Re: [PATCH v2 2/2 resend] LoongArch: add model attribute

[Lulu Cheng <chenglulu@loongson.cn>]

在 2022/8/24 下午10:12, Xi Ruoyao 写道:
> On Wed, 2022-08-24 at 22:08 +0800, Xi Ruoyao wrote:
>> v1 -> v2:
>>
>>   * Avoid introduce of SYMBOL_PCREL32, use SYMBOL_PCREL for 32-bit PC
>>     relative.
>>   * Rebase onto a bug fix ([1/2] in the series) to avoid merge conflict.
>>   * Fix missed ChangeLog entries.
> Resend because my mail client has done some stupid thing to the patch :(
>
> -- >8 --
>
> A linker script and/or a section attribute may locate some object
> specially, so we need to handle the code model for such objects
> differently than the -mcmodel setting. This happens when the Linux
> kernel loads a module with per-CPU variables.
>
> Add an attribute to override the code model for a specific variable.
>
> gcc/ChangeLog:
>
> 	* config/loongarch/loongarch-protos.h (loongarch_symbol_type):
> 	Add SYMBOL_PCREL64 and change the description for SYMBOL_PCREL.
> 	* config/loongarch/loongarch.cc (loongarch_attribute_table):
> 	New attribute table.
> 	(TARGET_ATTRIBUTE_TABLE): Define the target hook.
> 	(loongarch_handle_model_attribute): New static function.
> 	(loongarch_classify_symbol): Take TARGET_CMODEL_EXTREME and the
> 	model attribute of SYMBOL_REF_DECL into account returning
> 	SYMBOL_PCREL or SYMBOL_PCREL64.
> 	(loongarch_use_anchors_for_symbol_p): New static function.
> 	(TARGET_USE_ANCHORS_FOR_SYMBOL_P): Define the target hook.
> 	(loongarch_symbol_extreme_p): New static function.
> 	(loongarch_symbolic_constant_p): Handle SYMBOL_PCREL64.
> 	(loongarch_symbol_insns): Likewise.
> 	(loongarch_split_symbol_type): Likewise.
> 	(loongarch_split_symbol): Check SYMBOL_PCREL64 instead of
> 	TARGET_CMODEL_EXTREME for PC-relative addressing.
> 	(loongarch_print_operand_reloc): Likewise.
> 	* doc/extend.texi (Variable Attributes): Document new
> 	LoongArch specific attribute.
>
> gcc/testsuite/ChangeLog:
>
> 	* gcc.target/loongarch/attr-model-test.c: New test.
> 	* gcc.target/loongarch/attr-model-1.c: New test.
> 	* gcc.target/loongarch/attr-model-2.c: New test.
> 	* gcc.target/loongarch/attr-model-diag.c: New test.
> ---
>   gcc/config/loongarch/loongarch-protos.h       |   8 +-
>   gcc/config/loongarch/loongarch.cc             | 190 ++++++++++++++++--
>   gcc/doc/extend.texi                           |  16 ++
>   .../gcc.target/loongarch/attr-model-1.c       |   6 +
>   .../gcc.target/loongarch/attr-model-2.c       |   6 +
>   .../gcc.target/loongarch/attr-model-diag.c    |   7 +
>   .../gcc.target/loongarch/attr-model-test.c    |  25 +++
>   7 files changed, 237 insertions(+), 21 deletions(-)
>   create mode 100644 gcc/testsuite/gcc.target/loongarch/attr-model-1.c
>   create mode 100644 gcc/testsuite/gcc.target/loongarch/attr-model-2.c
>   create mode 100644 gcc/testsuite/gcc.target/loongarch/attr-model-diag.c
>   create mode 100644 gcc/testsuite/gcc.target/loongarch/attr-model-test.c
>
> diff --git a/gcc/config/loongarch/loongarch-protos.h b/gcc/config/loongarch/loongarch-protos.h
> index cadaad7519c..77b2217247d 100644
> --- a/gcc/config/loongarch/loongarch-protos.h
> +++ b/gcc/config/loongarch/loongarch-protos.h
> @@ -28,7 +28,12 @@ along with GCC; see the file COPYING3.  If not see
>          The symbol's value will be loaded directly from the GOT.
>   
>      SYMBOL_PCREL
> -       The symbol's value will be loaded directly from data section.
> +       The symbol's value will be loaded directly from data section within
> +       +/- 2GiB range.
