[M3devel] m3cc static chain stuff
Tony Hosking
hosking at cs.purdue.edu
Wed May 26 16:28:51 CEST 2010
We should endeavour to use the same functionality that the C compiler uses for its own nested functions, whereever possible. The only thing is that we also build closures, so the trampoline mechanisms should be avoided.
Antony Hosking | Associate Professor | Computer Science | Purdue University
305 N. University Street | West Lafayette | IN 47907 | USA
Office +1 765 494 6001 | Mobile +1 765 427 5484
On 26 May 2010, at 02:05, Jay K wrote:
>
> Can any of this be removed?
> Can we really not just use "unfold-nested-procs" like NT386?
> We'd just lose a little bit of optimization, in rare cases, stop paying a bad cost/benefit ratio?
> Part of this is actually *deoptimization*. If the compiler decides the values aren't used, then it should
> be allowed to remove them. That is normal. Wanting to unused stuff in the debugger isn't
> generally a considered the responsibility of optimizers.
>
> Therefore -- we could "unfold", remove our diffs, and gain some optimization and some deoptimization.
> Maybe I'll try without.
>
>
> diff -ur /src/orig/gcc-4.3.0/gcc/tree-nested.c /dev2/cm3/m3-sys/m3cc/gcc/gcc/tree-nested.c
> --- /src/orig/gcc-4.3.0/gcc/tree-nested.c 2008-02-15 09:36:43.000000000 -0800
> +++ /dev2/cm3/m3-sys/m3cc/gcc/gcc/tree-nested.c 2010-05-09 22:27:58.000000000 -0700
>
>
> -/* Build or return the RECORD_TYPE that describes the frame state that is
> - shared between INFO->CONTEXT and its nested functions. This record will
> - not be complete until finalize_nesting_tree; up until that point we'll
> +/* This must agree with the string defined by the same name in m3gdb, file
> + m3-util.c */
> +static const char * nonlocal_var_rec_name = "_nonlocal_var_rec";
> +
> +/* Build or return the RECORD_TYPE that describes the non-local frame struct
> + that is shared between INFO->CONTEXT and its nested functions. This record
> + will not be complete until finalize_nesting_tree; up until that point we'll
> be adding fields as necessary.
>
> We also build the DECL that represents this frame in the function. */
> @@ -209,7 +224,8 @@
> free (name);
>
> info->frame_type = type;
> - info->frame_decl = create_tmp_var_for (info, type, "FRAME");
> + info->frame_decl
> + = create_tmp_var_for (info, type, nonlocal_var_rec_name);
>
> /* ??? Always make it addressable for now, since it is meant to
> be pointed to by the static chain pointer. This pessimizes
> @@ -218,6 +234,8 @@
> reachable, but the true pessimization is to create the non-
> local frame structure in the first place. */
> TREE_ADDRESSABLE (info->frame_decl) = 1;
> + /* m3gdb needs to know about this variable. */
> + DECL_IGNORED_P (info->frame_decl) = 0;
> }
> return type;
> }
> @@ -290,6 +308,10 @@
> return *slot;
> }
>
> +/* This must agree with the string defined by the same name in m3gdb, file
> + m3_util.c */
> +static const char * static_link_var_name = "_static_link_var";
> +
> /* Build or return the variable that holds the static chain within
> INFO->CONTEXT. This variable may only be used within INFO->CONTEXT. */
>
> @@ -310,9 +332,14 @@
> Note also that it's represented as a parameter. This is more
> close to the truth, since the initial value does come from
> the caller. */
> - decl = build_decl (PARM_DECL, create_tmp_var_name ("CHAIN"), type);
> + decl = build_decl
> + (PARM_DECL, get_identifier (static_link_var_name), type);
> + TREE_CHAIN (decl) = NULL; /* Possibly redundant, but dbxout needs it. */
> DECL_ARTIFICIAL (decl) = 1;
> - DECL_IGNORED_P (decl) = 1;
> +
> + /* m3gdb needs to know about this variable. */
> + DECL_IGNORED_P (decl) = 0;
> +
> TREE_USED (decl) = 1;
> DECL_CONTEXT (decl) = info->context;
> DECL_ARG_TYPE (decl) = type;
> @@ -326,7 +353,11 @@
> return decl;
> }
>
> -/* Build or return the field within the non-local frame state that holds
> +/* This must agree with the string defined by the same name in m3gdb, file
> + m3_util.c */
> +static const char * static_link_copy_field_name = "_static_link_copy_field";
> +
> +/* Build or return the field within the non-local frame struct that holds
