[Patch 5/17] Add -fpermitted-flt-eval-methods=[c11|ts-18661-3]

gcc/c-family/

	* c-opts.c (c_common_post_options): Add logic to handle the default
	case for -fpermitted-flt-eval-methods.

gcc/

	* common.opt (fpermitted-flt-eval-methods): New.
	* doc/invoke.texi (-fpermitted-flt-eval-methods): Document it.
	* flag_types.h (permitted_flt_eval_methods): New.

gcc/testsuite/

	* gcc.dg/fpermitted-flt-eval-methods_1.c: New.
	* gcc.dg/fpermitted-flt-eval-methods_2.c: New.

From-SVN: r242775

gcc/ChangeLog

 2016-11-23  James Greenhalgh  <james.greenhalgh@arm.com>
 
+	* common.opt (fpermitted-flt-eval-methods): New.
+	* doc/invoke.texi (-fpermitted-flt-eval-methods): Document it.
+	* flag_types.h (permitted_flt_eval_methods): New.
+
+2016-11-23  James Greenhalgh  <james.greenhalgh@arm.com>
+
 	* config/m68k/m68k.c (m68k_excess_precision): New.
 	(TARGET_C_EXCESS_PRECISION): Define.
 

gcc/c-family/ChangeLog

+2016-11-23  James Greenhalgh  <james.greenhalgh@arm.com>
+
+	* c-opts.c (c_common_post_options): Add logic to handle the default
+	case for -fpermitted-flt-eval-methods.
+
 2016-11-23  Paolo Bonzini  <bonzini@gnu.org>
 
 	* c.opt (Wexpansion-to-defined): New.

gcc/c-family/c-opts.c

@@ -788,6 +788,18 @@ c_common_post_options (const char **pfilename)
       && flag_unsafe_math_optimizations == 0)
     flag_fp_contract_mode = FP_CONTRACT_OFF;
 
+  /* If we are compiling C, and we are outside of a standards mode,
+     we can permit the new values from ISO/IEC TS 18661-3 for
+     FLT_EVAL_METHOD.  Otherwise, we must restrict the possible values to
+     the set specified in ISO C99/C11.  */
+  if (!flag_iso
+      && !c_dialect_cxx ()
+      && (global_options_set.x_flag_permitted_flt_eval_methods
+	  == PERMITTED_FLT_EVAL_METHODS_DEFAULT))
+    flag_permitted_flt_eval_methods = PERMITTED_FLT_EVAL_METHODS_TS_18661;
+  else
+    flag_permitted_flt_eval_methods = PERMITTED_FLT_EVAL_METHODS_C11;
+
   /* By default we use C99 inline semantics in GNU99 or C99 mode.  C99
      inline semantics are not supported in GNU89 or C89 mode.  */
   if (flag_gnu89_inline == -1)

gcc/common.opt

@@ -1326,6 +1326,21 @@ Enum(excess_precision) String(fast) Value(EXCESS_PRECISION_FAST)
 EnumValue
 Enum(excess_precision) String(standard) Value(EXCESS_PRECISION_STANDARD)
 
+; Whether we permit the extended set of values for FLT_EVAL_METHOD
+; introduced in ISO/IEC TS 18661-3, or limit ourselves to those in C99/C11.
+fpermitted-flt-eval-methods=
+Common Joined RejectNegative Enum(permitted_flt_eval_methods) Var(flag_permitted_flt_eval_methods) Init(PERMITTED_FLT_EVAL_METHODS_DEFAULT)
+-fpermitted-flt-eval-methods=[c11|ts-18661]	Specify which values of FLT_EVAL_METHOD are permitted.
+
+Enum
+Name(permitted_flt_eval_methods) Type(enum permitted_flt_eval_methods) UnknownError(unknown specification for the set of FLT_EVAL_METHOD values to permit %qs)
+
+EnumValue
+Enum(permitted_flt_eval_methods) String(c11) Value(PERMITTED_FLT_EVAL_METHODS_C11)
+
+EnumValue
+Enum(permitted_flt_eval_methods) String(ts-18661-3) Value(PERMITTED_FLT_EVAL_METHODS_TS_18661)
+
 ffast-math
 Common Optimization
 

