[vm] Change try-catch IL representation.

  Previously catch blocks were hanging off the function entry blocks being effectively an alternative entry-point into the function. Now catch blocks are hanging off the try-entry blocks.
  Previously all the variables that are used in the catch block and beyond were declared as parameters to catch block. Now only those that have their definitions not dominating catch entry will become parameters (for example, if a variable is assigned in the try-block, it becomes a parameter to catch block).
  During OSR, if OSR target entry point is inside some try-blocks, then all of corresponding try-entry/catch-blocks are pulled up to the OSR entry forming a chain that ends with a jump to the OSR target entry.

TEST=vm/dart/trycatch*, ci
Change-Id: Iae20c6548d5d65c63be6d7a53c1b0d2adac7ac31
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/356311
Commit-Queue: Alexander Aprelev <[email protected]>
Reviewed-by: Slava Egorov <[email protected]>
Reviewed-by: Alexander Markov <[email protected]>

Author: aam

pkg/vm/lib/testing/il_matchers.dart

@@ -228,6 +228,14 @@ class PrettyPrinter {
       }
       buffer.write('}');
     }
+    if (block['o'] == 'TryEntry') {
+      if (block['tryBody'] != null) {
+        buffer.write(' tryBody: B${block["tryBody"]}');
+      }
+      if (block['catches'] != null) {
+        buffer.write(' catches: B${block["catches"]}');
+      }
+    }
     buffer.writeln();
     for (final instr in block['is'] ?? []) {
       buffer.write('  ');
@@ -485,6 +493,31 @@ class _BlockMatcher implements Matcher {
   }
 }
 
+class _TryBlockMatcher implements Matcher {
+  final String? tryBody;
+  final String? catches;
+  _TryBlockMatcher(this.tryBody, this.catches);
+
+  @override
+  MatchStatus match(Env e, covariant Map<String, dynamic> block) {
+    if (block['o'] != 'TryEntry') {
+      return MatchStatus.fail('Expected TryEntry block, got ${block['o']} '
+          'when matching B${block['b']}');
+    }
+    if (tryBody != null && "B${block['tryBody']}" != tryBody) {
+      return MatchStatus.fail(
+          'Expected tryBody block $tryBody , got B${block['tryBody']} '
+          'when matching B${block['b']}');
+    }
+    if (catches != null && "B${block['catches']}" != catches) {
+      return MatchStatus.fail(
+          'Expected catches block $catches , got B${block['catches']} '
+          'when matching B${block['b']}');
+    }
+    return MatchStatus.matched;
+  }
+}
+
 /// A matcher for instruction's named attributes.
 ///
 /// Attributes are resolved to their indices through [Env.descriptors].
@@ -673,6 +706,10 @@ class Matchers {
     return _BlockMatcher(kind, List<ElementMatcher>.from(body));
   }
 
+  _TryBlockMatcher tryBlock({String? tryBody, String? catches}) {
+    return _TryBlockMatcher(tryBody, catches);
+  }
+
   final _AnyMatcher any = const _AnyMatcher();
 
   // ignore: non_constant_identifier_names

runtime/tests/vm/dart/block_ordering_il_test.dart

@@ -138,6 +138,7 @@ void matchIL$bodyAlwaysThrows(FlowGraph graph) {
   graph.match([
     match.block('Graph'),
     match.block('Function'),
+    match.tryBlock(),
     match.block('CatchBlock'),
     match.block('Join'),
   ], inCodegenBlockOrder: true);

