[PATCH] Fix ARM exception handling (PR target/89093)

[PATCH] Fix ARM exception handling (PR target/89093)

[Jakub Jelinek]

Hi!

As detailed in the PR, unlike most other targets, on ARM EABI the floating
point registers are saved lazily, when EH personality routine calls
__gnu_unwind_frame (usually in the CONTINUE_UNWINDING macro).
That means the unwinder itself and the personality routines (and whatever
other functions those call in the path to CONTINUE_UNWINDING) must be
compiled so that it doesn't use floating point registers.  Calling some
function that saves those on entry and restores on exit is fine, but calling
some function which saves those on entry and then calls __gnu_unwind_frame
and then restores on exit is not fine.
In 8.x and earlier we were just lucky that the RA when compiling those
didn't decide to use any of those registers, but starting with the combiner
hard register changes we are no longer so lucky.

The following patch introduces -mgeneral-regs-only option and
general-regs-only target attribute for ARM (similarly to how other targets
like AArch64 and x86), changes the ARM unwinder to be compiled with that
and changes the personality routines of all languages so that either just
the personality routine, or whatever other routines called by personality
routines that call directly or indirectly __gnu_unwind_frame to be compiled
that way.

Bootstrapped/regtested on armv7hl-linux-gnueabi (and x86_64-linux to make
sure it compiles on other targets too).

Ok for trunk?

While the libgo changes are included in the patch, I think those need to go
through go upstream and will likely need some changes if that code can be
compiled by earlier GCC versions or other compilers.

Not sure about libphobos D stuff, does it need to go through upstream and
is libdruntime/gcc/deh.d compiled by compilers other than GDC?

The Ada changes need those guards because the file is compiled by both
the system compiler and by the newly built compilers; when compiled by
system compiler, as the FE is built with -fno-exceptions I'd hope the EH
stuff isn't really used there and at least until GCC 9.1 is released we have
the issue that the system compiler could be some earlier GCC 9.0.1 snapshot
which doesn't support general-regs-only.

2019-04-22  Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>
	    Bernd Edlinger  <bernd.edlinger@hotmail.de>
	    Jakub Jelinek  <jakub@redhat.com>

	PR target/89093
	* config/arm/arm.c (aapcs_vfp_is_call_or_return_candidate): Diagnose
	if used with general-regs-only.
	(arm_conditional_register_usage): Don't add non-general regs if
	general-regs-only.
	(arm_valid_target_attribute_rec): Handle general-regs-only.
	* config/arm/arm.h (TARGET_HARD_FLOAT): Return false if
	general-regs-only.
	(TARGET_HARD_FLOAT_SUB): Define.
	(TARGET_SOFT_FLOAT): Define as negation of TARGET_HARD_FLOAT_SUB.
	(TARGET_REALLY_IWMMXT): Add && !TARGET_GENERAL_REGS_ONLY.
	(TARGET_REALLY_IWMMXT2): Likewise.
	* config/arm/arm.opt: Add -mgeneral-regs-only.
	* doc/extend.texi: Document ARM general-regs-only target.
	* doc/invoke.texi: Document ARM -mgeneral-regs-only.
gcc/ada/
	* raise-gcc.c (TARGET_ATTRIBUTE): Define.
	(continue_unwind, personality_body, PERSONALITY_FUNCTION): Add
	TARGET_ATTRIBUTE.
libgcc/
	* config/arm/pr-support.c: Add #pragma GCC target("general-regs-only").
	* config/arm/unwind-arm.c: Likewise.
	* unwind-c.c (PERSONALITY_FUNCTION): Add general-regs-only target
	attribute for ARM.
libobjc/
	* exception.c (PERSONALITY_FUNCTION): Add general-regs-only target
	attribute for ARM.
libphobos/
	* libdruntime/gcc/deh.d: Import gcc.attribute.
	(personality_fn_attributes): New enum.
	(scanLSDA, CONTINUE_UNWINDING, gdc_personality, __gdc_personality):
	Add @personality_fn_attributes.
libstdc++-v3/
	* libsupc++/eh_personality.cc (PERSONALITY_FUNCTION): Add
	general-regs-only target attribute for ARM.
libgo/
	* runtime/go-unwind.c (PERSONALITY_FUNCTION,
	__gccgo_personality_dummy): Add general-regs-only target
        attribute for ARM.

