = worklist.removeFirst();
+                    if (!everythingInvalid[target]) {
+                        everythingInvalid[target] = true;
+                        invalidFields.set(target, null);
+                        worklist.addLast(domFrontiers[target]);
+                    }
+                }
+            } else {
+                for (FieldAndInstance fieldAndInstance : fieldsToInvalidate) {
                     worklist.addLast(frontiers);
 
-                    int instance = instructionAnalyzer.instance;
-                    FieldReference field = instructionAnalyzer.invalidatedField;
+                    int instance = fieldAndInstance.instance;
+                    FieldReference field = fieldAndInstance.field;
 
                     while (!worklist.isEmpty()) {
                         int target = worklist.removeFirst();
@@ -401,4 +427,31 @@ public class RepeatedFieldReadElimination implements MethodOptimization {
             invalidatesAll = true;
         }
     }
+
+    static class FieldAndInstance {
+        final FieldReference field;
+        final int instance;
+
+        FieldAndInstance(FieldReference field, int instance) {
+            this.field = field;
+            this.instance = instance;
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) {
+                return true;
+            }
+            if (!(o instanceof FieldAndInstance)) {
+                return false;
+            }
+            FieldAndInstance that = (FieldAndInstance) o;
+            return instance == that.instance && field.equals(that.field);
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(field, instance);
+        }
+    }
 }

core/src/test/java/org/teavm/model/optimization/test/RepeatedFieldReadEliminationTest.java

@@ -86,6 +86,11 @@ public class RepeatedFieldReadEliminationTest {
         doTest();
     }
 
+    @Test
+    public void readAfterException() {
+        doTest();
+    }
+
     private void doTest() {
         String originalPath = PREFIX + name.getMethodName() + ".original.txt";
         String expectedPath = PREFIX + name.getMethodName() + ".expected.txt";
@@ -127,6 +132,11 @@ public class RepeatedFieldReadEliminationTest {
         getFoo.getModifiers().add(ElementModifier.NATIVE);
         foo.addMethod(getFoo);
 
+        MethodHolder getIntValue = new MethodHolder("getIntValue", ValueType.INTEGER);
+        getIntValue.getModifiers().add(ElementModifier.STATIC);
+        getIntValue.getModifiers().add(ElementModifier.NATIVE);
+        foo.addMethod(getIntValue);
+
         classSource.putClassHolder(foo);
 
         MethodOptimizationContext context = new MethodOptimizationContext() {

core/src/test/resources/model/optimization/repeated-field-read-elimination/readAfterException.expected.txt

@@ -0,0 +1,13 @@
+var @this as this
+
+$start
+  @o := invokeStatic `Foo.getFoo()LFoo;`
+  @v := invokeStatic `Foo.getIntValue()I`
+  field Foo.intField @o := @v as I
+  goto $exit
+  catch java.lang.RuntimeException goto $handler
+$handler
+  goto $exit
+$exit
+  @x := field Foo.intField @o as I
+  return

core/src/test/resources/model/optimization/repeated-field-read-elimination/readAfterException.original.txt

@@ -0,0 +1,13 @@
+var @this as this
+
+$start
+  @o := invokeStatic `Foo.getFoo()LFoo;`
+  @v := invokeStatic `Foo.getIntValue()I`
+  field Foo.intField @o := @v as I
+  goto $exit
+  catch java.lang.RuntimeException goto $handler
+$handler
+  goto $exit
+$exit
+  @x := field Foo.intField @o as I
+  return