> +
> +   SYMBOL_PCREL64
> +       The symbol's value will be loaded directly from data section within
> +       +/- 8EiB range.
>   
>      SYMBOL_TLS
>          A thread-local symbol.
> @@ -42,6 +47,7 @@ along with GCC; see the file COPYING3.  If not see
>   enum loongarch_symbol_type {
>     SYMBOL_GOT_DISP,
>     SYMBOL_PCREL,
> +  SYMBOL_PCREL64,
>     SYMBOL_TLS,
>     SYMBOL_TLS_IE,
>     SYMBOL_TLS_LE,
> diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc
> index 41d9cca6d31..d9061cdeee3 100644
> --- a/gcc/config/loongarch/loongarch.cc
> +++ b/gcc/config/loongarch/loongarch.cc
> @@ -1633,8 +1633,11 @@ loongarch_rtx_constant_in_small_data_p (machine_mode mode)
>   static enum loongarch_symbol_type
>   loongarch_classify_symbol (const_rtx x)
>   {
> +  enum loongarch_symbol_type pcrel =
> +    TARGET_CMODEL_EXTREME ? SYMBOL_PCREL64 : SYMBOL_PCREL;
> +
>     if (!SYMBOL_REF_P (x))
> -    return SYMBOL_PCREL;
> +    return pcrel;
>   
>     if (SYMBOL_REF_TLS_MODEL (x))
>       return SYMBOL_TLS;
> @@ -1642,7 +1645,28 @@ loongarch_classify_symbol (const_rtx x)
>     if (!loongarch_symbol_binds_local_p (x))
>       return SYMBOL_GOT_DISP;
>   
> -  return SYMBOL_PCREL;
> +  tree t = SYMBOL_REF_DECL (x);
> +  if (!t)
> +    return pcrel;
> +
> +  t = lookup_attribute ("model", DECL_ATTRIBUTES (t));
> +  if (!t)
> +    return pcrel;
> +
> +  t = TREE_VALUE (TREE_VALUE (t));
> +
> +  /* loongarch_handle_model_attribute should reject other values.  */
> +  gcc_assert (TREE_CODE (t) == STRING_CST);
> +
> +  const char *model = TREE_STRING_POINTER (t);
> +  if (strcmp (model, "normal") == 0)
> +    return SYMBOL_PCREL;
> +  if (strcmp (model, "extreme") == 0)
> +    return SYMBOL_PCREL64;
> +
> +  /* loongarch_handle_model_attribute should reject unknown model
> +     name.  */
> +  gcc_unreachable ();
>   }
>   
>   /* Classify the base of symbolic expression X, given that X appears in
> @@ -1695,6 +1719,7 @@ loongarch_symbolic_constant_p (rtx x, enum loongarch_symbol_type *symbol_type)
>       case SYMBOL_TLSGD:
>       case SYMBOL_TLSLDM:
>       case SYMBOL_PCREL:
> +    case SYMBOL_PCREL64:
>         /* GAS rejects offsets outside the range [-2^31, 2^31-1].  */
>         return sext_hwi (INTVAL (offset), 32) == INTVAL (offset);
>   
> @@ -1729,6 +1754,9 @@ loongarch_symbol_insns (enum loongarch_symbol_type type, machine_mode mode)
>       case SYMBOL_TLSLDM:
>         return 3;
>   
> +    case SYMBOL_PCREL64:
> +      return 5;
> +
>       case SYMBOL_TLS:
>         /* We don't treat a bare TLS symbol as a constant.  */
>         return 0;
> @@ -1833,7 +1861,7 @@ loongarch_valid_offset_p (rtx x, machine_mode mode)
>     return true;
>   }
>   
> -/* Should a symbol of type SYMBOL_TYPE should be split in two?  */
> +/* Should a symbol of type SYMBOL_TYPE should be split in two or more?  */
>   
>   bool
>   loongarch_split_symbol_type (enum loongarch_symbol_type symbol_type)
> @@ -1841,6 +1869,7 @@ loongarch_split_symbol_type (enum loongarch_symbol_type symbol_type)
>     switch (symbol_type)
>       {
>       case SYMBOL_PCREL:
> +    case SYMBOL_PCREL64:
>       case SYMBOL_GOT_DISP:
>       case SYMBOL_TLS_IE:
>       case SYMBOL_TLS_LE:
> @@ -2718,6 +2747,20 @@ loongarch_force_address (rtx x, machine_mode mode)
>     return x;
>   }
>   
> +static bool
> +loongarch_symbol_extreme_p (enum loongarch_symbol_type type)
> +{
> +  switch (type)
> +    {
> +      case SYMBOL_PCREL:
> +	return false;
> +      case SYMBOL_PCREL64:
> +	return true;
> +      default:
> +	return TARGET_CMODEL_EXTREME;
> +    }
> +}
> +
>   /* If MODE is MAX_MACHINE_MODE, ADDR appears as a move operand, otherwise
>      it appears in a MEM of that mode.  Return true if ADDR is a legitimate
>      constant in that context and can be split into high and low parts.
