* Tom Tromey, 2012-11-29 :
> Thomas> Now, an alternative might be to have an array of instance IDs stored
> at
> Thomas> the struct line_maps level, with the same indices at the set of
> ordinary
> Thomas> maps, which would be allocated only when flag_debug_instances is used;
> Thomas> when it is not used the cost would then be a single NULL pointer in
> Thomas> struct line_maps. Would that be acceptable?
>
> I thought there was already a similar approach in place.
> See location_adhoc_data.
> The proliferation of ways to do this is mildly worrying.
Tom,
location_adhoc_data is not really appropriate as it associates data with
a single locus, whereas we need an instance identifier for all loci
covered by a given line map entry.
Attached to this message is an update patch based on an alternative
approach, consisting in maintaining the instance ids in a parallel map
that is allocated only when actually used. In this way, the cost when
not using the option is reduced to a single NULL pointer in struct
line_maps.
This change also attempts to better document the new flag, as pointed
out by Richard, and fixes a few style nits. The LTO streaming part is
still missing.
The updated ChangeLog is:
gcc/
* common.opt (flag_debug_instances): Define new internal flag.
* final.c (notice_source_line): If flag_debug_instances is set,
set discriminator to current instance id.
* emit-rtl.c (insn_instance): New subprogram, retrieves instance
identifier from insn.
* rtl.h (insn_instance): Declare.
* input.h (LOCATION_INSTANCE): Define.
* tree-cfg.c (assign_discriminator): If flag_debug_instances is set,
nothing to do here.
libcpp/
* include/line_map.h (struct line_maps): Add instance_ids field
(table for use under flag_debug_instances).
(expanded_location): Add instance id field.
(LINEMAPS_INSTANCE_IDS): Define.
(ORDINARY_MAP_INSTANCE): Define.
* line-map.c (linemap_expand_location): Set instance field in expanded
location from same in set.
Index: gcc/rtl.h
===================================================================
--- gcc/rtl.h (révision 193884)
+++ gcc/rtl.h (copie de travail)
@@ -1917,6 +1917,7 @@
/* In emit-rtl.c */
extern int insn_line (const_rtx);
extern const char * insn_file (const_rtx);
+extern int insn_instance (const_rtx);
extern tree insn_scope (const_rtx);
extern location_t prologue_location, epilogue_location;
Index: gcc/final.c
===================================================================
--- gcc/final.c (révision 193884)
+++ gcc/final.c (copie de travail)
@@ -2894,6 +2894,8 @@
{
filename = insn_file (insn);
linenum = insn_line (insn);
+ if (flag_debug_instances)
+ discriminator = insn_instance (insn);
}
if (filename == NULL)
Index: gcc/input.h
===================================================================
--- gcc/input.h (révision 193884)
+++ gcc/input.h (copie de travail)
@@ -51,6 +51,7 @@
#define LOCATION_FILE(LOC) ((expand_location (LOC)).file)
#define LOCATION_LINE(LOC) ((expand_location (LOC)).line)
#define LOCATION_COLUMN(LOC)((expand_location (LOC)).column)
+#define LOCATION_INSTANCE(LOC) ((expand_location (LOC)).instance)
#define LOCATION_LOCUS(LOC) \
((IS_ADHOC_LOC(LOC)) ? get_location_from_adhoc_loc (line_table, LOC) : (LOC))
#define LOCATION_BLOCK(LOC) \
Index: gcc/emit-rtl.c
===================================================================
--- gcc/emit-rtl.c (révision 193884)
+++ gcc/emit-rtl.c (copie de travail)
@@ -6007,6 +6007,14 @@
return LOCATION_FILE (INSN_LOCATION (insn));
}
+/* Return source instance of the statement that produced this insn. */
+
+int
+insn_instance (const_rtx insn)
+{
+ return LOCATION_INSTANCE (INSN_LOCATION (insn));
+}
+
/* Return true if memory model MODEL requires a pre-operation (release-style)
barrier or a post-operation (acquire-style) barrier. While not universal,
this function matches behavior of several targets. */
Index: gcc/common.opt
===================================================================
--- gcc/common.opt (révision 193884)
+++ gcc/common.opt (copie de travail)
@@ -158,6 +158,15 @@
Variable
int flag_debug_asm
+; Language front-ends that support multiple instantiations of a given
+; source template (such as Ada with generics) may enable this flag, and
+; provide instance identifiers in the line map, so that discriminators in
+; DWARF debugging information carry these instance identifiers, allowing
+; external tools to identify which instance a given object instruction comes
+; from.
