[gcc r14-5682] Add register filter operand to define_register_constraint

[gcc r14-5682] Add register filter operand to define_register_constraint

[Richard Sandiford]

https://gcc.gnu.org/g:09a85191d01e337d84f9c4bc13f3515e8b40e3af

commit r14-5682-g09a85191d01e337d84f9c4bc13f3515e8b40e3af
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Tue Nov 21 15:39:09 2023 +0000

    Add register filter operand to define_register_constraint
    
    The main way of enforcing registers to be aligned is through
    HARD_REGNO_MODE_OK.  But this is a global property that applies
    to all operands.  A given (regno, mode) pair is either globally
    valid or globally invalid.
    
    This patch instead adds a way of specifying that individual operands
    must be aligned.  More generally, it allows constraints to specify
    a C++ condition that the operand's REGNO must satisfy.  The condition
    must be invariant for a given set of target options, so that it can
    be precomputed and cached as a HARD_REG_SET.
    
    This information will be used in very compile-time-sensitive
    parts of the compiler.  A lot of the complication is in allowing
    the information to be stored and tested without much memory cost,
    and without impacting targets that don't use the feature.
    
    Specifically:
    
    - Constraints are encouraged to test the absolute REGNO rather than
      an offset from the start of the containing class.  For example,
      all constraints for even registers should use the same condition,
      such as "regno % 2 == 0".  This requires the classes to start at
      even register boundaries, but that's already an implicit
      requirement due to things like the ira-costs.cc code that begins:
    
          /* Some targets allow pseudos to be allocated to unaligned sequences
             of hard registers.  However, selecting an unaligned sequence can
             unnecessarily restrict later allocations.  So increase the cost of
             unaligned hard regs to encourage the use of aligned hard regs.  */
    
    - Each unique condition is given a "filter identifier".
    
    - The total number of filters is given by NUM_REGISTER_FILTERS,
      defined automatically in insn-config.h.  Structures can therefore use
      a bitfield of NUM_REGISTER_FILTERS to represent a mask of filters.
    
    - There is a new target global, target_constraints, that caches the
      HARD_REG_SET for each filter.
    
    - There is a function for looking up the HARD_REG_SET filter for a given
      constraint and one for looking up the filter id.  Both simply return
      a constant on targets that don't use the feature.
    
    - There are functions for testing a register against a specific filter,
      or against a mask of filters.
    
    This patch just adds the information.  Later ones make use of it.
    
    gcc/
            * rtl.def (DEFINE_REGISTER_CONSTRAINT): Add an optional filter
            operand.
            * doc/md.texi (define_register_constraint): Document it.
            * doc/tm.texi.in: Reference it in discussion about aligned registers.
            * doc/tm.texi: Regenerate.
            * gensupport.h (register_filters, get_register_filter_id): Declare.
            * gensupport.cc (register_filter_map, register_filters): New variables.
            (get_register_filter_id): New function.
            (process_define_register_constraint): Likewise.
            (process_rtx): Pass define_register_constraints to
            process_define_register_constraint.
            * genconfig.cc (main): Emit a definition of NUM_REGISTER_FILTERS.
            * genpreds.cc (constraint_data): Add a filter field.
            (add_constraint): Update accordingly.
            (process_define_register_constraint): Pass the filter operand.
            (write_init_reg_class_start_regs): New function.
            (write_get_register_filter): Likewise.
            (write_get_register_filter_id): Likewise.
            (write_tm_preds_h): Write a definition of target_constraints,
            plus helpers to test its contents.  Write the get_register_filter*
            functions.
            (write_insn_preds_c): Write init_reg_class_start_regs.
            * reginfo.cc (init_reg_class_start_regs): Declare.
            (init_reg_sets): Call it.
            * target-globals.h (this_target_constraints): Declare.
            (target_globals): Add a constraints field.
            (restore_target_globals): Update accordingly.
            * target-globals.cc: Include tm_p.h.
            (default_target_globals): Initialize the constraints field.
            (save_target_globals): Handle the constraints field.
            (target_globals::~target_globals): Likewise.