> @@ -2757,7 +2800,7 @@ loongarch_split_symbol (rtx temp, rtx addr, machine_mode mode, rtx *low_out)
>     high = gen_rtx_HIGH (Pmode, copy_rtx (addr));
>     high = loongarch_force_temporary (temp, high);
>   
> -  if (TARGET_CMODEL_EXTREME && can_create_pseudo_p ())
> +  if (loongarch_symbol_extreme_p (symbol_type) && can_create_pseudo_p ())
>       {
>         gcc_assert (TARGET_EXPLICIT_RELOCS);
>   
> @@ -2771,14 +2814,16 @@ loongarch_split_symbol (rtx temp, rtx addr, machine_mode mode, rtx *low_out)
>     if (low_out)
>       switch (symbol_type)
>         {
> -      case SYMBOL_PCREL:
> -	{
> -	  if (TARGET_CMODEL_EXTREME && can_create_pseudo_p ())
> +      case SYMBOL_PCREL64:
> +	if (can_create_pseudo_p ())
> +	  {
>   	    *low_out = gen_rtx_PLUS (Pmode, high, temp1);
> -	  else
> -	    *low_out = gen_rtx_LO_SUM (Pmode, high, addr);
> -	  break;
> -	}
> +	    break;
> +	  }
> +	/* fall through */
> +      case SYMBOL_PCREL:
> +	*low_out = gen_rtx_LO_SUM (Pmode, high, addr);
> +	break;
>   
>         case SYMBOL_GOT_DISP:
>   	/* SYMBOL_GOT_DISP symbols are loaded from the GOT.  */
> @@ -4745,22 +4790,23 @@ loongarch_print_operand_reloc (FILE *file, rtx op, bool hi64_part,
>   			       bool hi_reloc)
>   {
>     const char *reloc;
> +  enum loongarch_symbol_type symbol_type =
> +    loongarch_classify_symbolic_expression (op);
>   
> -  if (TARGET_CMODEL_EXTREME)
> +  if (loongarch_symbol_extreme_p (symbol_type))
>       gcc_assert (TARGET_EXPLICIT_RELOCS);
>   
> -  switch (loongarch_classify_symbolic_expression (op))
> +  switch (symbol_type)
>       {
> -    case SYMBOL_PCREL:
> +    case SYMBOL_PCREL64:
>         if (hi64_part)
>   	{
> -	  if (TARGET_CMODEL_EXTREME)
> -	    reloc = hi_reloc ? "%pc64_hi12" : "%pc64_lo20";
> -	  else
> -	    gcc_unreachable ();
> +	  reloc = hi_reloc ? "%pc64_hi12" : "%pc64_lo20";
> +	  break;
>   	}
> -      else
> -	reloc = hi_reloc ? "%pc_hi20" : "%pc_lo12";
> +      /* fall through */
> +    case SYMBOL_PCREL:
> +      reloc = hi_reloc ? "%pc_hi20" : "%pc_lo12";
>         break;
>   
>       case SYMBOL_GOT_DISP:
> @@ -6316,6 +6362,104 @@ loongarch_starting_frame_offset (void)
>     return crtl->outgoing_args_size;
>   }
>   
> +static tree
> +loongarch_handle_model_attribute (tree *node, tree name, tree arg, int,
> +				  bool *no_add_attrs)
> +{
> +  tree decl = *node;
> +  if (TREE_CODE (decl) == VAR_DECL)
> +    {
> +      if (DECL_THREAD_LOCAL_P (decl))
> +	{
> +	  error_at (DECL_SOURCE_LOCATION (decl),
> +		    "%qE attribute cannot be specified for thread-local "
> +		    "variables", name);
> +	  *no_add_attrs = true;
> +	  return NULL_TREE;
> +	}
> +      if (DECL_CONTEXT (decl)
> +	  && TREE_CODE (DECL_CONTEXT (decl)) == FUNCTION_DECL
> +	  && !TREE_STATIC (decl))
> +	{
> +	  error_at (DECL_SOURCE_LOCATION (decl),
> +		    "%qE attribute cannot be specified for local "
> +		    "variables", name);
> +	  *no_add_attrs = true;
