Fixes a missing flow in DataflowOptimizer that might cause incorrect code.

The DataflowOptimizer was building an incorrect control flow graph in the case
that a catch block ended in a throw (in all paths) and a finally block was
also present. In this case the graph would be missing the flow from the end
of the catch block to the finally block.

An example snippet that would be optimized incorrectly is

Object o = null;
try {
if (b) throw new Exception();
k++;
} catch (Exception e) {
o = e;
throw e;
} finally {
if (o == null) {
j++;
}
}

where the optimizer would assume that o is always null at the finally block
and thus transform the code into:

Object o = null;
try {
if (b) throw new Exception();
k++;
} catch (Exception e) {
o = e;
throw e;
} finally {
j++;
}

Fixes issue 8115.

Change-Id: I608bd25157eb0c76ac771697ca70756751c10750
Review-Link: https://gwt-review.googlesource.com/#/c/2600/


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@11602 8db76d5a-ed1c-0410-87a9-c151d255dfc7

Author: rluble@google.com

dev/core/src/com/google/gwt/dev/jjs/impl/gflow/cfg/CfgBuilder.java

@@ -946,13 +946,11 @@ public boolean visit(JTryStatement x, Context ctx) {
         // then the try statement completes abruptly for the same reason.
         for (List<Exit> exits : catchExits) {
           for (Exit e : exits) {
-            // If the catch block completes normally, then the finally block is
+            // If the catch block completes normally or abruptly, then the finally block is
             // executed.
-            if (e.isNormal()) {
-              addEdge(e, finallyNode);
-            } else {
-              // If the catch block completes abruptly for reason R, then the
-              // finally block is executed. Then there is a choice:
+            addEdge(e, finallyNode);
+            if (!e.isNormal()) {
+              // If the catch block completes abruptly for reason R there is a choice:
               for (Exit finallyExit : finallyExits) {
                 if (finallyExit.isNormal()) {
                   // If the finally block completes normally, then the try

dev/core/test/com/google/gwt/dev/jjs/impl/gflow/DataflowOptimizerTest.java

@@ -55,6 +55,39 @@ public void testLinearStatements3() throws Exception {
         "int i; int j; foo(1);");
   }
 
+  /**
+   * Test case for issue 8115 (http://code.google.com/p/google-web-toolkit/issues/detail?id=8115)
+   * @throws Exception
+   */
+  public void testCatchThrowExceptionFinally() throws Exception {
+    addSnippetClassDecl("static boolean b;");
+    addSnippetClassDecl("static int i;");
+    addSnippetClassDecl("static int j;");
+
+    optimize("void", ""
+        + "Object o = null;"
+        + "try {"
+        + "  if (b) throw new UncheckedException1();"
+        + "} catch (UncheckedException1 e) {"
+        + "  o = e;"
+        + "  throw e;"
+        + "} finally {"
+        + "  if (o == null)"
+        + "    j++;"
+        + "}").into(""
+
+        + "Object o = null;"
+        + "try {"
+        + "  if (b) throw new UncheckedException1();"
+        + "} catch (UncheckedException1 e) {"
+        + "  o = e;"
+        + "  throw e;"
+        + "} finally {"
+        + "  if (o == null)"   // the bug would cause this if to be optimized away as always true.
+        + "    j++;"
+        + "}");
+  }
+
   public void testDeadIfBranch1() throws Exception {
     optimize("void",
         "int i = 1; if (i == 1) { int j = 2; } else { int j = 3; }").into(

dev/core/test/com/google/gwt/dev/jjs/impl/gflow/cfg/CfgBuilderTest.java

@@ -758,7 +758,44 @@ public void testCatchThrowException1() throws Exception {
         );
   }
 
-  public void testCatchThrowUncatchedException() throws Exception {
+  /**
+   * Test case for issue 8115 (http://code.google.com/p/google-web-toolkit/issues/detail?id=8115)
+   * @throws Exception
+   */
+  public void testCatchThrowExceptionFinally() throws Exception {
+    assertCfg("void",
+        "try {",
+        "  if (b) throw uncheckedException2;",
+        "  k++;",
+        "} catch (UncheckedException1 e) {",
+        "  throw e;",
+        "} finally {",
+        "  j++;",
+        "}").is(
+        "BLOCK -> [*]",
+        "TRY -> [*]",
+        "BLOCK -> [*]",
+        "STMT -> [*]",
+        "READ(b) -> [*]",
+        "COND (EntryPoint.b) -> [THEN=*, ELSE=1]",
+        "STMT -> [*]",
+        "READ(uncheckedException2) -> [*]",
+        "THROW -> [2]",
+        "1: STMT -> [*]",
+        "READWRITE(k, null) -> [2]",
+        "BLOCK -> [*]",
+        "STMT -> [*]",
+        "READ(e) -> [*]",
+        "THROW -> [*]",
+        "2: BLOCK -> [*]",
+        "STMT -> [*]",
+        "READWRITE(j, null) -> [*, *, *]",
+        "END"
+    );
+  }
+
+
+  public void testCatchThrowUncaughtException() throws Exception {
     assertCfg("void", 
         "try {",
         "  if (b) throw uncheckedException2;",