diff mbox

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

Message ID 1479117347-33829-1-git-send-email-james.greenhalgh@arm.com
State New
Headers show

Commit Message

James Greenhalgh Nov. 14, 2016, 9:55 a.m. UTC
On Fri, Nov 11, 2016 at 09:42:32PM -0700, Sandra Loosemore wrote:
> On 11/11/2016 08:37 AM, James Greenhalgh wrote:

>

> >diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi

> >index f133b3a..75ff8ec 100644

> >--- a/gcc/doc/invoke.texi

> >+++ b/gcc/doc/invoke.texi

> >@@ -378,7 +378,8 @@ Objective-C and Objective-C++ Dialects}.

> > -flto-partition=@var{alg} -fmerge-all-constants @gol

> > -fmerge-constants -fmodulo-sched -fmodulo-sched-allow-regmoves @gol

> > -fmove-loop-invariants -fno-branch-count-reg @gol

> >--fno-defer-pop -fno-fp-int-builtin-inexact -fno-function-cse @gol

> >+-fno-defer-pop -fno-fp-int-builtin-inexact @gol

> >+-fpermitted-flt-eval-methods=@var{standard} -fno-function-cse @gol

> > -fno-guess-branch-probability -fno-inline -fno-math-errno -fno-peephole @gol

> > -fno-peephole2 -fno-sched-interblock -fno-sched-spec -fno-signed-zeros @gol

> > -fno-toplevel-reorder -fno-trapping-math -fno-zero-initialized-in-bss @gol

>

> This seems like totally the wrong place to document this.  The new

> option seems more like a code generation option than an optimization

> option, which is what the context of the above patch hunk is.

> Moreover, the list above is alphabetized and you're sticking the new

> option in a totally random place within the list.


Oh! Definitely a case of not seeing the wood for the trees there. All
I knew was that the option was a little bit like -fexcess-precision, but
I completely failed to spot that this list was alpahbetised, or even to
see that the list related to optimisation options!

Sorry for that, I've moved it now to "C Language Options" - which as far as
I can tell is not in alphabetical order, I slotted it in after gnu89-inline
as that made sense to me, but I can move it again if you like. Is that
placement more acceptable?

Thanks,
James

---

gcc/c-family/

2016-11-09  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.

gcc/

2016-11-09  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.

gcc/testsuite/

2016-11-09  James Greenhalgh  <james.greenhalgh@arm.com>

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

Comments

Sandra Loosemore Nov. 14, 2016, 11:43 p.m. UTC | #1
On 11/14/2016 02:55 AM, James Greenhalgh wrote:
>

> On Fri, Nov 11, 2016 at 09:42:32PM -0700, Sandra Loosemore wrote:

>> On 11/11/2016 08:37 AM, James Greenhalgh wrote:

>>

>>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi

>>> index f133b3a..75ff8ec 100644

>>> --- a/gcc/doc/invoke.texi

>>> +++ b/gcc/doc/invoke.texi

>>> @@ -378,7 +378,8 @@ Objective-C and Objective-C++ Dialects}.

>>> -flto-partition=@var{alg} -fmerge-all-constants @gol

>>> -fmerge-constants -fmodulo-sched -fmodulo-sched-allow-regmoves @gol

>>> -fmove-loop-invariants -fno-branch-count-reg @gol

>>> --fno-defer-pop -fno-fp-int-builtin-inexact -fno-function-cse @gol

>>> +-fno-defer-pop -fno-fp-int-builtin-inexact @gol

>>> +-fpermitted-flt-eval-methods=@var{standard} -fno-function-cse @gol

>>> -fno-guess-branch-probability -fno-inline -fno-math-errno -fno-peephole @gol

>>> -fno-peephole2 -fno-sched-interblock -fno-sched-spec -fno-signed-zeros @gol

>>> -fno-toplevel-reorder -fno-trapping-math -fno-zero-initialized-in-bss @gol

>>

>> This seems like totally the wrong place to document this.  The new

>> option seems more like a code generation option than an optimization

>> option, which is what the context of the above patch hunk is.

>> Moreover, the list above is alphabetized and you're sticking the new

>> option in a totally random place within the list.

>

> Oh! Definitely a case of not seeing the wood for the trees there. All

> I knew was that the option was a little bit like -fexcess-precision, but

> I completely failed to spot that this list was alpahbetised, or even to

> see that the list related to optimisation options!

>

> Sorry for that, I've moved it now to "C Language Options" - which as far as

> I can tell is not in alphabetical order, I slotted it in after gnu89-inline

> as that made sense to me, but I can move it again if you like. Is that

> placement more acceptable?


Yes, this version of the doc patch looks fine.  Thank you!

-Sandra
diff mbox

Patch

diff --git a/gcc/c-family/c-opts.c b/gcc/c-family/c-opts.c
index de260e7..57717ff 100644
--- a/gcc/c-family/c-opts.c
+++ b/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)
diff --git a/gcc/common.opt b/gcc/common.opt
index 314145a..915c406 100644
--- a/gcc/common.opt
+++ b/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
 
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index eb89804..0ec10ba 100644
--- a/gcc/doc/invoke.texi
+++ b/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} @gol
 -fhosted  -ffreestanding -fopenacc -fopenmp -fopenmp-simd @gol
@@ -1872,6 +1873,30 @@  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
diff --git a/gcc/flag-types.h b/gcc/flag-types.h
index 6c5a4cc..d69f8f4 100644
--- a/gcc/flag-types.h
+++ b/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
 {
diff --git a/gcc/testsuite/gcc.dg/fpermitted-flt-eval-methods_1.c b/gcc/testsuite/gcc.dg/fpermitted-flt-eval-methods_1.c
new file mode 100644
index 0000000..c022f86
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fpermitted-flt-eval-methods_1.c
@@ -0,0 +1,19 @@ 
+/* { 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;
+    }
+}
diff --git a/gcc/testsuite/gcc.dg/fpermitted-flt-eval-methods_2.c b/gcc/testsuite/gcc.dg/fpermitted-flt-eval-methods_2.c
new file mode 100644
index 0000000..a76ea7e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fpermitted-flt-eval-methods_2.c
@@ -0,0 +1,19 @@ 
+/* { 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;
+    }
+}