--- gcc/config/arm/arm.c	(revision 270444)
+++ gcc/config/arm/arm.c	(working copy)
@@ -6112,6 +6112,11 @@ aapcs_vfp_is_call_or_return_candidate (enum arm_pc
     return false;
 
   *base_mode = new_mode;
+
+  if (TARGET_GENERAL_REGS_ONLY)
+    error ("argument of type %qT not permitted with -mgeneral-regs-only",
+	   type);
+
   return true;
 }
 
@@ -28404,7 +28409,7 @@ arm_conditional_register_usage (void)
 	}
     }
 
-  if (TARGET_REALLY_IWMMXT)
+  if (TARGET_REALLY_IWMMXT && !TARGET_GENERAL_REGS_ONLY)
     {
       regno = FIRST_IWMMXT_GR_REGNUM;
       /* The 2002/10/09 revision of the XScale ABI has wCG0
@@ -30878,6 +30883,9 @@ arm_valid_target_attribute_rec (tree args, struct
       else if (!strcmp (q, "arm"))
 	opts->x_target_flags &= ~MASK_THUMB;
 
+      else if (!strcmp (q, "general-regs-only"))
+	opts->x_target_flags |= MASK_GENERAL_REGS_ONLY;
+
       else if (!strncmp (q, "fpu=", 4))
 	{
 	  int fpu_index;
--- gcc/config/arm/arm.h	(revision 270444)
+++ gcc/config/arm/arm.h	(working copy)
@@ -122,12 +122,18 @@ extern tree arm_fp16_type_node;
 #define TARGET_32BIT_P(flags)  (TARGET_ARM_P (flags) || TARGET_THUMB2_P (flags))
 
 /* Run-time Target Specification.  */
-/* Use hardware floating point instructions. */
-#define TARGET_HARD_FLOAT	(arm_float_abi != ARM_FLOAT_ABI_SOFT	\
+/* Use hardware floating point instructions. -mgeneral-regs-only prevents
+the use of floating point instructions and registers but does not prevent
+emission of floating point pcs attributes.  */
+#define TARGET_HARD_FLOAT_SUB	(arm_float_abi != ARM_FLOAT_ABI_SOFT	\
 				 && bitmap_bit_p (arm_active_target.isa, \
 						  isa_bit_vfpv2) \
 				 && TARGET_32BIT)
-#define TARGET_SOFT_FLOAT	(!TARGET_HARD_FLOAT)
+
+#define TARGET_HARD_FLOAT	(TARGET_HARD_FLOAT_SUB		\
+				 && !TARGET_GENERAL_REGS_ONLY)
+
+#define TARGET_SOFT_FLOAT	(!TARGET_HARD_FLOAT_SUB)
 /* User has permitted use of FP instructions, if they exist for this
    target.  */
 #define TARGET_MAYBE_HARD_FLOAT (arm_float_abi != ARM_FLOAT_ABI_SOFT)
@@ -135,8 +141,10 @@ extern tree arm_fp16_type_node;
 #define TARGET_HARD_FLOAT_ABI		(arm_float_abi == ARM_FLOAT_ABI_HARD)
 #define TARGET_IWMMXT			(arm_arch_iwmmxt)
 #define TARGET_IWMMXT2			(arm_arch_iwmmxt2)
-#define TARGET_REALLY_IWMMXT		(TARGET_IWMMXT && TARGET_32BIT)
-#define TARGET_REALLY_IWMMXT2		(TARGET_IWMMXT2 && TARGET_32BIT)
+#define TARGET_REALLY_IWMMXT		(TARGET_IWMMXT && TARGET_32BIT \
+					 && !TARGET_GENERAL_REGS_ONLY)
+#define TARGET_REALLY_IWMMXT2		(TARGET_IWMMXT2 && TARGET_32BIT \
+					 && !TARGET_GENERAL_REGS_ONLY)
 #define TARGET_IWMMXT_ABI (TARGET_32BIT && arm_abi == ARM_ABI_IWMMXT)
 #define TARGET_ARM                      (! TARGET_THUMB)
 #define TARGET_EITHER			1 /* (TARGET_ARM | TARGET_THUMB) */
--- gcc/config/arm/arm.opt	(revision 270444)
+++ gcc/config/arm/arm.opt	(working copy)
@@ -302,3 +302,7 @@ When linking for big-endian targets, generate a le
 mbranch-cost=
 Target RejectNegative Joined UInteger Var(arm_branch_cost) Init(-1)
 Cost to assume for a branch insn.
+
+mgeneral-regs-only
+Target Report RejectNegative Mask(GENERAL_REGS_ONLY) Save
+Generate code which uses the core registers only (r0-r14).
--- gcc/doc/extend.texi	(revision 270444)
+++ gcc/doc/extend.texi	(working copy)
@@ -4190,6 +4190,15 @@ into the @code{sjli} table needs to be passed as a
 These function attributes are supported for ARM targets:
 