+Variable
+int flag_debug_instances = 0
+
; -dP causes the rtl to be emitted as a comment in assembly.
Variable
int flag_dump_rtl_in_asm
Index: gcc/tree-cfg.c
===================================================================
--- gcc/tree-cfg.c (révision 193884)
+++ gcc/tree-cfg.c (copie de travail)
@@ -768,7 +768,7 @@
{
gimple first_in_to_bb, last_in_to_bb;
- if (locus == 0 || bb->discriminator != 0)
+ if (locus == 0 || bb->discriminator != 0 || flag_debug_instances)
return;
first_in_to_bb = first_non_label_stmt (bb);
Index: libcpp/include/line-map.h
===================================================================
--- libcpp/include/line-map.h (révision 193884)
+++ libcpp/include/line-map.h (copie de travail)
@@ -230,6 +230,12 @@
#define ORDINARY_MAP_NUMBER_OF_COLUMN_BITS(MAP) \
linemap_check_ordinary (MAP)->d.ordinary.column_bits
+#define ORDINARY_MAP_INSTANCE(SET,MAP) \
+ (LINEMAPS_INSTANCE_IDS(SET) != NULL ? \
+ LINEMAPS_INSTANCE_IDS(SET)[linemap_check_ordinary (MAP) - \
+ LINEMAPS_ORDINARY_MAP_AT(SET, 0)] : \
+ 0)
+
#define MACRO_MAP_MACRO(MAP) (MAP)->d.macro.macro
#define MACRO_MAP_NUM_MACRO_TOKENS(MAP) (MAP)->d.macro.n_tokens
@@ -291,6 +297,13 @@
struct maps_info info_macro;
+ /* For languages that have the notion of instantiating a given template
+ multiple times, different line_maps can be allocated for each instance,
+ which are distinguished by an instance identifier. When
+ flag_debug_instaces is enabled, this table (which has the same indices
+ as the ordinary linemaps in this set) stores these instance ids. */
+ int * GTY((atomic)) instance_ids;
+
/* Depth of the include stack, including the current file. */
unsigned int depth;
@@ -369,6 +382,11 @@
#define LINEMAPS_ORDINARY_MAPS(SET) \
LINEMAPS_MAPS (SET, false)
+/* Returns the vector of instance identifiers associated to ordinary maps in
+ the line table SET. */
+#define LINEMAPS_INSTANCE_IDS(SET) \
+ (SET)->instance_ids
+
/* Returns the INDEXth ordinary map. */
#define LINEMAPS_ORDINARY_MAP_AT(SET, INDEX) \
LINEMAPS_MAP_AT (SET, false, INDEX)
@@ -638,6 +656,9 @@
/* In a system header?. */
bool sysp;
+
+ /* Instance id. */
+ int instance;
} expanded_location;
/* This is enum is used by the function linemap_resolve_location
Index: libcpp/line-map.c
===================================================================
--- libcpp/line-map.c (révision 193884)
+++ libcpp/line-map.c (copie de travail)
@@ -1395,6 +1395,7 @@
xloc.line = SOURCE_LINE (map, loc);
xloc.column = SOURCE_COLUMN (map, loc);
xloc.sysp = LINEMAP_SYSP (map) != 0;
+ xloc.instance = ORDINARY_MAP_INSTANCE (set, map);
}
return xloc;
