7 files changed, 62 insertions, 0 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 98678e2..7cf9720 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,13 @@
+2016-11-23  James Greenhalgh  <james.greenhalgh@arm.com>
+
+	* target.def (excess_precision): New hook.
+	* target.h (flt_eval_method): New.
+	(excess_precision_type): Likewise.
+	* targhooks.c (default_excess_precision): New.
+	* targhooks.h (default_excess_precision): New.
+	* doc/tm.texi.in (TARGET_C_EXCESS_PRECISION): New.
+	* doc/tm.texi: Regenerate.
+
 2016-11-23  Martin Sebor  <msebor@redhat.com>
 
 	PR middle-end/78461
diff --git a/gcc/coretypes.h b/gcc/coretypes.h
index 6d78a25..706b9d2 100644
--- a/gcc/coretypes.h
+++ b/gcc/coretypes.h
@@ -332,6 +332,24 @@ enum symbol_visibility
   VISIBILITY_INTERNAL
 };
 
+/* enums used by the targetm.excess_precision hook.  */
+
+enum flt_eval_method
+{
+  FLT_EVAL_METHOD_UNPREDICTABLE = -1,
+  FLT_EVAL_METHOD_PROMOTE_TO_FLOAT = 0,
+  FLT_EVAL_METHOD_PROMOTE_TO_DOUBLE = 1,
+  FLT_EVAL_METHOD_PROMOTE_TO_LONG_DOUBLE = 2,
+  FLT_EVAL_METHOD_PROMOTE_TO_FLOAT16 = 16
+};
+
+enum excess_precision_type
+{
+  EXCESS_PRECISION_TYPE_IMPLICIT,
+  EXCESS_PRECISION_TYPE_STANDARD,
+  EXCESS_PRECISION_TYPE_FAST
+};
+
 /* Support for user-provided GGC and PCH markers.  The first parameter
    is a pointer to a pointer, the second a cookie.  */
 typedef void (*gt_pointer_operator) (void *, void *);
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 7bf09d1..144e63f 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -947,6 +947,10 @@ sign-extend the result to 64 bits.  On such machines, set
 Do not define this macro if it would never modify @var{m}.
 @end defmac
 
+@deftypefn {Target Hook} {enum flt_eval_method} TARGET_C_EXCESS_PRECISION (enum excess_precision_type @var{type})
+Return a value, with the same meaning as @code{FLT_EVAL_METHOD} C that describes which excess precision should be applied.  @var{type} is either @code{EXCESS_PRECISION_TYPE_IMPLICIT}, @code{EXCESS_PRECISION_TYPE_FAST}, or @code{EXCESS_PRECISION_TYPE_STANDARD}.  For @code{EXCESS_PRECISION_TYPE_IMPLICIT}, the target should return which precision and range operations will be implictly evaluated in regardless of the excess precision explicitly added.  For @code{EXCESS_PRECISION_TYPE_STANDARD} and @code{EXCESS_PRECISION_TYPE_FAST}, the target should return the explicit excess precision that should be added depending on the value set for @option{-fexcess-precision=@r{[}standard@r{|}fast@r{]}}.
+@end deftypefn
+
 @deftypefn {Target Hook} machine_mode TARGET_PROMOTE_FUNCTION_MODE (const_tree @var{type}, machine_mode @var{mode}, int *@var{punsignedp}, const_tree @var{funtype}, int @var{for_return})
 Like @code{PROMOTE_MODE}, but it is applied to outgoing function arguments or
 function return values.  The target hook should return the new mode
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 58d1e63..7d8dcff 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -921,6 +921,8 @@ sign-extend the result to 64 bits.  On such machines, set
 Do not define this macro if it would never modify @var{m}.
 @end defmac
 
+@hook TARGET_C_EXCESS_PRECISION
+
 @hook TARGET_PROMOTE_FUNCTION_MODE
 
 @defmac PARM_BOUNDARY
diff --git a/gcc/target.def b/gcc/target.def
index c24b4cf..efcc336 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -5464,6 +5464,23 @@ DEFHOOK_UNDOC
  machine_mode, (char c),
  default_mode_for_suffix)
 
+DEFHOOK
+(excess_precision,
+ "Return a value, with the same meaning as @code{FLT_EVAL_METHOD} C that\
+ describes which excess precision should be applied.  @var{type} is\
+ either @code{EXCESS_PRECISION_TYPE_IMPLICIT},\
+ @code{EXCESS_PRECISION_TYPE_FAST}, or\
+ @code{EXCESS_PRECISION_TYPE_STANDARD}.  For\
+ @code{EXCESS_PRECISION_TYPE_IMPLICIT}, the target should return which\
+ precision and range operations will be implictly evaluated in regardless\
+ of the excess precision explicitly added.  For\
+ @code{EXCESS_PRECISION_TYPE_STANDARD} and\
+ @code{EXCESS_PRECISION_TYPE_FAST}, the target should return the\
+ explicit excess precision that should be added depending on the\
+ value set for @option{-fexcess-precision=@r{[}standard@r{|}fast@r{]}}.",
+ enum flt_eval_method, (enum excess_precision_type type),
+ default_excess_precision)
+
 HOOK_VECTOR_END (c)
 
 /* Functions specific to the C++ frontend.  */
diff --git a/gcc/targhooks.c b/gcc/targhooks.c
index 866747a..73e1c25 100644
--- a/gcc/targhooks.c
+++ b/gcc/targhooks.c
@@ -2135,4 +2135,12 @@ default_min_arithmetic_precision (void)
   return WORD_REGISTER_OPERATIONS ? BITS_PER_WORD : BITS_PER_UNIT;
 }
 
+/* Default implementation of TARGET_C_EXCESS_PRECISION.  */
+
+enum flt_eval_method
+default_excess_precision (enum excess_precision_type ATTRIBUTE_UNUSED)
+{
+  return FLT_EVAL_METHOD_PROMOTE_TO_FLOAT;
+}
+
 #include "gt-targhooks.h"
diff --git a/gcc/targhooks.h b/gcc/targhooks.h
index 94f5e31..e00da60 100644
--- a/gcc/targhooks.h
+++ b/gcc/targhooks.h
@@ -263,4 +263,7 @@ extern bool default_optab_supported_p (int, machine_mode, machine_mode,
 extern unsigned int default_max_noce_ifcvt_seq_cost (edge);
 extern unsigned int default_min_arithmetic_precision (void);
 
+extern enum flt_eval_method
+default_excess_precision (enum excess_precision_type ATTRIBUTE_UNUSED);
+
 #endif /* GCC_TARGHOOKS_H */