Diff:
---
 gcc/doc/md.texi       |  41 +++++++++++++-
 gcc/doc/tm.texi       |   3 +-
 gcc/doc/tm.texi.in    |   3 +-
 gcc/genconfig.cc      |   2 +
 gcc/genpreds.cc       | 146 ++++++++++++++++++++++++++++++++++++++++++++++++--
 gcc/gensupport.cc     |  48 ++++++++++++++++-
 gcc/gensupport.h      |   3 ++
 gcc/reginfo.cc        |   5 ++
 gcc/rtl.def           |   6 ++-
 gcc/target-globals.cc |   6 ++-
 gcc/target-globals.h  |   3 ++
 11 files changed, 254 insertions(+), 12 deletions(-)

diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
index e01cdcbe22c..df6725ffc9c 100644
--- a/gcc/doc/md.texi
+++ b/gcc/doc/md.texi
@@ -4516,8 +4516,8 @@ Register constraints correspond directly to register classes.
 @xref{Register Classes}.  There is thus not much flexibility in their
 definitions.
 
-@deffn {MD Expression} define_register_constraint name regclass docstring
-All three arguments are string constants.
+@deffn {MD Expression} define_register_constraint name regclass docstring [filter]
+All arguments are string constants.
 @var{name} is the name of the constraint, as it will appear in
 @code{match_operand} expressions.  If @var{name} is a multi-letter
 constraint its length shall be the same for all constraints starting
@@ -4529,6 +4529,43 @@ look at the operand.  The usual use of expressions is to map some
 register constraints to @code{NO_REGS} when the register class
 is not available on a given subarchitecture.
 
+If an operand occupies multiple hard registers, the constraint
+requires all of those registers to belong to @var{regclass}.
+For example, if @var{regclass} is @code{GENERAL_REGS} and
+@code{GENERAL_REGS} contains registers @code{r0} to @code{r15},
+the constraint does not allow @var{r15} to be used for modes
+that occupy more than one register.
+
+@cindex @code{TARGET_HARD_REGNO_MODE_OK} and constraints
+The choice of register is also constrained by @code{TARGET_HARD_REGNO_MODE_OK}.
+For example, if @code{TARGET_HARD_REGNO_MODE_OK} disallows @samp{(reg:DI r1)},
+that requirement applies to all constraints whose classes include @code{r1}.
+
+However, it is sometimes useful to impose extra operand-specific
+requirements on the register number.  For example, a target might not
+want to prevent @emph{all} odd-even pairs from holding @code{DImode}
+values, but it might still need to prevent specific operands from
+having an odd-numbered register.  The optional @var{filter} argument
+exists for such cases.  When given, @var{filter} is a C++ expression
+that evaluates to true if @code{regno} is a valid register for the
+operand.  If an operand occupies multiple registers, the condition
+applies only to the first register.
+
+For example:
+
+@smallexample
+(define_register_constraint "e" "GENERAL_REGS" "..." "regno % 2 == 0")
+@end smallexample
+
+defines a constraint that requires an even-numbered general register.
+
+Filter conditions that impose an alignment are encouraged to test
+the alignment of @code{regno} itself, as in the example, rather than
+calculate an offset relative to the start of the class.  If it is
+sometimes necessary for a register of class @var{c} to be aligned
+to @var{n}, the first register in @var{c} should itself by divisible
+by @var{n}.
+
 @var{docstring} is a sentence documenting the meaning of the
 constraint.  Docstrings are explained further below.
 @end deffn
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index dcf77359e66..645559ea084 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -2478,7 +2478,8 @@ When a value occupying several consecutive registers is expected in a
 certain class, all the registers used must belong to that class.
 Therefore, register classes cannot be used to enforce a requirement for
 a register pair to start with an even-numbered register.  The way to
-specify this requirement is with @code{TARGET_HARD_REGNO_MODE_OK}.
+specify this requirement is with @code{TARGET_HARD_REGNO_MODE_OK},
+or with a filter expression in a @code{define_register_constraint}.
 
 Register classes used for input-operands of bitwise-and or shift
 instructions have a special requirement: each such class must have, for
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index b61a59fdaf3..4ddc8507ed9 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -2060,7 +2060,8 @@ When a value occupying several consecutive registers is expected in a
 certain class, all the registers used must belong to that class.
 Therefore, register classes cannot be used to enforce a requirement for
 a register pair to start with an even-numbered register.  The way to
-specify this requirement is with @code{TARGET_HARD_REGNO_MODE_OK}.
+specify this requirement is with @code{TARGET_HARD_REGNO_MODE_OK},
+or with a filter expression in a @code{define_register_constraint}.
 