 @table @code
+
+@item general-regs-only
+@cindex @code{general-regs-only} function attribute, ARM
+Indicates that no floating-point or Advanced SIMD registers should be
+used when generating code for this function.  If the function explicitly
+uses floating-point code, then the compiler gives an error.  This is
+the same behavior as that of the command-line option
+@option{-mgeneral-regs-only}.
+
 @item interrupt
 @cindex @code{interrupt} function attribute, ARM
 Use this attribute to indicate
--- gcc/doc/invoke.texi	(revision 270444)
+++ gcc/doc/invoke.texi	(working copy)
@@ -674,6 +674,7 @@ Objective-C and Objective-C++ Dialects}.
 -mabi=@var{name} @gol
 -mapcs-stack-check  -mno-apcs-stack-check @gol
 -mapcs-reentrant  -mno-apcs-reentrant @gol
+-mgeneral-regs-only @gol
 -msched-prolog  -mno-sched-prolog @gol
 -mlittle-endian  -mbig-endian @gol
 -mbe8  -mbe32 @gol
@@ -17068,6 +17069,12 @@ the hard-float and soft-float ABIs are not link-co
 compile your entire program with the same ABI, and link with a
 compatible set of libraries.
 
+@item -mgeneral-regs-only
+@opindex mgeneral-regs-only
+Generate code which uses only the general-purpose registers.  This will prevent
+the compiler from using floating-point and Advanced SIMD registers but will not
+impose any restrictions on the assembler.
+
 @item -mlittle-endian
 @opindex mlittle-endian
 Generate code for a processor running in little-endian mode.  This is
--- gcc/ada/raise-gcc.c	(revision 270444)
+++ gcc/ada/raise-gcc.c	(working copy)
@@ -1154,10 +1154,18 @@ extern void __gnat_notify_unhandled_exce
 #define PERSONALITY_FUNCTION    __gnat_personality_v0
 #endif
 
+#if defined (__ARM_EABI_UNWINDER__) \
+    && (defined (IN_RTS) || GCC_VERSION > 9000)
+#define TARGET_ATTRIBUTE __attribute__((target ("general-regs-only")))
+#else
+#define TARGET_ATTRIBUTE
+#endif
+
 /* Code executed to continue unwinding.  With the ARM unwinder, the
    personality routine must unwind one frame (per EHABI 7.3 4.).  */
 
 static _Unwind_Reason_Code
+TARGET_ATTRIBUTE
 continue_unwind (struct _Unwind_Exception* ue_header ATTRIBUTE_UNUSED,
 		 struct _Unwind_Context* uw_context ATTRIBUTE_UNUSED)
 {
@@ -1172,6 +1180,7 @@ continue_unwind (struct _Unwind_Exceptio
    between all unwinders.  */
 
 static _Unwind_Reason_Code
+TARGET_ATTRIBUTE
 personality_body (_Unwind_Action uw_phases,
 		  _Unwind_Exception *uw_exception,
 		  _Unwind_Context *uw_context)
@@ -1342,6 +1351,7 @@ PERSONALITY_FUNCTION (_Unwind_State stat
 		      struct _Unwind_Context* uw_context);
 
 PERSONALITY_STORAGE _Unwind_Reason_Code
+TARGET_ATTRIBUTE
 PERSONALITY_FUNCTION (_Unwind_State state,
 		      struct _Unwind_Exception* uw_exception,
 		      struct _Unwind_Context* uw_context)
--- libgcc/config/arm/pr-support.c	(revision 270444)
+++ libgcc/config/arm/pr-support.c	(working copy)
@@ -21,6 +21,7 @@
    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
    <http://www.gnu.org/licenses/>.  */
 
+#pragma GCC target ("general-regs-only")
 #include "unwind.h"
 
 /* We add a prototype for abort here to avoid creating a dependency on
--- libgcc/config/arm/unwind-arm.c	(revision 270444)
+++ libgcc/config/arm/unwind-arm.c	(working copy)
@@ -21,6 +21,7 @@
    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
    <http://www.gnu.org/licenses/>.  */
 
+#pragma GCC target ("general-regs-only")
 #include "unwind.h"
 
 /* Misc constants.  */
--- libgcc/unwind-c.c	(revision 270444)
+++ libgcc/unwind-c.c	(working copy)
@@ -106,6 +106,7 @@ PERSONALITY_FUNCTION (_Unwind_State, struct _Unwin
 		      struct _Unwind_Context *);
 
 _Unwind_Reason_Code
+__attribute__((target ("general-regs-only")))
 PERSONALITY_FUNCTION (_Unwind_State state,
 		      struct _Unwind_Exception * ue_header,
 		      struct _Unwind_Context * context)
--- libgo/runtime/go-unwind.c	(revision 270444)
+++ libgo/runtime/go-unwind.c	(working copy)
@@ -411,7 +411,7 @@ parse_lsda_header (struct _Unwind_Contex
 _Unwind_Reason_Code
 PERSONALITY_FUNCTION (_Unwind_State, struct _Unwind_Exception *,
 		      struct _Unwind_Context *)
-  __attribute__ ((no_split_stack, flatten));
+  __attribute__ ((no_split_stack, flatten, target ("general-regs-only")));
 
