Expressions with volatile content should not be pushed onto mimic-stack
because there is a possibility that their content will be modified
before their value is accessed. An example of this situation is this
java snippet:
int x = 0;
int y;
y = x++;
Which compiles to the following instructions:
0: iconst_0
1: istore_1
2: iload_1
3: iinc 1, 1
6: istore_2
Instriction at pc=2 pushes EXPR_LOCAL onto mimic-stack.
Instruction at pc=3 modifies value of local variable.
Instruction at pc=6 generates STMT_STORE with source popped
from mimic-stack (EXPR_LOCAL) which has invalid value - it was
modified while in mimic-stack. The solution for this is to
generate STMT_STORE which copies the value of local variable
into a new temporary at *load bytecodes and push corresponding
EXPR_TEMPORARY on stack.
Signed-off-by: Tomek Grabiec <tgrab...@gmail.com>
---
jit/load-store-bc.c | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/jit/load-store-bc.c b/jit/load-store-bc.c
index ec0036d..9f3e02f 100644
--- a/jit/load-store-bc.c
+++ b/jit/load-store-bc.c
@@ -12,6 +12,7 @@
#include <jit/compiler.h>
#include <jit/statement.h>
+#include <jit/expression.h>
#include <vm/bytecode.h>
#include <vm/bytecodes.h>
@@ -178,13 +179,20 @@ int convert_ldc2_w(struct parse_context *ctx)
static int convert_load(struct parse_context *ctx, unsigned char index, enum
vm_type type)
{
+ struct expression *tmp_expr;
struct expression *expr;
expr = local_expr(type, index);
if (!expr)
return -ENOMEM;
- convert_expression(ctx, expr);
+ tmp_expr = copy_expr_value(ctx, expr);
+ if (!tmp_expr) {
+ expr_put(expr);
+ return -ENOMEM;
+ }
+
+ convert_expression(ctx, tmp_expr);
return 0;
}
--
1.6.0.6
------------------------------------------------------------------------------
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