 Register classes used for input-operands of bitwise-and or shift
 instructions have a special requirement: each such class must have, for
diff --git a/gcc/genconfig.cc b/gcc/genconfig.cc
index 2ee323f80c3..c8c2ebef21c 100644
--- a/gcc/genconfig.cc
+++ b/gcc/genconfig.cc
@@ -360,6 +360,8 @@ main (int argc, const char **argv)
       printf ("#define MAX_INSNS_PER_PEEP2 0\n");
     }
 
+  printf ("#define NUM_REGISTER_FILTERS %d\n", register_filters.length ());
+
   puts ("\n#endif /* GCC_INSN_CONFIG_H */");
 
   if (ferror (stdout) || fflush (stdout) || fclose (stdout))
diff --git a/gcc/genpreds.cc b/gcc/genpreds.cc
index bdd65ef7d7a..5535a7512fb 100644
--- a/gcc/genpreds.cc
+++ b/gcc/genpreds.cc
@@ -677,6 +677,7 @@ public:
   size_t namelen;
   const char *regclass;  /* for register constraints */
   rtx exp;               /* for other constraints */
+  const char *filter;    /* the register filter condition, or null if none */
   unsigned int is_register	: 1;
   unsigned int is_const_int	: 1;
   unsigned int is_const_dbl	: 1;
@@ -763,7 +764,8 @@ mangle (const char *name)
    is the register class, if any; EXP is the expression to test, if any;
    IS_MEMORY, IS_SPECIAL_MEMORY, IS_RELAXED_MEMORY and IS_ADDRESS indicate
    memory, special memory, and address constraints, respectively; LOC is the .md
-   file location.
+   file location; FILTER is the filter condition for a register constraint,
+   or null if none.
 
    Not all combinations of arguments are valid; most importantly, REGCLASS is
    mutually exclusive with EXP, and
@@ -776,7 +778,8 @@ mangle (const char *name)
 static void
 add_constraint (const char *name, const char *regclass,
 		rtx exp, bool is_memory, bool is_special_memory,
-		bool is_relaxed_memory, bool is_address, file_location loc)
+		bool is_relaxed_memory, bool is_address, file_location loc,
+		const char *filter = nullptr)
 {
   class constraint_data *c, **iter, **slot;
   const char *p;
@@ -908,6 +911,7 @@ add_constraint (const char *name, const char *regclass,
   c->namelen = namelen;
   c->regclass = regclass;
   c->exp = exp;
+  c->filter = filter;
   c->is_register = regclass != 0;
   c->is_const_int = is_const_int;
   c->is_const_dbl = is_const_dbl;
@@ -966,7 +970,8 @@ static void
 process_define_register_constraint (md_rtx_info *info)
 {
   add_constraint (XSTR (info->def, 0), XSTR (info->def, 1),
-		  0, false, false, false, false, info->loc);
+		  0, false, false, false, false, info->loc,
+		  XSTR (info->def, 3));
 }
 
 /* Put the constraints into enum order.  We want to keep constraints
@@ -1319,6 +1324,34 @@ write_insn_const_int_ok_for_constraint (void)
 	"  return false;\n"
 	"}\n");
 }
+
+/* Print the init_reg_class_start_regs function, which initializes
+   this_target_constraints->register_filters from the C conditions
+   in the define_register_constraints.  */
+static void
+write_init_reg_class_start_regs ()
+{
+  printf ("\n"
+	  "void\n"
+	  "init_reg_class_start_regs ()\n"
+	  "{\n");
+  if (!register_filters.is_empty ())
+    {
+      printf ("  for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER;"
+	      " ++regno)\n"
+	      "    {\n");
+      for (unsigned int i = 0; i < register_filters.length (); ++i)
+	{
+	  printf ("      if (");
+	  rtx_reader_ptr->print_c_condition (register_filters[i]);
+	  printf (")\n"
+		  "        SET_HARD_REG_BIT (%s[%d], regno);\n",
+		  "this_target_constraints->register_filters", i);
+	}
+      printf ("    }\n");
+    }
+  printf ("}\n");
+}
 \f
 /* Write a definition for a function NAME that returns true if a given
    constraint_num is in the range [START, END).  */
@@ -1401,6 +1434,54 @@ print_type_tree (const vec <std::pair <unsigned int, const char *> > &vec,
   printf ("%*sreturn %s;\n", indent, "", fallback);
 }
 