 _Unwind_Reason_Code
 PERSONALITY_FUNCTION (_Unwind_State state,
@@ -604,6 +604,9 @@ __gccgo_personality_dummy (int, _Unwind_
   __attribute__ ((no_split_stack));
 
 _Unwind_Reason_Code
+#ifdef __ARM_EABI_UNWINDER__
+__attribute__ ((target ("general-regs-only")))
+#endif
 __gccgo_personality_dummy (int version __attribute__ ((unused)),
 		      _Unwind_Action actions __attribute__ ((unused)),
 		      _Unwind_Exception_Class exception_class __attribute__ ((unused)),
--- libobjc/exception.c	(revision 270444)
+++ libobjc/exception.c	(working copy)
@@ -220,6 +220,7 @@ get_ttype_entry (struct lsda_header_info *info, _U
   while (0)
 
 _Unwind_Reason_Code
+__attribute__((target ("general-regs-only")))
 PERSONALITY_FUNCTION (_Unwind_State state,
 		      struct _Unwind_Exception *ue_header,
 		      struct _Unwind_Context *context)
--- libphobos/libdruntime/gcc/deh.d	(revision 270444)
+++ libphobos/libdruntime/gcc/deh.d	(working copy)
@@ -28,6 +28,7 @@ import gcc.unwind;
 import gcc.unwind.pe;
 import gcc.builtins;
 import gcc.config;
+import gcc.attribute;
 
 extern(C)
 {
@@ -519,10 +520,19 @@ extern(C) void _d_throw(Throwable object)
     terminate("unwind error", __LINE__);
 }
 
+static if (GNU_ARM_EABI_Unwinder)
+{
+    enum personality_fn_attributes = attribute("target", ("general-regs-only"));
+}
+else
+{
+    enum personality_fn_attributes = "";
+}
 
 /**
  * Read and extract information from the LSDA (.gcc_except_table section).
  */
+@personality_fn_attributes
 _Unwind_Reason_Code scanLSDA(const(ubyte)* lsda, _Unwind_Exception_Class exceptionClass,
                              _Unwind_Action actions, _Unwind_Exception* unwindHeader,
                              _Unwind_Context* context, _Unwind_Word cfa,
@@ -772,6 +782,7 @@ int actionTableLookup(_Unwind_Action actions, _Unw
  * Called when the personality function has found neither a cleanup or handler.
  * To support ARM EABI personality routines, that must also unwind the stack.
  */
+@personality_fn_attributes
 _Unwind_Reason_Code CONTINUE_UNWINDING(_Unwind_Exception* unwindHeader, _Unwind_Context* context)
 {
     static if (GNU_ARM_EABI_Unwinder)
@@ -814,6 +825,7 @@ else
 static if (GNU_ARM_EABI_Unwinder)
 {
     pragma(mangle, PERSONALITY_FUNCTION)
+    @personality_fn_attributes
     extern(C) _Unwind_Reason_Code gdc_personality(_Unwind_State state,
                                                   _Unwind_Exception* unwindHeader,
                                                   _Unwind_Context* context)
@@ -873,6 +885,7 @@ else
     }
 }
 
+@personality_fn_attributes
 private _Unwind_Reason_Code __gdc_personality(_Unwind_Action actions,
                                               _Unwind_Exception_Class exceptionClass,
                                               _Unwind_Exception* unwindHeader,
--- libstdc++-v3/libsupc++/eh_personality.cc	(revision 270444)
+++ libstdc++-v3/libsupc++/eh_personality.cc	(working copy)
@@ -343,6 +343,7 @@ extern "C"
 #endif
 _Unwind_Reason_Code
 #ifdef __ARM_EABI_UNWINDER__
+__attribute__((target ("general-regs-only")))
 PERSONALITY_FUNCTION (_Unwind_State state,
 		      struct _Unwind_Exception* ue_header,
 		      struct _Unwind_Context* context)

	Jakub

Re: [PATCH] Fix ARM exception handling (PR target/89093)

[Iain Buclaw]

On Mon, 22 Apr 2019 at 11:15, Jakub Jelinek <jakub@redhat.com> wrote:
>
> Not sure about libphobos D stuff, does it need to go through upstream and
> is libdruntime/gcc/deh.d compiled by compilers other than GDC?
>

It is not part of upstream, I could make that clearer in
libphobos/README.gcc if there's uncertainty.

