Re: [PATCH] Instance information in DWARF discriminators

[Richard Biener <richard dot guenther at gmail dot com>]

On Wed, Nov 28, 2012 at 4:46 PM, Thomas Quinot <quinot@adacore.com> wrote:
> 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?

You need to stream the id with LTO, no?  Also increasing the size
of line_map_ordinary might not be the most welcom change ...

Documentation of the flag is missing as well.

Richard.

> 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);
> +        }

no {} braces

>      }
>
>    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