+/* Print the get_register_filter function, which returns a pointer
+   to the start register filter for a given constraint, or null if none.  */
+static void
+write_get_register_filter ()
+{
+  constraint_data *c;
+
+  printf ("\n"
+	  "#ifdef GCC_HARD_REG_SET_H\n"
+	  "static inline const HARD_REG_SET *\n"
+	  "get_register_filter (constraint_num%s)\n",
+	  register_filters.is_empty () ? "" : " c");
+  printf ("{\n");
+  FOR_ALL_CONSTRAINTS (c)
+    if (c->is_register && c->filter)
+      {
+	printf ("  if (c == CONSTRAINT_%s)\n", c->c_name);
+	printf ("    return &this_target_constraints->register_filters[%d];\n",
+		get_register_filter_id (c->filter));
+      }
+  printf ("  return nullptr;\n"
+	  "}\n"
+	  "#endif\n");
+}
+
+/* Print the get_register_filter_id function, which returns the index
+   of the given constraint's register filter in
+   this_target_constraints->register_filters, or -1 if none.  */
+static void
+write_get_register_filter_id ()
+{
+  constraint_data *c;
+
+  printf ("\n"
+	  "static inline int\n"
+	  "get_register_filter_id (constraint_num%s)\n",
+	  register_filters.is_empty () ? "" : " c");
+  printf ("{\n");
+  FOR_ALL_CONSTRAINTS (c)
+    if (c->is_register && c->filter)
+      {
+	printf ("  if (c == CONSTRAINT_%s)\n", c->c_name);
+	printf ("    return %d;\n", get_register_filter_id (c->filter));
+      }
+  printf ("  return -1;\n"
+	  "}\n");
+}
+
 /* Write tm-preds.h.  Unfortunately, it is impossible to forward-declare
    an enumeration in portable C, so we have to condition all these
    prototypes on HAVE_MACHINE_MODES.  */
@@ -1425,6 +1506,53 @@ write_tm_preds_h (void)
 
   puts ("#endif /* HAVE_MACHINE_MODES */\n");
 
+  /* Print the definition of the target_constraints structure.  */
+  printf ("#ifdef GCC_HARD_REG_SET_H\n"
+	  "struct target_constraints {\n"
+	  "  HARD_REG_SET register_filters[%d];\n",
+	  MAX (register_filters.length (), 1));
+  printf ("};\n"
+	  "\n"
+	  "extern struct target_constraints default_target_constraints;\n"
+	  "#if SWITCHABLE_TARGET\n"
+	  "extern struct target_constraints *this_target_constraints;\n"
+	  "#else\n"
+	  "#define this_target_constraints (&default_target_constraints)\n"
+	  "#endif\n");
+
+  /* Print TEST_REGISTER_FILTER_BIT, which tests whether register REGNO
+     is a valid start register for register filter ID.  */
+  printf ("\n"
+	  "#define TEST_REGISTER_FILTER_BIT(ID, REGNO) \\\n");
+  if (register_filters.is_empty ())
+    printf ("  ((void) (ID), (void) (REGNO), false)\n");
+  else
+    printf ("  TEST_HARD_REG_BIT ("
+	    "this_target_constraints->register_filters[ID], REGNO)\n");
+
+  /* Print test_register_filters, which tests whether register REGNO
+     is a valid start register for the mask of register filters in MASK.  */
+  printf ("\n"
+	  "inline bool\n"
+	  "test_register_filters (unsigned int%s, unsigned int%s)\n",
+	  register_filters.is_empty () ? "" : " mask",
+	  register_filters.is_empty () ? "" : " regno");
+  printf ("{\n");
+  if (register_filters.is_empty ())
+    printf ("  return true;\n");
+  else
+    {
+      printf ("  for (unsigned int id = 0; id < %d; ++id)\n",
+	      register_filters.length ());
+      printf ("    if ((mask & (1U << id))\n"
+	      "\t&& !TEST_REGISTER_FILTER_BIT (id, regno))\n"
+	      "      return false;\n"
+	      "  return true;\n");
+    }
+  printf ("}\n"
+	  "#endif\n"
+	  "\n");
+
   if (constraint_max_namelen > 0)
     {
       write_enum_constraint_num ();
@@ -1548,6 +1676,9 @@ write_tm_preds_h (void)
 	values.safe_push (std::make_pair (address_end, "CT_FIXED_FORM"));
       print_type_tree (values, 0, values.length (), "CT_REGISTER", 2);
       puts ("}");
+
+      write_get_register_filter ();
+      write_get_register_filter_id ();
     }
 
   puts ("#endif /* tm-preds.h */");
@@ -1599,6 +1730,13 @@ write_insn_preds_c (void)
 #include \"tm-constrs.h\"\n\
 #include \"target.h\"\n");
 