> --- libphobos/libdruntime/gcc/deh.d     (revision 270444)
> +++ libphobos/libdruntime/gcc/deh.d     (working copy)
> @@ -28,6 +28,7 @@ import gcc.unwind;
>  import gcc.unwind.pe;
>  import gcc.builtins;
>  import gcc.config;
> +import gcc.attribute;
>
>  extern(C)
>  {
> @@ -519,10 +520,19 @@ extern(C) void _d_throw(Throwable object)
>      terminate("unwind error", __LINE__);
>  }
>
> +static if (GNU_ARM_EABI_Unwinder)
> +{
> +    enum personality_fn_attributes = attribute("target", ("general-regs-only"));
> +}
> +else
> +{
> +    enum personality_fn_attributes = "";
> +}
>
>  /**
>   * Read and extract information from the LSDA (.gcc_except_table section).
>   */
> +@personality_fn_attributes
>  _Unwind_Reason_Code scanLSDA(const(ubyte)* lsda, _Unwind_Exception_Class exceptionClass,
>                               _Unwind_Action actions, _Unwind_Exception* unwindHeader,
>                               _Unwind_Context* context, _Unwind_Word cfa,
> @@ -772,6 +782,7 @@ int actionTableLookup(_Unwind_Action actions, _Unw
>   * Called when the personality function has found neither a cleanup or handler.
>   * To support ARM EABI personality routines, that must also unwind the stack.
>   */
> +@personality_fn_attributes
>  _Unwind_Reason_Code CONTINUE_UNWINDING(_Unwind_Exception* unwindHeader, _Unwind_Context* context)
>  {
>      static if (GNU_ARM_EABI_Unwinder)
> @@ -814,6 +825,7 @@ else
>  static if (GNU_ARM_EABI_Unwinder)
>  {
>      pragma(mangle, PERSONALITY_FUNCTION)
> +    @personality_fn_attributes
>      extern(C) _Unwind_Reason_Code gdc_personality(_Unwind_State state,
>                                                    _Unwind_Exception* unwindHeader,
>                                                    _Unwind_Context* context)
> @@ -873,6 +885,7 @@ else
>      }
>  }
>
> +@personality_fn_attributes
>  private _Unwind_Reason_Code __gdc_personality(_Unwind_Action actions,
>                                                _Unwind_Exception_Class exceptionClass,
>                                                _Unwind_Exception* unwindHeader,

No problem with this part from myself.

-- 
Iain

Re: [PATCH] Fix ARM exception handling (PR target/89093)

[Ramana Radhakrishnan]

On Mon, Apr 22, 2019 at 10:15 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> Hi!
>
> As detailed in the PR, unlike most other targets, on ARM EABI the floating
> point registers are saved lazily, when EH personality routine calls
> __gnu_unwind_frame (usually in the CONTINUE_UNWINDING macro).
> That means the unwinder itself and the personality routines (and whatever
> other functions those call in the path to CONTINUE_UNWINDING) must be
> compiled so that it doesn't use floating point registers.  Calling some
> function that saves those on entry and restores on exit is fine, but calling
> some function which saves those on entry and then calls __gnu_unwind_frame
> and then restores on exit is not fine.
> In 8.x and earlier we were just lucky that the RA when compiling those
> didn't decide to use any of those registers, but starting with the combiner
> hard register changes we are no longer so lucky.
>
> The following patch introduces -mgeneral-regs-only option and
> general-regs-only target attribute for ARM (similarly to how other targets
> like AArch64 and x86), changes the ARM unwinder to be compiled with that
> and changes the personality routines of all languages so that either just
> the personality routine, or whatever other routines called by personality
> routines that call directly or indirectly __gnu_unwind_frame to be compiled
> that way.
>
> Bootstrapped/regtested on armv7hl-linux-gnueabi (and x86_64-linux to make
> sure it compiles on other targets too).
>
> Ok for trunk?

Ok. Thanks a lot for working on this and fixing the rest of this up.
I've been busy with a few other things.


> While the libgo changes are included in the patch, I think those need to go
> through go upstream and will likely need some changes if that code can be
> compiled by earlier GCC versions or other compilers.
>




> Not sure about libphobos D stuff, does it need to go through upstream and
> is libdruntime/gcc/deh.d compiled by compilers other than GDC?
>
> The Ada changes need those guards because the file is compiled by both
> the system compiler and by the newly built compilers; when compiled by
> system compiler, as the FE is built with -fno-exceptions I'd hope the EH
> stuff isn't really used there and at least until GCC 9.1 is released we have
> the issue that the system compiler could be some earlier GCC 9.0.1 snapshot
> which doesn't support general-regs-only.

I don't grok enough ada to approve this and will leave that part to
Eric or others.

