Front-ends like GNAT for Ada sometimes use biased encodings for integral
types. This change creates a new language hook so that the bias
information can make it into the debugging information back-end and
introduces an experimental DWARF attribute to hold it.
include/ChangeLog:
* dwarf2.def (DW_AT_GNU_bias): New attribute.
gcc/ada/ChangeLog:
* gcc-interface/misc.c (gnat_get_type_bias): New.
(LANG_HOOKS_GET_TYPE_BIAS): Redefine macro to implement the
get_type_bias language hook.
gcc/ChangeLog:
* langhooks.h (struct lang_hooks_for_types): New get_bias_field.
* langhooks-def.h (LANG_HOOKS_GET_TYPE_BIAS): New.
(LANG_HOOKS_FOR_TYPES_INITIALIZER): Initialize the
get_bias_field.
* dwarf2out.c
(base_type_die): In non-strict DWARF mode, invoke the
get_type_bias language hook for INTEGER_TYPE nodes. If it
returns a bias, emit an attribute for it.
(subrange_type_die): Change signature to handle bias. If
non-strict DWARF mode, emit an attribute for it, if one passed.
(modified_type_die): For subrange types, invoke the
get_type_bias langage hook and pass the bias to
subrange_type_die.
--
Pierre-Marie de Rodat
>From 702af856454dd74dc23979e488d311ea008981ee Mon Sep 17 00:00:00 2001
From: Pierre-Marie de Rodat <dero...@adacore.com>
Date: Thu, 8 Jan 2015 11:07:06 +0100
Subject: [PATCH 7/8] DWARF: add a language hook for scalar biased types
Front-ends like GNAT for Ada sometimes use biased encodings for integral
types. This change creates a new language hook so that the bias
information can make it into the debugging information back-end and
introduces an experimental DWARF attribute to hold it.
include/ChangeLog:
* dwarf2.def (DW_AT_GNU_bias): New attribute.
gcc/ada/ChangeLog:
* gcc-interface/misc.c (gnat_get_type_bias): New.
(LANG_HOOKS_GET_TYPE_BIAS): Redefine macro to implement the
get_type_bias language hook.
gcc/ChangeLog:
* langhooks.h (struct lang_hooks_for_types): New get_bias_field.
* langhooks-def.h (LANG_HOOKS_GET_TYPE_BIAS): New.
(LANG_HOOKS_FOR_TYPES_INITIALIZER): Initialize the
get_bias_field.
* dwarf2out.c
(base_type_die): In non-strict DWARF mode, invoke the
get_type_bias language hook for INTEGER_TYPE nodes. If it
returns a bias, emit an attribute for it.
(subrange_type_die): Change signature to handle bias. If
non-strict DWARF mode, emit an attribute for it, if one passed.
(modified_type_die): For subrange types, invoke the
get_type_bias langage hook and pass the bias to
subrange_type_die.
---
gcc/ada/gcc-interface/misc.c | 12 ++++++++++++
gcc/dwarf2out.c | 27 ++++++++++++++++++++++++---
gcc/langhooks-def.h | 2 ++
gcc/langhooks.h | 5 +++++
include/dwarf2.def | 2 ++
5 files changed, 45 insertions(+), 3 deletions(-)
diff --git a/gcc/ada/gcc-interface/misc.c b/gcc/ada/gcc-interface/misc.c
index 4a355a3..47a8b1c 100644
--- a/gcc/ada/gcc-interface/misc.c
+++ b/gcc/ada/gcc-interface/misc.c
@@ -969,6 +969,16 @@ gnat_get_subrange_bounds (const_tree gnu_type, tree *lowval, tree *highval)
*highval = TYPE_MAX_VALUE (gnu_type);
}
+static tree
+gnat_get_type_bias (const_tree gnu_type)
+{
+ if (TREE_CODE (gnu_type) == INTEGER_TYPE
+ && TYPE_BIASED_REPRESENTATION_P (gnu_type)
+ && gnat_encodings == DWARF_GNAT_ENCODINGS_MINIMAL)
+ return TYPE_RM_MIN_VALUE(gnu_type);
+ return NULL_TREE;
+}
+
/* GNU_TYPE is the type of a subprogram parameter. Determine if it should be
passed by reference by default. */
@@ -1268,6 +1278,8 @@ get_lang_specific (tree node)
#define LANG_HOOKS_GET_ARRAY_DESCR_INFO gnat_get_array_descr_info
#undef LANG_HOOKS_GET_SUBRANGE_BOUNDS
#define LANG_HOOKS_GET_SUBRANGE_BOUNDS gnat_get_subrange_bounds
+#undef LANG_HOOKS_GET_TYPE_BIAS
+#define LANG_HOOKS_GET_TYPE_BIAS gnat_get_type_bias
#undef LANG_HOOKS_DESCRIPTIVE_TYPE
#define LANG_HOOKS_DESCRIPTIVE_TYPE gnat_descriptive_type
#undef LANG_HOOKS_GET_DEBUG_TYPE
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index d989264..c38f40f 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -3246,7 +3246,7 @@ static void output_line_info (bool);
static void output_file_names (void);
static dw_die_ref base_type_die (tree);
static int is_base_type (tree);
-static dw_die_ref subrange_type_die (tree, tree, tree, dw_die_ref);
+static dw_die_ref subrange_type_die (tree, tree, tree, tree, dw_die_ref);
static int decl_quals (const_tree);
static dw_die_ref modified_type_die (tree, int, dw_die_ref);
