Re: [PATCH v4] btf: Add support to BTF_KIND_ENUM64 type

[Indu Bhagat <indu.bhagat@oracle.com>]

On 10/21/22 2:28 AM, Indu Bhagat via Gcc-patches wrote:
> On 10/19/22 19:05, Guillermo E. Martinez wrote:
>> Hello,
>>
>> The following is patch v4 to update BTF/CTF backend supporting
>> BTF_KIND_ENUM64 type. Changes from v3:
>>
>>    + Remove `ctf_enum_binfo' structure.
>>    + Remove -m{little,big}-endian from dg-options in testcase.
>>
>> Comments will be welcomed and appreciated!,
>>
>> Kind regards,
>> guillermo
>> -- 
>>
> 
> Thanks Guillermo.
> 
> LGTM.
> 

Pushed on behalf of Guillermo.

Thanks

>> BTF supports 64-bits enumerators with following encoding:
>>
>>    struct btf_type:
>>      name_off: 0 or offset to a valid C identifier
>>      info.kind_flag: 0 for unsigned, 1 for signed
>>      info.kind: BTF_KIND_ENUM64
>>      info.vlen: number of enum values
>>      size: 1/2/4/8
>>
>> The btf_type is followed by info.vlen number of:
>>
>>      struct btf_enum64
>>      {
>>        uint32_t name_off;   /* Offset in string section of enumerator 
>> name.  */
>>        uint32_t val_lo32;   /* lower 32-bit value for a 64-bit value 
>> Enumerator */
>>        uint32_t val_hi32;   /* high 32-bit value for a 64-bit value 
>> Enumerator */
>>      };
>>
>> So, a new btf_enum64 structure was added to represent BTF_KIND_ENUM64
>> and a new field dtd_enum_unsigned in ctf_dtdef structure to distinguish
>> when CTF enum is a signed or unsigned type, later that information is
>> used to encode the BTF enum type.
>>
>> gcc/ChangeLog:
>>
>>     * btfout.cc (btf_calc_num_vbytes): Compute enumeration size 
>> depending of
>>     enumerator type btf_enum{,64}.
>>     (btf_asm_type): Update btf_kflag according to enumeration type sign
>>     using dtd_enum_unsigned field for both:  BTF_KIND_ENUM{,64}.
>>     (btf_asm_enum_const): New argument to represent the size of
>>     the BTF enum type, writing the enumerator constant value for
>>     32 bits, if it's 64 bits then explicitly writes lower 32-bits
>>     value and higher 32-bits value.
>>     (output_asm_btf_enum_list): Add enumeration size argument.
>>     * ctfc.cc (ctf_add_enum): New argument to represent CTF enum
>>     basic information.
>>     (ctf_add_generic): Use of ei_{name. size, unsigned} to build the
>>     dtd structure containing enumeration information.
>>     (ctf_add_enumerator): Update comment mention support for BTF
>>     enumeration in 64-bits.
>>     * dwarf2ctf.cc (gen_ctf_enumeration_type): Extract signedness
>>     for enumeration type and use it in ctf_add_enum.
>>     * ctfc.h (ctf_dmdef): Update dmd_value to HOST_WIDE_INT to allow
>>     use 32/64 bits enumerators.
>>     information.
>>     (ctf_dtdef): New field to describe enum signedness.
>>
>> include/
>>     * btf.h (btf_enum64): Add new definition and new symbolic
>>     constant to BTF_KIND_ENUM64 and BTF_KF_ENUM_{UN,}SIGNED.
>>
>> gcc/testsuite/ChangeLog:
>>
>>     * gcc.dg/debug/btf/btf-enum-1.c: Update testcase, with correct
>>     info.kflags encoding.
>>     * gcc.dg/debug/btf/btf-enum64-1.c: New testcase.
