Martin Jambor wrote:
Hi,
On Wed, Jan 02, 2008 at 06:13:37PM -0500, Rob Johnson wrote:
I'm experimenting with the gimple plugin infrastructure and I'm having
trouble instrumenting code in a way that is compatible with the optimizer.
Here's a simple example that is intended to insert the function call
"__memcheck_register_argv(argc, argv)" at the beginning of main. The code
runs during pass_plugin_gimple (which comes right after pass_apply_inline
in passes.c) and works great with -O0, but causes the compiler to crash
with -O1 or higher.
-------------------------------------
tree argv_registrar_type;
tree argv_registrar;
tree argv_registrar_call;
argv_registrar_type = build_function_type_list (void_type_node,
integer_type_node,
build_pointer_type
(build_pointer_type
(char_type_node)),
NULL_TREE);
argv_registrar = build_fn_decl ("__memcheck_register_argv",
argv_registrar_type);
argv_registrar_call = build_call_expr (argv_registrar, 2,
DECL_ARGUMENTS (cfun->decl),
TREE_CHAIN (DECL_ARGUMENTS
(cfun->decl)));
DECL_ARGUMENTS is a tree chain of PARM_DECLs and in SSA GIMPLE, scalar
operands (integers and pointer are both scalar, is_gimple_reg()
predicate is there to identify variables that need to be converted to
SSA) need to be SSA_NAMEs of declarations (PARM_DECLs and VAR_DECLs in
particular).
Therefore I suspect you need to create a different chain of respective
SSA_NAMES and pass that to build_call_expr(). You can get the default
SSA_NAME by calling gimple_default_def().
Yes! It seems it's slightly more complicated given that, with some
optimization levels the code is sometimes turned into SSA and sometimes
not, and that, depending on how the original program uses argv and argc,
they may or may not already have default definitions. If the original
program doesn't touch argv/argc, then we also have to update the set of
referenced vars. Here's the code I wrote to construct the argc argument
to the above call expression:
tree argc;
/* If we're doing SSA... */
if (cfun->gimple_df && cfun->gimple_df->default_defs)
{
argc = gimple_default_def (cfun, DECL_ARGUMENTS (cfun->decl));
if (!argc)
{
argc = DECL_ARGUMENTS (cfun->decl);
mark_sym_for_renaming (argc);
}
add_referenced_var (DECL_ARGUMENTS (cfun->decl));
}
else
argc = DECL_ARGUMENTS (cfun->decl);
The code for argv is similar. Does that look right?
Once I get this plugin working, I will try to extract some useful
building blocks for other plugin writers. Thanks for your help!
Best,
Rob