> +	  return NULL_TREE;
> +	}
> +      if (DECL_REGISTER (decl))
> +	{
> +	  error_at (DECL_SOURCE_LOCATION (decl),
> +		    "%qE attribute cannot be specified for register "
> +		    "variables", name);
> +	  *no_add_attrs = true;
> +	  return NULL_TREE;
> +	}
> +      if (!TARGET_EXPLICIT_RELOCS)
> +	{
> +	  error_at (DECL_SOURCE_LOCATION (decl),
> +		    "%qE attribute requires %s", name, "-mexplicit-relocs");
> +	  *no_add_attrs = true;
> +	  return NULL_TREE;
> +	}
> +
> +      arg = TREE_VALUE (arg);
> +      if (TREE_CODE (arg) != STRING_CST)
> +	{
> +	  error_at (DECL_SOURCE_LOCATION (decl),
> +		    "invalid argument of %qE attribute", name);
> +	  *no_add_attrs = true;
> +	  return NULL_TREE;
> +	}
> +
> +      const char *model = TREE_STRING_POINTER (arg);
> +      if (strcmp (model, "normal") != 0
> +	  && strcmp (model, "extreme") != 0)
> +	{
> +	  error_at (DECL_SOURCE_LOCATION (decl),
> +		    "invalid argument of %qE attribute", name);
> +	  *no_add_attrs = true;
> +	  return NULL_TREE;
> +	}
> +
> +      if (lookup_attribute ("model", DECL_ATTRIBUTES (decl)))
> +	{
> +	  error_at (DECL_SOURCE_LOCATION (decl),
> +		    "multiple %qE attribute", name);
> +	  *no_add_attrs = true;
> +	  return NULL_TREE;
> +	}
> +    }
> +  else
> +    {
> +      warning (OPT_Wattributes, "%qE attribute ignored", name);
> +      *no_add_attrs = true;
> +    }
> +  return NULL_TREE;
> +}
> +
> +static const struct attribute_spec loongarch_attribute_table[] =
> +{
> +  /* { name, min_len, max_len, decl_req, type_req, fn_type_req,
> +       affects_type_identity, handler, exclude } */
> +  { "model", 1, 1, true, false, false, false,
> +    loongarch_handle_model_attribute, NULL },
> +  /* The last attribute spec is set to be NULL.  */
> +  {}
> +};
> +
> +bool
> +loongarch_use_anchors_for_symbol_p (const_rtx symbol)
> +{
> +  tree decl = SYMBOL_REF_DECL (symbol);
> +
> +  /* The section anchor optimization may break custom address model.  */
> +  if (decl && lookup_attribute ("model", DECL_ATTRIBUTES (decl)))
> +    return false;
> +
> +  return default_use_anchors_for_symbol_p (symbol);
> +}
> +
>   /* Initialize the GCC target structure.  */
>   #undef TARGET_ASM_ALIGNED_HI_OP
>   #define TARGET_ASM_ALIGNED_HI_OP "\t.half\t"
> @@ -6504,6 +6648,12 @@ loongarch_starting_frame_offset (void)
>   #undef  TARGET_HAVE_SPECULATION_SAFE_VALUE
>   #define TARGET_HAVE_SPECULATION_SAFE_VALUE speculation_safe_value_not_needed
>   
> +#undef  TARGET_ATTRIBUTE_TABLE
> +#define TARGET_ATTRIBUTE_TABLE loongarch_attribute_table
> +
> +#undef  TARGET_USE_ANCHORS_FOR_SYMBOL_P
> +#define TARGET_USE_ANCHORS_FOR_SYMBOL_P loongarch_use_anchors_for_symbol_p
> +
>   struct gcc_target targetm = TARGET_INITIALIZER;
>   
>   #include "gt-loongarch.h"
> diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
> index 7fe7f8817cd..431811c7b26 100644
> --- a/gcc/doc/extend.texi
> +++ b/gcc/doc/extend.texi
> @@ -7314,6 +7314,7 @@ attributes.