Ramana

>
> 2019-04-22  Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>
>             Bernd Edlinger  <bernd.edlinger@hotmail.de>
>             Jakub Jelinek  <jakub@redhat.com>
>
>         PR target/89093
>         * config/arm/arm.c (aapcs_vfp_is_call_or_return_candidate): Diagnose
>         if used with general-regs-only.
>         (arm_conditional_register_usage): Don't add non-general regs if
>         general-regs-only.
>         (arm_valid_target_attribute_rec): Handle general-regs-only.
>         * config/arm/arm.h (TARGET_HARD_FLOAT): Return false if
>         general-regs-only.
>         (TARGET_HARD_FLOAT_SUB): Define.
>         (TARGET_SOFT_FLOAT): Define as negation of TARGET_HARD_FLOAT_SUB.
>         (TARGET_REALLY_IWMMXT): Add && !TARGET_GENERAL_REGS_ONLY.
>         (TARGET_REALLY_IWMMXT2): Likewise.
>         * config/arm/arm.opt: Add -mgeneral-regs-only.
>         * doc/extend.texi: Document ARM general-regs-only target.
>         * doc/invoke.texi: Document ARM -mgeneral-regs-only.
> gcc/ada/
>         * raise-gcc.c (TARGET_ATTRIBUTE): Define.
>         (continue_unwind, personality_body, PERSONALITY_FUNCTION): Add
>         TARGET_ATTRIBUTE.
> libgcc/
>         * config/arm/pr-support.c: Add #pragma GCC target("general-regs-only").
>         * config/arm/unwind-arm.c: Likewise.
>         * unwind-c.c (PERSONALITY_FUNCTION): Add general-regs-only target
>         attribute for ARM.
> libobjc/
>         * exception.c (PERSONALITY_FUNCTION): Add general-regs-only target
>         attribute for ARM.
> libphobos/
>         * libdruntime/gcc/deh.d: Import gcc.attribute.
>         (personality_fn_attributes): New enum.
>         (scanLSDA, CONTINUE_UNWINDING, gdc_personality, __gdc_personality):
>         Add @personality_fn_attributes.
> libstdc++-v3/
>         * libsupc++/eh_personality.cc (PERSONALITY_FUNCTION): Add
>         general-regs-only target attribute for ARM.
> libgo/
>         * runtime/go-unwind.c (PERSONALITY_FUNCTION,
>         __gccgo_personality_dummy): Add general-regs-only target
>         attribute for ARM.
>
> --- gcc/config/arm/arm.c        (revision 270444)
> +++ gcc/config/arm/arm.c        (working copy)
> @@ -6112,6 +6112,11 @@ aapcs_vfp_is_call_or_return_candidate (enum arm_pc
>      return false;
>
>    *base_mode = new_mode;
> +
> +  if (TARGET_GENERAL_REGS_ONLY)
> +    error ("argument of type %qT not permitted with -mgeneral-regs-only",
> +          type);
> +
>    return true;
>  }
>
> @@ -28404,7 +28409,7 @@ arm_conditional_register_usage (void)
>         }
>      }
>
> -  if (TARGET_REALLY_IWMMXT)
> +  if (TARGET_REALLY_IWMMXT && !TARGET_GENERAL_REGS_ONLY)
>      {
>        regno = FIRST_IWMMXT_GR_REGNUM;
>        /* The 2002/10/09 revision of the XScale ABI has wCG0
> @@ -30878,6 +30883,9 @@ arm_valid_target_attribute_rec (tree args, struct
>        else if (!strcmp (q, "arm"))
>         opts->x_target_flags &= ~MASK_THUMB;
>
> +      else if (!strcmp (q, "general-regs-only"))
> +       opts->x_target_flags |= MASK_GENERAL_REGS_ONLY;
> +
>        else if (!strncmp (q, "fpu=", 4))
>         {
>           int fpu_index;
> --- gcc/config/arm/arm.h        (revision 270444)
> +++ gcc/config/arm/arm.h        (working copy)
> @@ -122,12 +122,18 @@ extern tree arm_fp16_type_node;
>  #define TARGET_32BIT_P(flags)  (TARGET_ARM_P (flags) || TARGET_THUMB2_P (flags))
>
>  /* Run-time Target Specification.  */
> -/* Use hardware floating point instructions. */
> -#define TARGET_HARD_FLOAT      (arm_float_abi != ARM_FLOAT_ABI_SOFT    \
> +/* Use hardware floating point instructions. -mgeneral-regs-only prevents
> +the use of floating point instructions and registers but does not prevent
> +emission of floating point pcs attributes.  */
> +#define TARGET_HARD_FLOAT_SUB  (arm_float_abi != ARM_FLOAT_ABI_SOFT    \
>                                  && bitmap_bit_p (arm_active_target.isa, \
>                                                   isa_bit_vfpv2) \
>                                  && TARGET_32BIT)
> -#define TARGET_SOFT_FLOAT      (!TARGET_HARD_FLOAT)
> +