+  printf ("\n"
+	  "struct target_constraints default_target_constraints;\n"
+	  "#if SWITCHABLE_TARGET\n"
+	  "struct target_constraints *this_target_constraints"
+	  " = &default_target_constraints;\n"
+	  "#endif\n");
+
   FOR_ALL_PREDICATES (p)
     write_one_predicate_function (p);
 
@@ -1613,6 +1751,8 @@ write_insn_preds_c (void)
       if (have_const_int_constraints)
 	write_insn_const_int_ok_for_constraint ();
     }
+
+  write_init_reg_class_start_regs ();
 }
 
 /* Argument parsing.  */
diff --git a/gcc/gensupport.cc b/gcc/gensupport.cc
index 688808c7d12..0ac0d0772d4 100644
--- a/gcc/gensupport.cc
+++ b/gcc/gensupport.cc
@@ -400,6 +400,45 @@ process_define_predicate (rtx desc, file_location loc)
 #undef I
 #undef N
 #undef Y
+
+/* Maps register filter conditions to the associated filter identifier.  */
+static hash_map<nofree_string_hash, unsigned int> register_filter_map;
+
+/* All register filter conditions, indexed by identifier.  */
+vec<const char *> register_filters;
+
+/* Return the unique identifier for filter condition FILTER.  Identifiers
+   are assigned automatically when the define_register_constraint is
+   parsed.  */
+
+unsigned int
+get_register_filter_id (const char *filter)
+{
+  unsigned int *slot = register_filter_map.get (filter);
+  gcc_assert (slot);
+  return *slot;
+}
+
+/* Process define_register_constraint directive DESC, at location LOC.  */
+
+static void
+process_define_register_constraint (rtx desc, file_location loc)
+{
+  /* Assign identifiers to each unique register filter condition.  */
+  if (const char *filter = XSTR (desc, 3))
+    {
+      bool existed = false;
+      unsigned int &id = register_filter_map.get_or_insert (filter, &existed);
+      if (!existed)
+	{
+	  id = register_filters.length ();
+	  if (id == 32)
+	    fatal_at (loc, "too many distinct register filters, maximum"
+		      " is 32");
+	  register_filters.safe_push (filter);
+	}
+    }
+}
 \f
 /* Queue PATTERN on LIST_TAIL.  Return the address of the new queue
    element.  */
@@ -1075,10 +1114,15 @@ process_rtx (rtx desc, file_location loc)
     case DEFINE_PREDICATE:
     case DEFINE_SPECIAL_PREDICATE:
       process_define_predicate (desc, loc);
-      /* Fall through.  */
+      queue_pattern (desc, &define_pred_tail, loc);
+      break;
 
-    case DEFINE_CONSTRAINT:
     case DEFINE_REGISTER_CONSTRAINT:
+      process_define_register_constraint (desc, loc);
+      queue_pattern (desc, &define_pred_tail, loc);
+      break;
+
+    case DEFINE_CONSTRAINT:
     case DEFINE_MEMORY_CONSTRAINT:
     case DEFINE_SPECIAL_MEMORY_CONSTRAINT:
     case DEFINE_RELAXED_MEMORY_CONSTRAINT:
diff --git a/gcc/gensupport.h b/gcc/gensupport.h
index 7396118714b..27e8444a745 100644
--- a/gcc/gensupport.h
+++ b/gcc/gensupport.h
@@ -108,6 +108,9 @@ struct optab_def
 extern optab_def optabs[];
 extern unsigned int num_optabs;
 
+extern vec<const char *> register_filters;
+extern unsigned int get_register_filter_id (const char *);
+
 /* Information about an instruction name that matches an optab pattern.  */
 struct optab_pattern
 {
diff --git a/gcc/reginfo.cc b/gcc/reginfo.cc
index d472a35946a..5b6e706b35d 100644
--- a/gcc/reginfo.cc
+++ b/gcc/reginfo.cc
@@ -140,6 +140,9 @@ reginfo_cc_finalize (void)
   CLEAR_HARD_REG_SET (global_reg_set);
 }
 
