expr_is_pure() is introduced to distinguish expressions with side effects.
Instances of such expressions should not occure more than once in the tree
or mimic-stack.
Signed-off-by: Tomek Grabiec <tgrab...@gmail.com>
---
include/jit/expression.h | 1 +
jit/expression.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 64 insertions(+), 0 deletions(-)
diff --git a/include/jit/expression.h b/include/jit/expression.h
index c0d420e..0633d6d 100644
--- a/include/jit/expression.h
+++ b/include/jit/expression.h
@@ -314,6 +314,7 @@ struct expression *dup_expr(struct parse_context *, struct
expression *);
unsigned long nr_args(struct expression *);
int expr_nr_kids(struct expression *);
+int expr_is_pure(struct expression *);
static inline int is_invoke_expr(struct expression *expr)
{
diff --git a/jit/expression.c b/jit/expression.c
index 22bfcf4..d46c2b7 100644
--- a/jit/expression.c
+++ b/jit/expression.c
@@ -55,6 +55,69 @@ int expr_nr_kids(struct expression *expr)
}
}
+/**
+ * Returns true if given expression does not have any potential side
+ * effects and hence one instance of this expression can be safely
+ * connected to many nodes in the tree.
+ */
+int expr_is_pure(struct expression *expr)
+{
+ int i;
+
+ switch (expr_type(expr)) {
+ /*
+ * These expressions may or may not have side effects
+ * depending on their actual children expressions. In
+ * general these expressions should not be connected
+ * to more than one node.
+ */
+ case EXPR_BINOP:
+ case EXPR_ARGS_LIST:
+ case EXPR_UNARY_OP:
+ case EXPR_CONVERSION:
+ case EXPR_ARG:
+ case EXPR_ARRAYLENGTH:
+ case EXPR_INSTANCEOF:
+ case EXPR_ARRAY_SIZE_CHECK:
+ case EXPR_MULTIARRAY_SIZE_CHECK:
+ case EXPR_NULL_CHECK:
+
+ /* These expression types should be always assumed to
+ have side-effects. */
+ case EXPR_INVOKE:
+ case EXPR_INVOKEVIRTUAL:
+ case EXPR_NEWARRAY:
+ case EXPR_ANEWARRAY:
+ case EXPR_MULTIANEWARRAY:
+ case EXPR_NEW:
+ return false;
+
+ /* These expression types do not have any side-effects */
+ case EXPR_VALUE:
+ case EXPR_FVALUE:
+ case EXPR_LOCAL:
+ case EXPR_TEMPORARY:
+ case EXPR_CLASS_FIELD:
+ case EXPR_NO_ARGS:
+ case EXPR_EXCEPTION_REF:
+ case EXPR_INSTANCE_FIELD:
+ case EXPR_MIMIC_STACK_SLOT:
+ return true;
+
+ /* EXPR_ARRAY_DEREF can have side effects in general
+ but it can not be copied so it's considered pure
+ when all it's children are pure. */
+ case EXPR_ARRAY_DEREF:
+ for (i = 0; i < expr_nr_kids(expr); i++)
+ if (!expr_is_pure(to_expr(expr->node.kids[i])))
+ return false;
+ return true;
+
+ default:
+ assert(!"Invalid expression type");
+ }
+}
+
struct expression *alloc_expression(enum expression_type type,
enum vm_type vm_type)
{
--
1.6.0.6
------------------------------------------------------------------------------
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