From d49b9ba6e40683a01c3fbf351c661a501c72ced1 Mon Sep 17 00:00:00 2001
From: Pierre-Marie de Rodat <derodat@adacore.com>
Date: Wed, 25 Feb 2015 14:48:24 +0100
Subject: [PATCH] DWARF: fix loc. descr. generation for DW_AT_static_link
gcc/ChangeLog:
PR debug/53927
* tree-nested.c (finalize_nesting_tree_1): Append a field to
hold the frame base address.
* dwarf2out.c (gen_subprogram_die): Generate for
DW_AT_static_link a location description that computes the value
of this field.
---
gcc/dwarf2out.c | 20 ++++++++++++---
gcc/tree-nested.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++------
2 files changed, 83 insertions(+), 10 deletions(-)
@@ -19113,9 +19113,23 @@ gen_subprogram_die (tree decl, dw_die_ref context_die)
compute_frame_pointer_to_fb_displacement (cfa_fb_offset);
if (fun->static_chain_decl)
- add_AT_location_description
- (subr_die, DW_AT_static_link,
- loc_list_from_tree (fun->static_chain_decl, 2, NULL));
+ {
+ /* DWARF requires here a location expression that computes the
+ address of the enclosing subprogram's frame base. The machinery
+ in tree-nested.c is supposed to store this specific address in the
+ last field of the FRAME record. */
+ const tree frame_type
+ = TREE_TYPE (TREE_TYPE (fun->static_chain_decl));
+ const tree fb_decl = tree_last (TYPE_FIELDS (frame_type));
+
+ tree fb_expr
+ = build1 (INDIRECT_REF, frame_type, fun->static_chain_decl);
+ fb_expr = build3 (COMPONENT_REF, TREE_TYPE (fb_decl),
+ fb_expr, fb_decl, NULL_TREE);
+
+ add_AT_location_description (subr_die, DW_AT_static_link,
+ loc_list_from_tree (fb_expr, 0, NULL));
+ }
}
/* Generate child dies for template paramaters. */
@@ -2718,10 +2718,10 @@ fold_mem_refs (tree *const &e, void *data ATTRIBUTE_UNUSED)
return true;
}
-/* Do "everything else" to clean up or complete state collected by the
- various walking passes -- lay out the types and decls, generate code
- to initialize the frame decl, store critical expressions in the
- struct function for rtl to find. */
+/* Do "everything else" to clean up or complete state collected by the various
+ walking passes -- create a field to hold the frame base address, lay out the
+ types and decls, generate code to initialize the frame decl, store critical
+ expressions in the struct function for rtl to find. */
static void
finalize_nesting_tree_1 (struct nesting_info *root)
@@ -2737,16 +2737,75 @@ finalize_nesting_tree_1 (struct nesting_info *root)
out at this time. */
if (root->frame_type)
{
+ int save_warn_padded;
+ tree *adjust, *field_decl_p;
+ char *name;
+ tree fb_decl, fb_ref, fb_tmp;
+ gcall *fb_gimple;
+ gimple_stmt_iterator gsi;
+
+ /* Debugging information needs to compute the frame base address of the
+ nestee frame out of the static chain from the nested frame.
+
+ The static chain is the address of the FRAME record, so one could
+ imagine it would be possible to compute the frame base address just
+ adding a constant offset to this address. Unfortunately, this is not
+ possible: if the FRAME object has alignment constraints that are
+ stronger than the stack, then the offset between the frame base and
+ the FRAME object will be dynamic.
+
+ What we do instead is to append a field to the FRAME object that holds
+ the frame base address: then debug. info. just has to fetch this
+ field. */
+
+ /* Debugging information will refer to the CFA as the frame base
+ address: we will do the same here. */
+ const tree frame_addr_fndecl
+ = builtin_decl_explicit (BUILT_IN_DWARF_CFA);
+
+ /* Create a field in the FRAME record to hold the frame base address for
+ this stack frame. Since it will be used only by the debugger (through
+ the debugging information), put it at the end of the record not to
+ shift all other offsets. */
+ fb_decl = make_node (FIELD_DECL);
+ name = concat ("FRAME_BASE.",
+ IDENTIFIER_POINTER (DECL_NAME (root->context)),
+ NULL);
+ DECL_NAME (fb_decl) = get_identifier (name);
+ free (name);
+ TREE_TYPE (fb_decl) = ptr_type_node;
+ TREE_ADDRESSABLE (fb_decl) = 1;
+ DECL_CONTEXT (fb_decl) = root->frame_type;
+ field_decl_p = &TYPE_FIELDS (root->frame_type);
+ while (*field_decl_p != NULL_TREE)
+ field_decl_p = &DECL_CHAIN (*field_decl_p);
+ *field_decl_p = fb_decl;
+
/* In some cases the frame type will trigger the -Wpadded warning.
This is not helpful; suppress it. */
- int save_warn_padded = warn_padded;
- tree *adjust;
-
+ save_warn_padded = warn_padded;
warn_padded = 0;
layout_type (root->frame_type);
warn_padded = save_warn_padded;
layout_decl (root->frame_decl, 0);
+ /* Initialize the frame base address field. If the builtin we need is
+ not available, set it to NULL so that debugging information does not
+ reference junk. */
+ fb_ref = build3 (COMPONENT_REF, TREE_TYPE (fb_decl),
+ root->frame_decl, fb_decl, NULL_TREE);
+ if (frame_addr_fndecl != NULL_TREE)
+ {
+ fb_gimple = gimple_build_call (frame_addr_fndecl, 1,
+ integer_zero_node);
+ gsi = gsi_last (stmt_list);
+ fb_tmp = init_tmp_var_with_call (root, &gsi, fb_gimple);
+ }
+ else
+ fb_tmp = build_int_cst (TREE_TYPE (fb_ref), 0);
+ gimple_seq_add_stmt (&stmt_list,
+ gimple_build_assign (fb_ref, fb_tmp));
+
/* Remove root->frame_decl from root->new_local_var_chain, so
that we can declare it also in the lexical blocks, which
helps ensure virtual regs that end up appearing in its RTL
--
2.3.3.199.g52cae64