> the static chain for INFO->CONTEXT. This is the way to walk back up
> multiple nesting levels. */
>
> @@ -339,10 +370,12 @@
> tree type = build_pointer_type (get_frame_type (info->outer));
>
> field = make_node (FIELD_DECL);
> - DECL_NAME (field) = get_identifier ("__chain");
> + DECL_NAME (field) = get_identifier (static_link_copy_field_name);
> TREE_TYPE (field) = type;
> DECL_ALIGN (field) = TYPE_ALIGN (type);
> DECL_NONADDRESSABLE_P (field) = 1;
> + /* m3gdb should know about this field. */
> + DECL_IGNORED_P (field) = 0;
>
> insert_field_into_struct (get_frame_type (info), field);
>
> @@ -465,7 +498,7 @@
> return *slot;
> }
>
> -/* Build or return the field within the non-local frame state that holds
> +/* Build or return the field within the non-local frame struct that holds
> the non-local goto "jmp_buf". The buffer itself is maintained by the
> rtl middle-end as dynamic stack space is allocated. */
>
> @@ -1620,6 +1653,9 @@
> switch (TREE_CODE (t))
> {
> case ADDR_EXPR:
> + if (TREE_STATIC (t))
> + break;
> +
> /* Build
> T.1 = &CHAIN->tramp;
> T.2 = __builtin_adjust_trampoline (T.1);
> @@ -1714,6 +1750,22 @@
> }
> break;
>
> + case STATIC_CHAIN_EXPR:
> + decl = TREE_OPERAND (t, 0);
> + target_context = decl_function_context (decl);
> + if (target_context)
> + {
> + if (info->context == target_context)
> + {
> + /* Make sure frame_decl gets created. */
> + (void) get_frame_type (info);
> + }
> + *tp = get_static_chain (info, target_context, &wi->tsi);
> + }
> + else
> + *tp = null_pointer_node;
> + break;
> +
> case RETURN_EXPR:
> case GIMPLE_MODIFY_STMT:
> case WITH_SIZE_EXPR:
> @@ -1768,13 +1820,22 @@
> return NULL_TREE;
> }
>
> +static bool
> +debug_static_links (void)
> +{ return
> + write_symbols != NO_DEBUG
> + && debug_info_level != DINFO_LEVEL_NONE
> + && debug_info_level != DINFO_LEVEL_TERSE;
> +
> +} /* debug_static_links */
> +
> /* Walk the nesting tree starting with ROOT, depth first. Convert all
> trampolines and call expressions. On the way back up, determine if
> a nested function actually uses its static chain; if not, remember that. */
>
> static void
> convert_all_function_calls (struct nesting_info *root)
> -{
> +{
> do
> {
> if (root->inner)
> @@ -1784,7 +1845,10 @@
> walk_function (convert_call_expr, root);
>
> /* If the function does not use a static chain, then remember that. */
> - if (root->outer && !root->chain_decl && !root->chain_field)
> + if (root->outer && !root->chain_decl && !root->chain_field
> +/* REMOVE ME: */
> + /* && !debug_static_links () */
> + )
> DECL_NO_STATIC_CHAIN (root->context) = 1;
> else
> gcc_assert (!DECL_NO_STATIC_CHAIN (root->context));
> @@ -1806,6 +1870,21 @@
> tree context = root->context;
> struct function *sf;
>
> +/* REMOVEME: */
> + /* If this is a nested function and we are supporting debugging via
> + m3gdb, we always need a chain_decl, so m3gdb can find the static
> + chain, even if the programmer's code doesn't use it. */
> + if (false && root->outer && debug_static_links () )
> + { tree static_chain_decl, temp, stmt;
> + /* This is a desperate attempt to get later code generation to
> + store the static link. If it works, it'll be a miracle. */
> + static_chain_decl = get_chain_decl (root);
> + stmt = build_addr (static_chain_decl, root->context);
> + temp = create_tmp_var_for (root, TREE_TYPE (static_chain_decl), NULL);
> + stmt = build_gimple_modify_stmt (temp, static_chain_decl);
> + append_to_statement_list (stmt, &stmt_list);
> + }
> +
> /* If we created a non-local frame type or decl, we need to lay them
> out at this time. */
> if (root->frame_type)
> @@ -1912,7 +1991,7 @@
> proper BIND_EXPR. */
> if (root->new_local_var_chain)
> declare_vars (root->new_local_var_chain, DECL_SAVED_TREE (root->context),
> - false);
> + true);
> if (root->debug_var_chain)
> declare_vars (root->debug_var_chain, DECL_SAVED_TREE (root->context),
> true);
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://m3lists.elegosoft.com/pipermail/m3devel/attachments/20100526/2701e351/attachment-0002.html>
More information about the M3devel
mailing list