On 08/31/2015 09:28 AM, Pierre-Marie de Rodat wrote:
Ping for the patch submitted in <https://gcc.gnu.org/ml/gcc-patches/2015-07/msg01629.html>.
As Jason noticed in another thread, I forgot to attach the patch here (although it’s filed in the bug tracker). Here it is! Rebased against trunk, bootstrapped and regtested again on x86_64-linux.
Thanks in advance! -- Pierre-Marie de Rodat
>From d49b9ba6e40683a01c3fbf351c661a501c72ced1 Mon Sep 17 00:00:00 2001 From: Pierre-Marie de Rodat <dero...@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(-) diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c index f184750..5249fca 100644 --- a/gcc/dwarf2out.c +++ b/gcc/dwarf2out.c @@ -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. */ diff --git a/gcc/tree-nested.c b/gcc/tree-nested.c index 1f6311c..06484a2 100644 --- a/gcc/tree-nested.c +++ b/gcc/tree-nested.c @@ -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