>> ---
>>   gcc/btfout.cc                                 | 30 ++++++++++---
>>   gcc/ctfc.cc                                   | 13 +++---
>>   gcc/ctfc.h                                    |  5 ++-
>>   gcc/dwarf2ctf.cc                              |  5 ++-
>>   gcc/testsuite/gcc.dg/debug/btf/btf-enum-1.c   |  2 +-
>>   gcc/testsuite/gcc.dg/debug/btf/btf-enum64-1.c | 44 +++++++++++++++++++
>>   include/btf.h                                 | 19 ++++++--
>>   7 files changed, 100 insertions(+), 18 deletions(-)
>>   create mode 100644 gcc/testsuite/gcc.dg/debug/btf/btf-enum64-1.c
>>
>> diff --git a/gcc/btfout.cc b/gcc/btfout.cc
>> index 997a33fa089..aef9fd70a28 100644
>> --- a/gcc/btfout.cc
>> +++ b/gcc/btfout.cc
>> @@ -223,7 +223,9 @@ btf_calc_num_vbytes (ctf_dtdef_ref dtd)
>>         break;
>>       case BTF_KIND_ENUM:
>> -      vlen_bytes += vlen * sizeof (struct btf_enum);
>> +      vlen_bytes += (dtd->dtd_data.ctti_size == 0x8)
>> +            ? vlen * sizeof (struct btf_enum64)
>> +            : vlen * sizeof (struct btf_enum);
>>         break;
>>       case BTF_KIND_FUNC_PROTO:
>> @@ -622,6 +624,15 @@ btf_asm_type (ctf_container_ref ctfc, 
>> ctf_dtdef_ref dtd)
>>         btf_size_type = 0;
>>       }
>> +  if (btf_kind == BTF_KIND_ENUM)
>> +    {
>> +      btf_kflag = dtd->dtd_enum_unsigned
>> +            ? BTF_KF_ENUM_UNSIGNED
>> +            : BTF_KF_ENUM_SIGNED;
>> +      if (dtd->dtd_data.ctti_size == 0x8)
>> +    btf_kind = BTF_KIND_ENUM64;
>> +   }
>> +
>>     dw2_asm_output_data (4, dtd->dtd_data.ctti_name, "btt_name");
>>     dw2_asm_output_data (4, BTF_TYPE_INFO (btf_kind, btf_kflag, 
>> btf_vlen),
>>                  "btt_info: kind=%u, kflag=%u, vlen=%u",
>> @@ -634,6 +645,7 @@ btf_asm_type (ctf_container_ref ctfc, 
>> ctf_dtdef_ref dtd)
>>       case BTF_KIND_UNION:
>>       case BTF_KIND_ENUM:
>>       case BTF_KIND_DATASEC:
>> +    case BTF_KIND_ENUM64:
>>         dw2_asm_output_data (4, dtd->dtd_data.ctti_size, "btt_size: %uB",
>>                  dtd->dtd_data.ctti_size);
>>         return;
>> @@ -707,13 +719,19 @@ btf_asm_sou_member (ctf_container_ref ctfc, 
>> ctf_dmdef_t * dmd)
>>       }
>>   }
>> -/* Asm'out an enum constant following a BTF_KIND_ENUM.  */
>> +/* Asm'out an enum constant following a BTF_KIND_ENUM{,64}.  */
>>   static void
>> -btf_asm_enum_const (ctf_dmdef_t * dmd)
>> +btf_asm_enum_const (unsigned int size, ctf_dmdef_t * dmd)
>>   {
>>     dw2_asm_output_data (4, dmd->dmd_name_offset, "bte_name");
>> -  dw2_asm_output_data (4, dmd->dmd_value, "bte_value");
>> +  if (size == 4)
>> +    dw2_asm_output_data (size, dmd->dmd_value, "bte_value");
>> +  else
>> +    {
>> +      dw2_asm_output_data (4, dmd->dmd_value & 0xffffffff, 
>> "bte_value_lo32");
>> +      dw2_asm_output_data (4, (dmd->dmd_value >> 32) & 0xffffffff, 
>> "bte_value_hi32");
>> +    }
>>   }
>>   /* Asm'out a function parameter description following a 
>> BTF_KIND_FUNC_PROTO.  */
>> @@ -871,7 +889,7 @@ output_asm_btf_sou_fields (ctf_container_ref ctfc, 
>> ctf_dtdef_ref dtd)
>>         btf_asm_sou_member (ctfc, dmd);
>>   }
>> -/* Output all enumerator constants following a BTF_KIND_ENUM.  */
>> +/* Output all enumerator constants following a BTF_KIND_ENUM{,64}.  */
>>   static void
>>   output_asm_btf_enum_list (ctf_container_ref ARG_UNUSED (ctfc),
>> @@ -881,7 +899,7 @@ output_asm_btf_enum_list (ctf_container_ref 