static dw_die_ref generic_parameter_die (tree, tree, bool, dw_die_ref);
@@ -10755,6 +10755,7 @@ base_type_die (tree type)
enum dwarf_type encoding;
bool fpt_used = false;
struct fixed_point_type_info fpt_info;
+ tree type_bias = NULL_TREE;
if (TREE_CODE (type) == ERROR_MARK || TREE_CODE (type) == VOID_TYPE)
return 0;
@@ -10805,6 +10806,10 @@ base_type_die (tree type)
encoding = DW_ATE_unsigned;
else
encoding = DW_ATE_signed;
+
+ if (!dwarf_strict
+ && lang_hooks.types.get_type_bias)
+ type_bias = lang_hooks.types.get_type_bias (type);
break;
case REAL_TYPE:
@@ -10890,6 +10895,12 @@ base_type_die (tree type)
gcc_unreachable ();
}
}
+ if (type_bias != NULL)
+ add_scalar_info (base_type_result, DW_AT_GNU_bias, type_bias,
+ dw_scalar_form_constant
+ | dw_scalar_form_exprloc
+ | dw_scalar_form_reference,
+ NULL);
add_pubtype (type, base_type_result);
return base_type_result;
@@ -10991,7 +11002,8 @@ offset_int_type_size_in_bits (const_tree type)
to a DIE that describes the given type. */
static dw_die_ref
-subrange_type_die (tree type, tree low, tree high, dw_die_ref context_die)
+subrange_type_die (tree type, tree low, tree high, tree bias,
+ dw_die_ref context_die)
{
dw_die_ref subrange_die;
const HOST_WIDE_INT size_in_bytes = int_size_in_bytes (type);
@@ -11012,6 +11024,12 @@ subrange_type_die (tree type, tree low, tree high, dw_die_ref context_die)
add_bound_info (subrange_die, DW_AT_lower_bound, low, NULL);
if (high)
add_bound_info (subrange_die, DW_AT_upper_bound, high, NULL);
+ if (bias && !dwarf_strict)
+ add_scalar_info (subrange_die, DW_AT_GNU_bias, bias,
+ dw_scalar_form_constant
+ | dw_scalar_form_exprloc
+ | dw_scalar_form_reference,
+ NULL);
return subrange_die;
}
@@ -11216,7 +11234,10 @@ modified_type_die (tree type, int cv_quals, dw_die_ref context_die)
&& TREE_TYPE (type) != NULL_TREE
&& subrange_type_for_debug_p (type, &low, &high))
{
- mod_type_die = subrange_type_die (type, low, high, context_die);
+ tree bias = NULL_TREE;
+ if (lang_hooks.types.get_type_bias)
+ bias = lang_hooks.types.get_type_bias (type);
+ mod_type_die = subrange_type_die (type, low, high, bias, context_die);
item_type = TREE_TYPE (type);
}
else if (is_base_type (type))
diff --git a/gcc/langhooks-def.h b/gcc/langhooks-def.h
index 2d02bf6..db96e91 100644
--- a/gcc/langhooks-def.h
+++ b/gcc/langhooks-def.h
@@ -173,6 +173,7 @@ extern tree lhd_make_node (enum tree_code);
#define LANG_HOOKS_TYPE_HASH_EQ NULL
#define LANG_HOOKS_GET_ARRAY_DESCR_INFO NULL
#define LANG_HOOKS_GET_SUBRANGE_BOUNDS NULL
+#define LANG_HOOKS_GET_TYPE_BIAS NULL
#define LANG_HOOKS_DESCRIPTIVE_TYPE NULL
#define LANG_HOOKS_RECONSTRUCT_COMPLEX_TYPE reconstruct_complex_type
#define LANG_HOOKS_ENUM_UNDERLYING_BASE_TYPE lhd_enum_underlying_base_type
@@ -195,6 +196,7 @@ extern tree lhd_make_node (enum tree_code);
LANG_HOOKS_TYPE_HASH_EQ, \
LANG_HOOKS_GET_ARRAY_DESCR_INFO, \
LANG_HOOKS_GET_SUBRANGE_BOUNDS, \
+ LANG_HOOKS_GET_TYPE_BIAS, \
LANG_HOOKS_DESCRIPTIVE_TYPE, \
LANG_HOOKS_RECONSTRUCT_COMPLEX_TYPE, \
LANG_HOOKS_ENUM_UNDERLYING_BASE_TYPE, \
diff --git a/gcc/langhooks.h b/gcc/langhooks.h
index 64ba41f..9dda629 100644
--- a/gcc/langhooks.h
+++ b/gcc/langhooks.h
@@ -127,6 +127,11 @@ struct lang_hooks_for_types
/* Fill in information for the debugger about the bounds of TYPE. */
void (*get_subrange_bounds) (const_tree, tree *, tree *);
+ /* Called on INTEGER_TYPEs. Return NULL_TREE for non-biased types. For
+ biased types, return as an INTEGER_CST node the value that is represented
+ by a physical zero. */
+ tree (*get_type_bias) (const_tree);
+
/* A type descriptive of TYPE's complex layout generated to help the
debugger to decode variable-length or self-referential constructs.
This is only used for the AT_GNAT_descriptive_type DWARF attribute. */
diff --git a/include/dwarf2.def b/include/dwarf2.def
index c5b84f2..dd5c8c1 100644
--- a/include/dwarf2.def
+++ b/include/dwarf2.def
@@ -409,6 +409,8 @@ DW_AT (DW_AT_GNAT_descriptive_type, 0x2302)
/* Rational constant extension, not yet specified. */
DW_TAG (DW_AT_GNU_numerator, 0x2303)
DW_TAG (DW_AT_GNU_denominator, 0x2304)
+/* Biased integer extension, not yet specified. */
+DW_TAG (DW_AT_GNU_bias, 0x2305)
/* UPC extension. */
DW_AT (DW_AT_upc_threads_scaled, 0x3210)
/* PGI (STMicroelectronics) extensions. */
--
2.4.5