+/* In insn-preds.cc.  */
+extern void init_reg_class_start_regs ();
+
 /* Given a register bitmap, turn on the bits in a HARD_REG_SET that
    correspond to the hard registers, if any, set in that map.  This
    could be done far more efficiently by having all sorts of special-cases
@@ -198,6 +201,8 @@ init_reg_sets (void)
 
   SET_HARD_REG_SET (accessible_reg_set);
   SET_HARD_REG_SET (operand_reg_set);
+
+  init_reg_class_start_regs ();
 }
 
 /* We need to save copies of some of the register information which
diff --git a/gcc/rtl.def b/gcc/rtl.def
index 88e2b198503..a40e1a7bb18 100644
--- a/gcc/rtl.def
+++ b/gcc/rtl.def
@@ -1016,8 +1016,10 @@ DEF_RTL_EXPR(DEFINE_SPECIAL_PREDICATE, "define_special_predicate", "ses", RTX_EX
       at -m switches and the like.
    2: A docstring for this constraint, in Texinfo syntax; not currently
       used, in future will be incorporated into the manual's list of
-      machine-specific operand constraints.  */
-DEF_RTL_EXPR(DEFINE_REGISTER_CONSTRAINT, "define_register_constraint", "sss", RTX_EXTRA)
+      machine-specific operand constraints.
+   3: A C expression that evalutes to true if "regno" is a valid
+      start register.  */
+DEF_RTL_EXPR(DEFINE_REGISTER_CONSTRAINT, "define_register_constraint", "sssS", RTX_EXTRA)
 
 /* Definition of a non-register operand constraint.  These look at the
    operand and decide whether it fits the constraint.
diff --git a/gcc/target-globals.cc b/gcc/target-globals.cc
index 81244b127fc..cfa0045e02c 100644
--- a/gcc/target-globals.cc
+++ b/gcc/target-globals.cc
@@ -41,6 +41,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "bb-reorder.h"
 #include "lower-subreg.h"
 #include "function-abi.h"
+#include "tm_p.h"
 
 #if SWITCHABLE_TARGET
 class target_globals default_target_globals = {
@@ -60,7 +61,8 @@ class target_globals default_target_globals = {
   &default_target_builtins,
   &default_target_gcse,
   &default_target_bb_reorder,
-  &default_target_lower_subreg
+  &default_target_lower_subreg,
+  &default_target_constraints
 };
 
 class target_globals *
@@ -84,6 +86,7 @@ save_target_globals (void)
   g->gcse = XCNEW (struct target_gcse);
   g->bb_reorder = XCNEW (struct target_bb_reorder);
   g->lower_subreg = XCNEW (struct target_lower_subreg);
+  g->constraints = XCNEW (target_constraints);
   restore_target_globals (g);
   init_reg_sets ();
   target_reinit ();
@@ -141,6 +144,7 @@ target_globals::~target_globals ()
       XDELETE (gcse);
       XDELETE (bb_reorder);
       XDELETE (lower_subreg);
+      XDELETE (constraints);
     }
 }
 
diff --git a/gcc/target-globals.h b/gcc/target-globals.h
index daedf66017f..42f082c589c 100644
--- a/gcc/target-globals.h
+++ b/gcc/target-globals.h
@@ -38,6 +38,7 @@ extern struct target_builtins *this_target_builtins;
 extern struct target_gcse *this_target_gcse;
 extern struct target_bb_reorder *this_target_bb_reorder;
 extern struct target_lower_subreg *this_target_lower_subreg;
+extern struct target_constraints *this_target_constraints;
 #endif
 
 class GTY(()) target_globals {
@@ -61,6 +62,7 @@ public:
   struct target_gcse *GTY((skip)) gcse;
   struct target_bb_reorder *GTY((skip)) bb_reorder;
   struct target_lower_subreg *GTY((skip)) lower_subreg;
+  struct target_constraints *GTY((skip)) constraints;
 };
 
 #if SWITCHABLE_TARGET
@@ -89,6 +91,7 @@ restore_target_globals (class target_globals *g)
   this_target_gcse = g->gcse;
   this_target_bb_reorder = g->bb_reorder;
   this_target_lower_subreg = g->lower_subreg;
+  this_target_constraints = g->constraints;
 }
 #endif