> +#define TARGET_HARD_FLOAT      (TARGET_HARD_FLOAT_SUB          \
> +                                && !TARGET_GENERAL_REGS_ONLY)
> +
> +#define TARGET_SOFT_FLOAT      (!TARGET_HARD_FLOAT_SUB)
>  /* User has permitted use of FP instructions, if they exist for this
>     target.  */
>  #define TARGET_MAYBE_HARD_FLOAT (arm_float_abi != ARM_FLOAT_ABI_SOFT)
> @@ -135,8 +141,10 @@ extern tree arm_fp16_type_node;
>  #define TARGET_HARD_FLOAT_ABI          (arm_float_abi == ARM_FLOAT_ABI_HARD)
>  #define TARGET_IWMMXT                  (arm_arch_iwmmxt)
>  #define TARGET_IWMMXT2                 (arm_arch_iwmmxt2)
> -#define TARGET_REALLY_IWMMXT           (TARGET_IWMMXT && TARGET_32BIT)
> -#define TARGET_REALLY_IWMMXT2          (TARGET_IWMMXT2 && TARGET_32BIT)
> +#define TARGET_REALLY_IWMMXT           (TARGET_IWMMXT && TARGET_32BIT \
> +                                        && !TARGET_GENERAL_REGS_ONLY)
> +#define TARGET_REALLY_IWMMXT2          (TARGET_IWMMXT2 && TARGET_32BIT \
> +                                        && !TARGET_GENERAL_REGS_ONLY)
>  #define TARGET_IWMMXT_ABI (TARGET_32BIT && arm_abi == ARM_ABI_IWMMXT)
>  #define TARGET_ARM                      (! TARGET_THUMB)
>  #define TARGET_EITHER                  1 /* (TARGET_ARM | TARGET_THUMB) */
> --- gcc/config/arm/arm.opt      (revision 270444)
> +++ gcc/config/arm/arm.opt      (working copy)
> @@ -302,3 +302,7 @@ When linking for big-endian targets, generate a le
>  mbranch-cost=
>  Target RejectNegative Joined UInteger Var(arm_branch_cost) Init(-1)
>  Cost to assume for a branch insn.
> +
> +mgeneral-regs-only
> +Target Report RejectNegative Mask(GENERAL_REGS_ONLY) Save
> +Generate code which uses the core registers only (r0-r14).
> --- gcc/doc/extend.texi (revision 270444)
> +++ gcc/doc/extend.texi (working copy)
> @@ -4190,6 +4190,15 @@ into the @code{sjli} table needs to be passed as a
>  These function attributes are supported for ARM targets:
>
>  @table @code
> +
> +@item general-regs-only
> +@cindex @code{general-regs-only} function attribute, ARM
> +Indicates that no floating-point or Advanced SIMD registers should be
> +used when generating code for this function.  If the function explicitly
> +uses floating-point code, then the compiler gives an error.  This is
> +the same behavior as that of the command-line option
> +@option{-mgeneral-regs-only}.
> +
>  @item interrupt
>  @cindex @code{interrupt} function attribute, ARM
>  Use this attribute to indicate
> --- gcc/doc/invoke.texi (revision 270444)
> +++ gcc/doc/invoke.texi (working copy)
> @@ -674,6 +674,7 @@ Objective-C and Objective-C++ Dialects}.
>  -mabi=@var{name} @gol
>  -mapcs-stack-check  -mno-apcs-stack-check @gol
>  -mapcs-reentrant  -mno-apcs-reentrant @gol
> +-mgeneral-regs-only @gol
>  -msched-prolog  -mno-sched-prolog @gol
>  -mlittle-endian  -mbig-endian @gol
>  -mbe8  -mbe32 @gol
> @@ -17068,6 +17069,12 @@ the hard-float and soft-float ABIs are not link-co
>  compile your entire program with the same ABI, and link with a
>  compatible set of libraries.
>
> +@item -mgeneral-regs-only
> +@opindex mgeneral-regs-only
> +Generate code which uses only the general-purpose registers.  This will prevent
> +the compiler from using floating-point and Advanced SIMD registers but will not
> +impose any restrictions on the assembler.
> +
>  @item -mlittle-endian
>  @opindex mlittle-endian
>  Generate code for a processor running in little-endian mode.  This is
> --- gcc/ada/raise-gcc.c (revision 270444)
> +++ gcc/ada/raise-gcc.c (working copy)
> @@ -1154,10 +1154,18 @@ extern void __gnat_notify_unhandled_exce
>  #define PERSONALITY_FUNCTION    __gnat_personality_v0
>  #endif
>
> +#if defined (__ARM_EABI_UNWINDER__) \
> +    && (defined (IN_RTS) || GCC_VERSION > 9000)
> +#define TARGET_ATTRIBUTE __attribute__((target ("general-regs-only")))
> +#else
> +#define TARGET_ATTRIBUTE
> +#endif
> +
>  /* Code executed to continue unwinding.  With the ARM unwinder, the
>     personality routine must unwind one frame (per EHABI 7.3 4.).  */
>
>  static _Unwind_Reason_Code
> +TARGET_ATTRIBUTE