>> ARG_UNUSED (ctfc),
>>     for (dmd = dtd->dtd_u.dtu_members;
>>          dmd != NULL; dmd = (ctf_dmdef_t *) ctf_dmd_list_next (dmd))
>> -    btf_asm_enum_const (dmd);
>> +    btf_asm_enum_const (dtd->dtd_data.ctti_size, dmd);
>>   }
>>   /* Output all function arguments following a BTF_KIND_FUNC_PROTO.  */
>> diff --git a/gcc/ctfc.cc b/gcc/ctfc.cc
>> index 9773358a475..34030cbaa49 100644
>> --- a/gcc/ctfc.cc
>> +++ b/gcc/ctfc.cc
>> @@ -577,7 +577,7 @@ ctf_add_array (ctf_container_ref ctfc, uint32_t 
>> flag, const ctf_arinfo_t * arp,
>>   ctf_id_t
>>   ctf_add_enum (ctf_container_ref ctfc, uint32_t flag, const char * name,
>> -          HOST_WIDE_INT size, dw_die_ref die)
>> +          HOST_WIDE_INT size, bool eunsigned, dw_die_ref die)
>>   {
>>     ctf_dtdef_ref dtd;
>>     ctf_id_t type;
>> @@ -604,6 +604,7 @@ ctf_add_enum (ctf_container_ref ctfc, uint32_t 
>> flag, const char * name,
>>     gcc_assert (size <= CTF_MAX_SIZE);
>>     dtd->dtd_data.ctti_size = size;
>> +  dtd->dtd_enum_unsigned = eunsigned;
>>     ctfc->ctfc_num_stypes++;
>> @@ -630,10 +631,12 @@ ctf_add_enumerator (ctf_container_ref ctfc, 
>> ctf_id_t enid, const char * name,
>>     gcc_assert (kind == CTF_K_ENUM && vlen < CTF_MAX_VLEN);
>> -  /* Enum value is of type HOST_WIDE_INT in the compiler, dmd_value 
>> is int32_t
>> -     on the other hand.  Check bounds and skip adding this enum value 
>> if out of
>> -     bounds.  */
>> -  if ((value > INT_MAX) || (value < INT_MIN))
>> +  /* Enum value is of type HOST_WIDE_INT in the compiler, CTF 
>> enumerators
>> +     values in ctf_enum_t is limited to int32_t, BTF supports signed and
>> +     unsigned enumerators values of 32 and 64 bits, for both debug 
>> formats
>> +     we use ctf_dmdef_t.dmd_value entry of HOST_WIDE_INT type. So check
>> +     CTF bounds and skip adding this enum value if out of bounds.  */
>> +  if (!btf_debuginfo_p() && ((value > INT_MAX) || (value < INT_MIN)))
>>       {
>>         /* FIXME - Note this TBD_CTF_REPRESENTATION_LIMIT.  */
>>         return (1);
>> diff --git a/gcc/ctfc.h b/gcc/ctfc.h
>> index bcf3a43ae1b..48c381a008d 100644
>> --- a/gcc/ctfc.h
>> +++ b/gcc/ctfc.h
>> @@ -133,7 +133,7 @@ typedef struct GTY ((chain_next ("%h.dmd_next"))) 
>> ctf_dmdef
>>     ctf_id_t dmd_type;        /* Type of this member (for sou).  */
>>     uint32_t dmd_name_offset;    /* Offset of the name in str table.  */
>>     uint64_t dmd_offset;        /* Offset of this member in bits (for 
>> sou).  */
>> -  int dmd_value;        /* Value of this member (for enum).  */
>> +  HOST_WIDE_INT dmd_value;    /* Value of this member (for enum).  */
>>     struct ctf_dmdef * dmd_next;    /* A list node.  */
>>   } ctf_dmdef_t;
>> @@ -162,6 +162,7 @@ struct GTY ((for_user)) ctf_dtdef
>>     bool from_global_func; /* Whether this type was added from a global
>>                   function.  */
>>     uint32_t linkage;           /* Used in function types.  0=local, 
>> 1=global.  */
>> +  bool dtd_enum_unsigned;     /* Enum signedness.  */
>>     union GTY ((desc ("ctf_dtu_d_union_selector (&%1)")))
>>     {
>>       /* struct, union, or enum.  */
>> @@ -406,7 +407,7 @@ extern const char * ctf_add_string 
>> (ctf_container_ref, const char *,
>>   extern ctf_id_t ctf_add_reftype (ctf_container_ref, uint32_t, ctf_id_t,
>>                    uint32_t, dw_die_ref);
>>   extern ctf_id_t ctf_add_enum (ctf_container_ref, uint32_t, const 