runtime/tests/vm/dart/dynamic_module_pragmas_il_test.dart

@@ -265,21 +265,21 @@ void matchIL$testCallInTryWithControlFlow(FlowGraph graph) {
       'pos' << match.Parameter(index: 1),
       match.CheckStackOverflow(),
       'cid1' << match.LoadClassId('value'),
-      match.Branch(match.TestRange('cid1'), ifTrue: 'B9', ifFalse: 'B10'),
+      match.Branch(match.TestRange('cid1'), ifTrue: 'B10', ifFalse: 'B11'),
     ]),
-    'B9' <<
+    'B10' <<
         match.block('Target', [
           match.MoveArgument('value'),
           'value_length1' << match.DispatchTableCall('cid1'),
-          match.Goto('B11'),
+          match.Goto('B12'),
         ]),
-    'B10' <<
+    'B11' <<
         match.block('Target', [
           match.MoveArgument('value'),
           'value_length2' << match.InstanceCall('value'),
-          match.Goto('B11'),
+          match.Goto('B12'),
         ]),
-    'B11' <<
+    'B12' <<
         match.block('Join', [
           'value_length' << match.Phi('value_length1', 'value_length2'),
           'value_length_unboxed' << match.UnboxInt64('value_length'),
@@ -290,49 +290,50 @@ void matchIL$testCallInTryWithControlFlow(FlowGraph graph) {
         ]),
     'B3' <<
         match.block('Target', [
-          match.Goto('B8'),
+          match.Goto('B9'),
         ]),
     'B4' <<
         match.block('Target', [
           match.Goto('B5'),
         ]),
-    'B5' <<
+    'B5' << match.tryBlock(tryBody: 'B6', catches: 'B8'),
+    'B6' <<
         match.block('Join', [
           'pos_boxed' << match.BoxInt64('pos'),
           'cid2' << match.LoadClassId('value'),
-          match.Branch(match.TestRange('cid2'), ifTrue: 'B12', ifFalse: 'B13'),
+          match.Branch(match.TestRange('cid2'), ifTrue: 'B13', ifFalse: 'B14'),
         ]),
-    'B12' <<
+    'B13' <<
         match.block('Target', [
           match.MoveArgument('value'),
           match.MoveArgument('pos_boxed'),
           'value_substring1' << match.DispatchTableCall('cid2'),
-          match.Goto('B14'),
+          match.Goto('B15'),
         ]),
-    'B13' <<
+    'B14' <<
         match.block('Target', [
           match.MoveArgument('value'),
           match.MoveArgument('pos_boxed'),
           'value_substring2' << match.InstanceCall('value', 'pos_boxed'),
-          match.Goto('B14'),
+          match.Goto('B15'),
         ]),
-    'B14' <<
+    'B15' <<
         match.block('Join', [
           'value_substring' <<
               match.Phi('value_substring1', 'value_substring2'),
           match.MoveArgument('value_substring'),
           match.StaticCall('value_substring'),
-          match.Goto('B6'),
+          match.Goto('B7'),
         ]),
-    'B7' <<
+    'B8' <<
         match.block('CatchBlock', [
-          match.Goto('B6'),
+          match.Goto('B7'),
         ]),
-    'B6' <<
+    'B7' <<
         match.block('Join', [
-          match.Goto('B8'),
+          match.Goto('B9'),
         ]),
-    'B8' <<
+    'B9' <<
         match.block('Join', [
           match.DartReturn(match.any),
         ]),

runtime/tests/vm/dart/eliminate_allocations_il_test.dart

@@ -45,14 +45,15 @@ void matchIL$bar(FlowGraph graph) {
     match.block('Function', [
       match.Goto('B3', skipUntilMatched: false),
     ]),
-    'B3' <<
+    'B3' << match.tryBlock(tryBody: 'B4', catches: 'B7'),
+    'B4' <<
         match.block('Join', [
-          match.Goto('B5', skipUntilMatched: false),
+          match.Goto('B6', skipUntilMatched: false),
         ]),
-    'B5' <<
+    'B6' <<
         match.block('Join', [
           match.DartReturn('c_42'),
         ]),
-    'B6' << match.block('CatchBlock'),
+    'B7' << match.block('CatchBlock'),
   ]);
 }

runtime/tests/vm/dart/hash_map_probes_limit_test.dart

@@ -5,7 +5,7 @@
 // This test verifies that a relatively large program (kernel compiler)
 // can be compiled with --hash_map_probes_limit.
 
-// VMOptions=--hash_map_probes_limit=1000
+// VMOptions=--hash_map_probes_limit=2000
 
 import "package:vm/kernel_front_end.dart";
 

runtime/tests/vm/dart/records_return_value_unboxing_il_test.dart

@@ -179,25 +179,26 @@ void matchIL$testUnboxedRecordInTryCatch(FlowGraph graph) {
     match.block('Graph'),
     match.block('Function', [
       match.CheckStackOverflow(),
-      match.Goto('B1'),
+      match.Goto('B3'),
     ]),
-    'B1' <<
+    'B3' << match.tryBlock(tryBody: 'B4', catches: 'B6'),
+    'B4' <<
         match.block('Join', [
           'v1' << match.StaticCall(),
           'v1_a' << match.ExtractNthOutput('v1', index: 0),
           match.MoveArgument('v1_a'),
           match.StaticCall(),
-          match.Goto('B3'),
+          match.Goto('B5'),
         ]),
-    'B2' <<
+    'B6' <<
         match.block('CatchBlock', [
           'e' << match.Parameter(index: 2),
           'st' << match.Parameter(index: 3),
           match.MoveArgument('e'),
           match.StaticCall(),
-          match.Goto('B3'),
+          match.Goto('B5'),
         ]),
-    'B3' <<
+    'B5' <<
         match.block('Join', [
           match.DartReturn(),
         ]),