>   * Blackfin Variable Attributes::
>   * H8/300 Variable Attributes::
>   * IA-64 Variable Attributes::
> +* LoongArch Variable Attributes::
>   * M32R/D Variable Attributes::
>   * MeP Variable Attributes::
>   * Microsoft Windows Variable Attributes::
> @@ -8098,6 +8099,21 @@ defined by shared libraries.
>   
>   @end table
>   
> +@node LoongArch Variable Attributes
> +@subsection LoongArch Variable Attributes
> +
> +One attribute is currently defined for the LoongArch.
> +
> +@table @code
> +@item model("@var{name}")
> +@cindex @code{model} variable attribute, LoongArch
> +Use this attribute on the LoongArch to use a different code model for
> +addressing this variable, than the code model specified by the global
> +@option{-mcmodel} option.This attribute is mostly useful if a
> +@code{section} attribute and/or a linker script will locate this object
> +specially.

I think this should add a sentence:

"Currently, the identifier name can only be one of small or extreme." 
Others I think are ok.

> +@end table
> +
>   @node M32R/D Variable Attributes
>   @subsection M32R/D Variable Attributes
>   
> diff --git a/gcc/testsuite/gcc.target/loongarch/attr-model-1.c b/gcc/testsuite/gcc.target/loongarch/attr-model-1.c
> new file mode 100644
> index 00000000000..916d715b98b
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/loongarch/attr-model-1.c
> @@ -0,0 +1,6 @@
> +/* { dg-do compile } */
> +/* { dg-options "-mexplicit-relocs -mcmodel=normal -O2" } */
> +/* { dg-final { scan-assembler-times "%pc64_hi12" 2 } } */
> +
> +#define ATTR_MODEL_TEST
> +#include "attr-model-test.c"
> diff --git a/gcc/testsuite/gcc.target/loongarch/attr-model-2.c b/gcc/testsuite/gcc.target/loongarch/attr-model-2.c
> new file mode 100644
> index 00000000000..a74c795ac3e
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/loongarch/attr-model-2.c
> @@ -0,0 +1,6 @@
> +/* { dg-do compile } */
> +/* { dg-options "-mexplicit-relocs -mcmodel=extreme -O2" } */
> +/* { dg-final { scan-assembler-times "%pc64_hi12" 3 } } */
> +
> +#define ATTR_MODEL_TEST
> +#include "attr-model-test.c"
> diff --git a/gcc/testsuite/gcc.target/loongarch/attr-model-diag.c b/gcc/testsuite/gcc.target/loongarch/attr-model-diag.c
> new file mode 100644
> index 00000000000..88beede74df
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/loongarch/attr-model-diag.c
> @@ -0,0 +1,7 @@
> +/* { dg-do compile } */
> +/* { dg-options "-mexplicit-relocs" } */
> +
> +__thread int x __attribute__((model("extreme"))); /* { dg-error "attribute cannot be specified for thread-local variables" } */
> +register int y __asm__("tp") __attribute__((model("extreme"))); /* { dg-error "attribute cannot be specified for register variables" } */
> +int z __attribute__((model(114))); /* { dg-error "invalid argument" } */
> +int t __attribute__((model("good"))); /* { dg-error "invalid argument" } */
> diff --git a/gcc/testsuite/gcc.target/loongarch/attr-model-test.c b/gcc/testsuite/gcc.target/loongarch/attr-model-test.c
> new file mode 100644
> index 00000000000..5b61a7af9c3
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/loongarch/attr-model-test.c
> @@ -0,0 +1,25 @@
> +#ifdef ATTR_MODEL_TEST
> +int x __attribute__((model("extreme")));
> +int y __attribute__((model("normal")));
> +int z;
> +
> +int
> +test(void)
> +{
> +  return x + y + z;
> +}
> +
> +/* The following will be used for kernel per-cpu storage implemention. */
> +
> +register char *per_cpu_base __asm__("r21");
> +static int counter __attribute__((section(".data..percpu"), model("extreme")));
> +
> +void
> +inc_counter(void)
> +{
> +  int *ptr = (int *)(per_cpu_base + (long)&counter);
> +  (*ptr)++;
> +}
> +#endif
> +
> +int dummy;