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8175883: bytecode generated for the enhanced for loop may block memory garbage collecting
authorvromero
Mon, 20 Nov 2017 17:07:21 -0500
changeset 47864 e29ae57c6421
parent 47863 abe64cd683a4
child 47865 53440b6353b6
8175883: bytecode generated for the enhanced for loop may block memory garbage collecting Reviewed-by: mcimadamore
src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Lower.java file | annotate | diff | comparison | revisions
test/langtools/tools/javac/flow/tests/TestCaseForEach.java file | annotate | diff | comparison | revisions 
--- a/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Lower.java	Mon Nov 20 14:45:11 2017 -0500
+++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Lower.java	Mon Nov 20 17:07:21 2017 -0500
@@ -3226,7 +3226,7 @@
             JCVariableDecl indexdef = make.VarDef(index, make.Literal(INT, 0));
             indexdef.init.type = indexdef.type = syms.intType.constType(0);
 
-            List<JCStatement> loopinit = List.of(arraycachedef, lencachedef, indexdef);
+            List<JCStatement> loopinit = List.of(lencachedef, indexdef);
             JCBinary cond = makeBinary(LT, make.Ident(index), make.Ident(lencache));
 
             JCExpressionStatement step = make.Exec(makeUnary(PREINC, make.Ident(index)));
@@ -3236,18 +3236,27 @@
                                                     make.Ident(index)).setType(elemtype);
             JCVariableDecl loopvardef = (JCVariableDecl)make.VarDef(tree.var.mods,
                                                   tree.var.name,
-                                                  tree.var.vartype,
-                                                  loopvarinit).setType(tree.var.type);
+                                                  tree.var.vartype, null).setType(tree.var.type);
             loopvardef.sym = tree.var.sym;
+
+            JCStatement loopVarAssign = make.Assignment(tree.var.sym, loopvarinit);
             JCBlock body = make.
-                Block(0, List.of(loopvardef, tree.body));
-
+                Block(0, List.of(loopVarAssign, tree.body));
+
+            arraycachedef = translate(arraycachedef);
             result = translate(make.
                                ForLoop(loopinit,
                                        cond,
                                        List.of(step),
                                        body));
             patchTargets(body, tree, result);
+            JCStatement nullAssignToArr = make.Assignment(arraycache, make.Literal(BOT, null).setType(syms.botType));
+            JCStatement nullAssignToLoopVar = tree.var.type.isPrimitive() ?
+                    null :
+                    make.Assignment(tree.var.sym, make.Literal(BOT, null).setType(syms.botType));
+            result = nullAssignToLoopVar == null ?
+                    make.Block(0, List.of(arraycachedef, loopvardef, (JCStatement)result, nullAssignToArr)):
+                    make.Block(0, List.of(arraycachedef, loopvardef, (JCStatement)result, nullAssignToArr, nullAssignToLoopVar));
         }
         /** Patch up break and continue targets. */
         private void patchTargets(JCTree body, final JCTree src, final JCTree dest) {
@@ -3322,16 +3331,25 @@
             JCVariableDecl indexDef = (JCVariableDecl)make.VarDef(tree.var.mods,
                                                   tree.var.name,
                                                   tree.var.vartype,
-                                                  vardefinit).setType(tree.var.type);
+                                                  null).setType(tree.var.type);
             indexDef.sym = tree.var.sym;
-            JCBlock body = make.Block(0, List.of(indexDef, tree.body));
+            JCStatement loopVarAssign = make.Assignment(tree.var.sym, vardefinit);
+            JCBlock body = make.Block(0, List.of(loopVarAssign, tree.body));
             body.endpos = TreeInfo.endPos(tree.body);
+            init = translate(init);
             result = translate(make.
-                ForLoop(List.of(init),
+                ForLoop(List.nil(),
                         cond,
                         List.nil(),
                         body));
             patchTargets(body, tree, result);
+            JCStatement nullAssignToIterator = make.Assignment(itvar, make.Literal(BOT, null).setType(syms.botType));
+            JCStatement nullAssignToLoopVar = tree.var.type.isPrimitive() ?
+                    null :
+                    make.Assignment(tree.var.sym, make.Literal(BOT, null).setType(syms.botType));
+            result = nullAssignToLoopVar == null ?
+                    make.Block(0, List.of(init, indexDef, (JCStatement)result, nullAssignToIterator)):
+                    make.Block(0, List.of(init, indexDef, (JCStatement)result, nullAssignToIterator, nullAssignToLoopVar));
         }
 
     public void visitVarDef(JCVariableDecl tree) {
--- a/test/langtools/tools/javac/flow/tests/TestCaseForEach.java	Mon Nov 20 14:45:11 2017 -0500
+++ b/test/langtools/tools/javac/flow/tests/TestCaseForEach.java	Mon Nov 20 17:07:21 2017 -0500
@@ -3,7 +3,7 @@
 public class TestCaseForEach {
 
     @AliveRange(varName="o", bytecodeStart=25, bytecodeLength=11)
-    @AliveRange(varName="o", bytecodeStart=39, bytecodeLength=1)
+    @AliveRange(varName="o", bytecodeStart=44, bytecodeLength=1)
     void m(String[] args) {
         Object o;
         for (String s : args) {
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