runtime/tests/vm/dart/regress_flutter110715_il_test.dart

@@ -44,24 +44,24 @@ void main() async {
 void matchIL$bug1(FlowGraph graph) {
   graph.dump();
   graph.match([
-    match.block('Graph'),
+    match.block('Graph', ['cnull' << match.Constant(value: null)]),
     match.block('Function'),
+    match.block('Try'),
     match.block('Join'),
     match.block('CatchBlock', [
-      'v0' << match.Parameter(),
-      match.Branch(match.StrictCompare('v0', match.any, kind: '==='),
-          ifTrue: 'B6', ifFalse: 'B7'),
+      match.Branch(match.StrictCompare(match.any, 'cnull', kind: '==='),
+          ifTrue: 'B7', ifFalse: 'B8'),
     ]),
-    'B6' <<
+    'B7' <<
         match.block('Target', [
-          match.Goto('B4'),
+          match.Goto('B5'),
         ]),
-    'B7' <<
+    'B8' <<
         match.block('Target', [
           match.ClosureCall(),
-          match.Goto('B4'),
+          match.Goto('B5'),
         ]),
-    'B4' <<
+    'B5' <<
         match.block('Join', [
           match.DartReturn(),
         ]),
@@ -71,24 +71,24 @@ void matchIL$bug1(FlowGraph graph) {
 void matchIL$bug2(FlowGraph graph) {
   graph.dump();
   graph.match([
-    match.block('Graph'),
+    match.block('Graph', ['cnull' << match.Constant(value: null)]),
     match.block('Function'),
+    match.tryBlock(),
     match.block('Join'),
     match.block('CatchBlock', [
-      'v0' << match.Parameter(),
-      match.Branch(match.StrictCompare('v0', match.any, kind: '==='),
-          ifTrue: 'B6', ifFalse: 'B7'),
+      match.Branch(match.StrictCompare(match.any, 'cnull', kind: '==='),
+          ifTrue: 'B7', ifFalse: 'B8'),
     ]),
-    'B6' <<
+    'B7' <<
         match.block('Target', [
-          match.Goto('B4'),
+          match.Goto('B5'),
         ]),
-    'B7' <<
+    'B8' <<
         match.block('Target', [
           match.ClosureCall(),
-          match.Goto('B4'),
+          match.Goto('B5'),
         ]),
-    'B4' <<
+    'B5' <<
         match.block('Join', [
           match.DartReturn(),
         ]),

runtime/tests/vm/dart/trycatch_alias_catch_object_test.dart

@@ -0,0 +1,41 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+//
+// Test that aliasing of thrown exception is handled correctly.
+//
+
+import 'package:expect/expect.dart';
+
+class X {
+  int v = 0;
+}
+
+class Y {
+  final x = X();
+}
+
+void foo() {
+  var y = Y();
+  try {
+    throw y.x;
+  } on X catch (e) {
+    e.v = 10; // e is an alias of y.x
+  }
+  Expect.equals(10, y.x.v); // should be 10 not 0.
+}
+
+void bar() {
+  var o = X();
+  try {
+    throw o;
+  } on X catch (e) {
+    e.v = 10; // e is an alias of o
+  }
+  Expect.equals(10, o.v);
+}
+
+main() {
+  foo();
+  bar();
+}

runtime/tests/vm/dart/trycatch_alias_catch_test.dart

@@ -0,0 +1,41 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+//
+// Ensure that aliasing calculation takes try-catch into account.
+// Otherwise, optimizations like dead store elimination can produce
+// incorrect results.
+//
+
+import 'package:expect/expect.dart';
+
+class C {
+  int v = 0;
+}
+
+@pragma('vm:never-inline')
+void alwaysThrow() {
+  throw 'a';
+}
+
+void foo() {
+  C? alias;
+  final alloc = C();
+  try {
+    alias = alloc;
+    alwaysThrow();
+    alias = null;
+  } catch (e) {}
+  // here [alias] will be aliasing [alloc].
+  // [alias] should be a `Phi(Constant(null), Parameter(...))`
+  // where `Parameter` arrives from the catch entry.
+  alias!.v = 42;
+  // [alloc] should be referencing a AllocateObject
+  // directly here.
+  Expect.equals(42, alloc.v);
+}
+
+void main() {
+  foo();
+}