>> char *,
>> -                  HOST_WIDE_INT, dw_die_ref);
>> +                  HOST_WIDE_INT, bool, dw_die_ref);
>>   extern ctf_id_t ctf_add_slice (ctf_container_ref, uint32_t, ctf_id_t,
>>                      uint32_t, uint32_t, dw_die_ref);
>>   extern ctf_id_t ctf_add_float (ctf_container_ref, uint32_t, const 
>> char *,
>> diff --git a/gcc/dwarf2ctf.cc b/gcc/dwarf2ctf.cc
>> index 397100004c2..748dd0cd8af 100644
>> --- a/gcc/dwarf2ctf.cc
>> +++ b/gcc/dwarf2ctf.cc
>> @@ -736,6 +736,7 @@ gen_ctf_enumeration_type (ctf_container_ref ctfc, 
>> dw_die_ref enumeration)
>>   {
>>     const char *enum_name = get_AT_string (enumeration, DW_AT_name);
>>     unsigned int bit_size = ctf_die_bitsize (enumeration);
>> +  unsigned int signedness = get_AT_unsigned (enumeration, 
>> DW_AT_encoding);
>>     int declaration_p = get_AT_flag (enumeration, DW_AT_declaration);
>>     ctf_id_t enumeration_type_id;
>> @@ -759,7 +760,9 @@ gen_ctf_enumeration_type (ctf_container_ref ctfc, 
>> dw_die_ref enumeration)
>>     /* Generate a CTF type for the enumeration.  */
>>     enumeration_type_id = ctf_add_enum (ctfc, CTF_ADD_ROOT,
>> -                      enum_name, bit_size / 8, enumeration);
>> +                      enum_name, bit_size / 8,
>> +                      (signedness == DW_ATE_unsigned),
>> +                      enumeration);
>>     /* Process the enumerators.  */
>>     {
>> diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-enum-1.c 
>> b/gcc/testsuite/gcc.dg/debug/btf/btf-enum-1.c
>> index 728493b0804..7e940529f1b 100644
>> --- a/gcc/testsuite/gcc.dg/debug/btf/btf-enum-1.c
>> +++ b/gcc/testsuite/gcc.dg/debug/btf/btf-enum-1.c
>> @@ -4,7 +4,7 @@
>>   /* { dg-options "-O0 -gbtf -dA" } */
>>   /* { dg-final { scan-assembler-times "\[\t \]0x6000004\[\t 
>> \]+\[^\n\]*btt_info" 1 } } */
>> -/* { dg-final { scan-assembler-times "\[\t \]0x6000003\[\t 
>> \]+\[^\n\]*btt_info" 1 } } */
>> +/* { dg-final { scan-assembler-times "\[\t \]0x86000003\[\t 
>> \]+\[^\n\]*btt_info" 1 } } */
>>   /* { dg-final { scan-assembler-times "ascii \"QAD.0\"\[\t 
>> \]+\[^\n\]*btf_string" 1 } } */
>>   /* { dg-final { scan-assembler-times "ascii \"QED.0\"\[\t 
>> \]+\[^\n\]*btf_string" 1 } } */
>>   /* { dg-final { scan-assembler-times "ascii \"QOD.0\"\[\t 
>> \]+\[^\n\]*btf_string" 1 } } */
>> diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-enum64-1.c 
>> b/gcc/testsuite/gcc.dg/debug/btf/btf-enum64-1.c
>> new file mode 100644
>> index 00000000000..e443d4c8c00
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/debug/btf/btf-enum64-1.c
>> @@ -0,0 +1,44 @@
>> +/* Test BTF generation for 64 bits enums.  */
>> +
>> +/* { dg-do compile } */
>> +/* { dg-options "-O0 -gbtf -dA" } */
>> +
>> +/* { dg-final { scan-assembler-times "\[\t \].size\[\t \]myenum1,\[\t 
>> \]8" 1 } } */
>> +/* { dg-final { scan-assembler-times "\[\t \].size\[\t \]myenum2,\[\t 
>> \]8" 1 } } */
>> +/* { dg-final { scan-assembler-times "\[\t \].size\[\t \]myenum3,\[\t 
>> \]8" 1 } } */
>> +/* { dg-final { scan-assembler-times "\[\t \]0x13000003\[\t 
>> \]+\[^\n\]*btt_info" 2 } } */
>> +/* { dg-final { scan-assembler-times "\[\t \]0x93000003\[\t 
>> \]+\[^\n\]*btt_info" 1 } } */
>> +/* { dg-final { scan-assembler-times "\[\t \]0xffffffaa\[\t 
>> \]+\[^\n\]*bte_value_lo32" 2 } } */
>> +/* { dg-final { scan-assembler-times "\[\t \]0xff\[\t 