gcc/doc/invoke.texi

@@ -178,6 +178,7 @@ in the following sections.
 @item C Language Options
 @xref{C Dialect Options,,Options Controlling C Dialect}.
 @gccoptlist{-ansi  -std=@var{standard}  -fgnu89-inline @gol
+-fpermitted-flt-eval-methods=@var{standard} @gol
 -aux-info @var{filename} -fallow-parameterless-variadic-functions @gol
 -fno-asm  -fno-builtin  -fno-builtin-@var{function} -fgimple@gol
 -fhosted  -ffreestanding -fopenacc -fopenmp -fopenmp-simd @gol
@@ -1867,6 +1868,30 @@ The preprocessor macros @code{__GNUC_GNU_INLINE__} and
 in effect for @code{inline} functions.  @xref{Common Predefined
 Macros,,,cpp,The C Preprocessor}.
 
+@item -fpermitted-flt-eval-methods=@var{style}
+@opindex fpermitted-flt-eval-methods
+@opindex fpermitted-flt-eval-methods=c11
+@opindex fpermitted-flt-eval-methods=ts-18661-3
+ISO/IEC TS 18661-3 defines new permissible values for
+@code{FLT_EVAL_METHOD} that indicate that operations and constants with
+a semantic type that is an interchange or extended format should be
+evaluated to the precision and range of that type.  These new values are
+a superset of those permitted under C99/C11, which does not specify the
+meaning of other positive values of @code{FLT_EVAL_METHOD}.  As such, code
+conforming to C11 may not have been written expecting the possibility of
+the new values.
+
+@option{-fpermitted-flt-eval-methods} specifies whether the compiler
+should allow only the values of @code{FLT_EVAL_METHOD} specified in C99/C11,
+or the extended set of values specified in ISO/IEC TS 18661-3.
+
+@var{style} is either @code{c11} or @code{ts-18661-3} as appropriate.
+
+The default when in a standards compliant mode (@option{-std=c11} or similar)
+is @option{-fpermitted-flt-eval-methods=c11}.  The default when in a GNU
+dialect (@option{-std=gnu11} or similar) is
+@option{-fpermitted-flt-eval-methods=ts-18661-3}.
+
 @item -aux-info @var{filename}
 @opindex aux-info
 Output to the given filename prototyped declarations for all functions

gcc/flag-types.h

@@ -158,6 +158,14 @@ enum excess_precision
   EXCESS_PRECISION_STANDARD
 };
 
+/* The options for which values of FLT_EVAL_METHOD are permissible.  */
+enum permitted_flt_eval_methods
+{
+  PERMITTED_FLT_EVAL_METHODS_DEFAULT,
+  PERMITTED_FLT_EVAL_METHODS_TS_18661,
+  PERMITTED_FLT_EVAL_METHODS_C11
+};
+
 /* Type of stack check.  */
 enum stack_check_type
 {

gcc/testsuite/ChangeLog

+2016-11-23  James Greenhalgh  <james.greenhalgh@arm.com>
+
+	* gcc.dg/fpermitted-flt-eval-methods_1.c: New.
+	* gcc.dg/fpermitted-flt-eval-methods_2.c: New.
+
 2016-11-23  Martin Sebor  <msebor@redhat.com>
 
 	PR middle-end/78461

gcc/testsuite/gcc.dg/fpermitted-flt-eval-methods_1.c

+/* { dg-do run } */
+/* { dg-options "-std=c11" } */
+
+/* Test that we only see the C99/C11 values for __FLT_EVAL_METHOD__ if
+   we are compiling with -std=c11.  */
+
+int main (int argc, char** argv)
+{
+  switch (__FLT_EVAL_METHOD__)
+    {
+      case 0:
+      case 1:
+      case 2:
+      case -1:
+	return 0;
+      default:
+	return 1;
+    }
+}

gcc/testsuite/gcc.dg/fpermitted-flt-eval-methods_2.c

+/* { dg-do run } */
+/* { dg-options "-fpermitted-flt-eval-methods=c11" } */
+
+/* Test that we only see the C99/C11 values for __FLT_EVAL_METHOD__ if
+   we are compiling with -fpermitted-flt-eval-methods=c11.  */
+
+int main (int argc, char** argv)
+{
+  switch (__FLT_EVAL_METHOD__)
+    {
+      case 0:
+      case 1:
+      case 2:
+      case -1:
+	return 0;
+      default:
+	return 1;
+    }
+}