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[PATCH] Instance information in DWARF discriminators


The following proposed change adds a new mode of operation where
the discriminator field in DWARF debugging information is set from
information provided by a language front-end to discriminate
between distinct code instances coming from instances of a given
template. (Currently the discriminator is set by assigning
arbitrary distinct identifiers to each basic block associated with
a single source location).

This is intended primarily for the Ada language front-end (further
changes, to be submitted shortly, will enable the new mode of
operation under control of appropriate switches), in order to
allow per-instance source coverage analysis of generics. However
this might also be useful for other language front-ends, e.g. with
C++ templates.

Change tested on x86_64-linux. OK to commit?

2012-08-08  Thomas Quinot  <quinot@adacore.com>

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.
        * tree-cfg.c (assign_discriminator): If flag_debug_instances is set,
        nothing to do here.
	* input.h (LOCATION_INSTANCE): New macro to retrieve instance id.
	* emit-rtl.c (insn_instance): New function to retrieve instance id.
	* rtl.h (insn_instance): Declare.

libcpp/
        * include/line_map.h (struct line_map_ordinary): Add instance field.
        (expanded_location): Ditto.
        (ORDINARY_MAP_INSTANCE): Define.
        * line-map.c (linemap_expand_location): Set instance field in expanded
        location from same in set.

Index: gcc/final.c
===================================================================
--- gcc/final.c	(révision 193884)
+++ gcc/final.c	(copie de travail)
@@ -2894,6 +2894,10 @@
     {
       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 +158,11 @@
 Variable
 int flag_debug_asm
 
+; For generic instances, include complete instantiation chain in debugging
+; information (ELF discriminators).
+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/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/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)
@@ -85,6 +85,12 @@
 
   /* Number of the low-order source_location bits used for a column number.  */
   unsigned int column_bits : 8;
+
+  /* For languages that have the notion of instantiating a given template
+     multiple times, different line_maps can be allocated for each instance,
+     in which case this index identifies the specific instance. Set to 0
+     otherwise.  */
+  int instance;
 };
 
 /* This is the highest possible source location encoded within an
@@ -230,6 +236,9 @@
 #define ORDINARY_MAP_NUMBER_OF_COLUMN_BITS(MAP) \
   linemap_check_ordinary (MAP)->d.ordinary.column_bits
 
+#define ORDINARY_MAP_INSTANCE(MAP) \
+  linemap_check_ordinary (MAP)->d.ordinary.instance
+
 #define MACRO_MAP_MACRO(MAP) (MAP)->d.macro.macro
 
 #define MACRO_MAP_NUM_MACRO_TOKENS(MAP) (MAP)->d.macro.n_tokens
@@ -638,6 +647,9 @@
 
   /* 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(map);
     }
 
   return xloc;

-- 
Thomas Quinot, Ph.D. ** quinot@adacore.com ** Senior Software Engineer
               AdaCore -- Paris, France -- New York, USA


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