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From: Xi Ruoyao <xry111@xry111.site>
To: gcc-patches@gcc.gnu.org, Lulu Cheng <chenglulu@loongson.cn>
Cc: Chenghua Xu <xuchenghua@loongson.cn>,
	Youling Tang <tangyouling@loongson.cn>,
	 Huacai Chen <chenhuacai@kernel.org>,
	Jinyang He <hejinyang@loongson.cn>, Wang Xuerui <i@xen0n.name>
Subject: LoongArch: add model attribute
Date: Tue, 23 Aug 2022 22:51:45 +0800	[thread overview]
Message-ID: <fc317f3943c4ea7810ccf532707c6a3255ecd3a0.camel@xry111.site> (raw)

Another attempt to make kernel module happy.

One remaining issue: the patch cannot diagnostic some insane thing like

    int x __attribute__((model("normal")));
    int x __attribute__((model("extreme")));

It seems incredibly difficult to diagnose such thing: I can't figure out
any solution w/o invasion into the frontend.  IA-64 model() only accepts
small so this is not a problem for them, and M32R model() also cannot
diagnose such error.

Any suggestion is welcomed.

-- >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_PCREL32 and SYMBOL_PCREL64.
	* 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): Return SYMBOL_PCREL{32,64} for
	SYMBOL_REF_DECL with model attribute.
	(loongarch_use_anchors_for_symbol_p): New static function.
	(TARGET_USE_ANCHORS_FOR_SYMBOL_P): Define the target hook.
	* 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             | 175 +++++++++++++++++-
 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, 236 insertions(+), 7 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..4e925aa3876 100644
--- a/gcc/config/loongarch/loongarch-protos.h
+++ b/gcc/config/loongarch/loongarch-protos.h
@@ -30,6 +30,12 @@ along with GCC; see the file COPYING3.  If not see
    SYMBOL_PCREL
        The symbol's value will be loaded directly from data section.
 
+   SYMBOL_PCREL32
+   SYMBOL_PCREL64
+       Like SYMBOL_PCREL, but the PC-relative offset of the symbol is
+       assumed to be in the +/- 2GiB or +/- 8 EiB range, instead of the
+       code model specification.
+
    SYMBOL_TLS
        A thread-local symbol.
 
@@ -42,6 +48,8 @@ along with GCC; see the file COPYING3.  If not see
 enum loongarch_symbol_type {
   SYMBOL_GOT_DISP,
   SYMBOL_PCREL,
+  SYMBOL_PCREL32,
+  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 207ac2762c6..3917c53dd27 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -1643,6 +1643,32 @@ loongarch_classify_symbol (const_rtx x)
       && !loongarch_symbol_binds_local_p (x))
     return SYMBOL_GOT_DISP;
 
+  if (SYMBOL_REF_P (x))
+    {
+      tree t = SYMBOL_REF_DECL (x);
+      if (!t)
+	return SYMBOL_PCREL;
+
+      t = lookup_attribute ("model", DECL_ATTRIBUTES (t));
+      if (!t)
+	return SYMBOL_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_PCREL32;
+      if (strcmp (model, "extreme") == 0)
+	return SYMBOL_PCREL64;
+
+      /* loongarch_handle_model_attribute should reject unknown model
+	 name.  */
+      gcc_unreachable ();
+    }
+
   return SYMBOL_PCREL;
 }
 
@@ -1696,6 +1722,8 @@ loongarch_symbolic_constant_p (rtx x, enum loongarch_symbol_type *symbol_type)
     case SYMBOL_TLSGD:
     case SYMBOL_TLSLDM:
     case SYMBOL_PCREL:
+    case SYMBOL_PCREL32:
+    case SYMBOL_PCREL64:
       /* GAS rejects offsets outside the range [-2^31, 2^31-1].  */
       return sext_hwi (INTVAL (offset), 32) == INTVAL (offset);
 
@@ -1721,7 +1749,7 @@ loongarch_symbol_insns (enum loongarch_symbol_type type, machine_mode mode)
 
       return 3;
 
-    case SYMBOL_PCREL:
+    case SYMBOL_PCREL32:
     case SYMBOL_TLS_IE:
     case SYMBOL_TLS_LE:
       return 2;
@@ -1730,6 +1758,12 @@ loongarch_symbol_insns (enum loongarch_symbol_type type, machine_mode mode)
     case SYMBOL_TLSLDM:
       return 3;
 
+    case SYMBOL_PCREL64:
+      return 5;
+
+    case SYMBOL_PCREL:
+      return TARGET_CMODEL_EXTREME ? 5 : 2;
+
     case SYMBOL_TLS:
       /* We don't treat a bare TLS symbol as a constant.  */
       return 0;
@@ -1834,7 +1868,7 @@ 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)
@@ -1842,6 +1876,8 @@ loongarch_split_symbol_type (enum loongarch_symbol_type symbol_type)
   switch (symbol_type)
     {
     case SYMBOL_PCREL:
+    case SYMBOL_PCREL32:
+    case SYMBOL_PCREL64:
     case SYMBOL_GOT_DISP:
     case SYMBOL_TLS_IE:
     case SYMBOL_TLS_LE:
@@ -2649,6 +2685,22 @@ 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_PCREL32:
+	*type = SYMBOL_PCREL;
+	return false;
+      case SYMBOL_PCREL64:
+	*type = SYMBOL_PCREL;
+	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.
@@ -2688,7 +2740,9 @@ 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 ())
+  bool extreme = loongarch_symbol_extreme_p (&symbol_type);
+
+  if (extreme && can_create_pseudo_p ())
     {
       gcc_assert (TARGET_EXPLICIT_RELOCS);
 
@@ -2704,7 +2758,7 @@ loongarch_split_symbol (rtx temp, rtx addr, machine_mode mode, rtx *low_out)
       {
       case SYMBOL_PCREL:
 	{
-	  if (TARGET_CMODEL_EXTREME && can_create_pseudo_p ())
+	  if (extreme && can_create_pseudo_p ())
 	    *low_out = gen_rtx_PLUS (Pmode, high, temp1);
 	  else
 	    *low_out = gen_rtx_LO_SUM (Pmode, high, addr);
@@ -4676,16 +4730,19 @@ 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);
+  bool extreme = loongarch_symbol_extreme_p (&symbol_type);
 
-  if (TARGET_CMODEL_EXTREME)
+  if (extreme)
     gcc_assert (TARGET_EXPLICIT_RELOCS);
 
-  switch (loongarch_classify_symbolic_expression (op))
+  switch (symbol_type)
     {
     case SYMBOL_PCREL:
       if (hi64_part)
 	{
-	  if (TARGET_CMODEL_EXTREME)
+	  if (extreme)
 	    reloc = hi_reloc ? "%pc64_hi12" : "%pc64_lo20";
 	  else
 	    gcc_unreachable ();
@@ -6246,6 +6303,104 @@ 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"
@@ -6434,6 +6589,12 @@ 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.
+@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;
-- 
2.37.2



             reply	other threads:[~2022-08-23 14:52 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-23 14:51 Xi Ruoyao [this message]
2022-08-24  6:54 ` Lulu Cheng
2022-08-24  6:54   ` Lulu Cheng
2022-08-30 13:42 ` Richard Sandiford

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