>> \]+\[^\n\]*bte_value_hi32" 3 } } */
>> +/* { dg-final { scan-assembler-times "ascii \"B1.0\"\[\t 
>> \]+\[^\n\]*btf_string" 1 } } */
>> +/* { dg-final { scan-assembler-times "ascii \"B2.0\"\[\t 
>> \]+\[^\n\]*btf_string" 1 } } */
>> +/* { dg-final { scan-assembler-times "ascii \"B3.0\"\[\t 
>> \]+\[^\n\]*btf_string" 1 } } */
>> +/* { dg-final { scan-assembler-times "ascii \"C1.0\"\[\t 
>> \]+\[^\n\]*btf_string" 1 } } */
>> +/* { dg-final { scan-assembler-times "ascii \"C2.0\"\[\t 
>> \]+\[^\n\]*btf_string" 1 } } */
>> +/* { dg-final { scan-assembler-times "ascii \"C3.0\"\[\t 
>> \]+\[^\n\]*btf_string" 1 } } */
>> +/* { dg-final { scan-assembler-times "ascii \"D1.0\"\[\t 
>> \]+\[^\n\]*btf_string" 1 } } */
>> +/* { dg-final { scan-assembler-times "ascii \"D2.0\"\[\t 
>> \]+\[^\n\]*btf_string" 1 } } */
>> +/* { dg-final { scan-assembler-times "ascii \"D3.0\"\[\t 
>> \]+\[^\n\]*btf_string" 1 } } */
>> +/* { dg-final { scan-assembler-times "bte_value_lo32" 9 } } */
>> +/* { dg-final { scan-assembler-times "bte_value_hi32" 9 } } */
>> +
>> +enum default_enum
>> +{
>> +  B1 = 0xffffffffaa,
>> +  B2 = 0xbbbbbbbb,
>> +  B3 = 0xaabbccdd,
>> +} myenum1 = B1;
>> +
>> +enum explicit_unsigned
>> +{
>> +  C1 = 0xffffffffbbUL,
>> +  C2 = 0xbbbbbbbb,
>> +  C3 = 0xaabbccdd,
>> +} myenum2 = C1;
>> +
>> +enum signed64
>> +{
>> +  D1 = 0xffffffffaa,
>> +  D2 = 0xbbbbbbbb,
>> +  D3 = -0x1,
>> +} myenum3 = D1;
>> diff --git a/include/btf.h b/include/btf.h
>> index 78b551ced23..eba67f9d599 100644
>> --- a/include/btf.h
>> +++ b/include/btf.h
>> @@ -109,7 +109,8 @@ struct btf_type
>>   #define BTF_KIND_VAR        14    /* Variable.  */
>>   #define BTF_KIND_DATASEC    15    /* Section such as .bss or .data.  */
>>   #define BTF_KIND_FLOAT        16    /* Floating point.  */
>> -#define BTF_KIND_MAX        BTF_KIND_FLOAT
>> +#define BTF_KIND_ENUM64     19    /* Enumeration up to 64 bits.  */
>> +#define BTF_KIND_MAX        BTF_KIND_ENUM64
>>   #define NR_BTF_KINDS        (BTF_KIND_MAX + 1)
>>   /* For some BTF_KINDs, struct btf_type is immediately followed by
>> @@ -130,14 +131,17 @@ struct btf_type
>>   #define BTF_INT_BOOL    (1 << 2)
>>   /* BTF_KIND_ENUM is followed by VLEN struct btf_enum entries,
>> -   which describe the enumerators. Note that BTF currently only
>> -   supports signed 32-bit enumerator values.  */
>> +   which describe the enumerators. */
>>   struct btf_enum
>>   {
>>     uint32_t name_off;    /* Offset in string section of enumerator 
>> name.  */
>>     int32_t  val;        /* Enumerator value.  */
>>   };
>> +/* BTF_KF_ENUM_ holds the flags for kflags in BTF_KIND_ENUM{,64}.  */
>> +#define BTF_KF_ENUM_UNSIGNED    (0)
>> +#define BTF_KF_ENUM_SIGNED     (1 << 0)
>> +
>>   /* BTF_KIND_ARRAY is followed by a single struct btf_array.  */
>>   struct btf_array
>>   {
>> @@ -190,6 +194,15 @@ struct btf_var_secinfo
>>     uint32_t size;    /* Size (in bytes) of variable.  */
>>   };
>> +/* BTF_KIND_ENUM64 is followed by VLEN struct btf_enum64 entries,
>> +   which describe the 64 bits enumerators.  */
>> +struct btf_enum64
>> +{
>> +  uint32_t name_off;    /* Offset in string section of enumerator 
>> name.  */
>> +  uint32_t val_lo32;    /* lower 32-bit value for a 64-bit value 
>> Enumerator */
>> +  uint32_t val_hi32;    /* high 32-bit value for a 64-bit value 
>> Enumerator */
>> +};
>> +
>>   #ifdef    __cplusplus
>>   }
>>   #endif
>