>  continue_unwind (struct _Unwind_Exception* ue_header ATTRIBUTE_UNUSED,
>                  struct _Unwind_Context* uw_context ATTRIBUTE_UNUSED)
>  {
> @@ -1172,6 +1180,7 @@ continue_unwind (struct _Unwind_Exceptio
>     between all unwinders.  */
>
>  static _Unwind_Reason_Code
> +TARGET_ATTRIBUTE
>  personality_body (_Unwind_Action uw_phases,
>                   _Unwind_Exception *uw_exception,
>                   _Unwind_Context *uw_context)
> @@ -1342,6 +1351,7 @@ PERSONALITY_FUNCTION (_Unwind_State stat
>                       struct _Unwind_Context* uw_context);
>
>  PERSONALITY_STORAGE _Unwind_Reason_Code
> +TARGET_ATTRIBUTE
>  PERSONALITY_FUNCTION (_Unwind_State state,
>                       struct _Unwind_Exception* uw_exception,
>                       struct _Unwind_Context* uw_context)
> --- libgcc/config/arm/pr-support.c      (revision 270444)
> +++ libgcc/config/arm/pr-support.c      (working copy)
> @@ -21,6 +21,7 @@
>     see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
>     <http://www.gnu.org/licenses/>.  */
>
> +#pragma GCC target ("general-regs-only")
>  #include "unwind.h"
>
>  /* We add a prototype for abort here to avoid creating a dependency on
> --- libgcc/config/arm/unwind-arm.c      (revision 270444)
> +++ libgcc/config/arm/unwind-arm.c      (working copy)
> @@ -21,6 +21,7 @@
>     see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
>     <http://www.gnu.org/licenses/>.  */
>
> +#pragma GCC target ("general-regs-only")
>  #include "unwind.h"
>
>  /* Misc constants.  */
> --- libgcc/unwind-c.c   (revision 270444)
> +++ libgcc/unwind-c.c   (working copy)
> @@ -106,6 +106,7 @@ PERSONALITY_FUNCTION (_Unwind_State, struct _Unwin
>                       struct _Unwind_Context *);
>
>  _Unwind_Reason_Code
> +__attribute__((target ("general-regs-only")))
>  PERSONALITY_FUNCTION (_Unwind_State state,
>                       struct _Unwind_Exception * ue_header,
>                       struct _Unwind_Context * context)
> --- libgo/runtime/go-unwind.c   (revision 270444)
> +++ libgo/runtime/go-unwind.c   (working copy)
> @@ -411,7 +411,7 @@ parse_lsda_header (struct _Unwind_Contex
>  _Unwind_Reason_Code
>  PERSONALITY_FUNCTION (_Unwind_State, struct _Unwind_Exception *,
>                       struct _Unwind_Context *)
> -  __attribute__ ((no_split_stack, flatten));
> +  __attribute__ ((no_split_stack, flatten, target ("general-regs-only")));
>
>  _Unwind_Reason_Code
>  PERSONALITY_FUNCTION (_Unwind_State state,
> @@ -604,6 +604,9 @@ __gccgo_personality_dummy (int, _Unwind_
>    __attribute__ ((no_split_stack));
>
>  _Unwind_Reason_Code
> +#ifdef __ARM_EABI_UNWINDER__
> +__attribute__ ((target ("general-regs-only")))
> +#endif
>  __gccgo_personality_dummy (int version __attribute__ ((unused)),
>                       _Unwind_Action actions __attribute__ ((unused)),
>                       _Unwind_Exception_Class exception_class __attribute__ ((unused)),
> --- libobjc/exception.c (revision 270444)
> +++ libobjc/exception.c (working copy)
> @@ -220,6 +220,7 @@ get_ttype_entry (struct lsda_header_info *info, _U
>    while (0)
>
>  _Unwind_Reason_Code
> +__attribute__((target ("general-regs-only")))
>  PERSONALITY_FUNCTION (_Unwind_State state,
>                       struct _Unwind_Exception *ue_header,
>                       struct _Unwind_Context *context)
> --- libphobos/libdruntime/gcc/deh.d     (revision 270444)
> +++ libphobos/libdruntime/gcc/deh.d     (working copy)
> @@ -28,6 +28,7 @@ import gcc.unwind;
>  import gcc.unwind.pe;
>  import gcc.builtins;
>  import gcc.config;
> +import gcc.attribute;
>
>  extern(C)
>  {
> @@ -519,10 +520,19 @@ extern(C) void _d_throw(Throwable object)
>      terminate("unwind error", __LINE__);
>  }
>
> +static if (GNU_ARM_EABI_Unwinder)
> +{
> +    enum personality_fn_attributes = attribute("target", ("general-regs-only"));
> +}
> +else
> +{
> +    enum personality_fn_attributes = "";
> +}
>
>  /**
>   * Read and extract information from the LSDA (.gcc_except_table section).
>   */
> +@personality_fn_attributes
>  _Unwind_Reason_Code scanLSDA(const(ubyte)* lsda, _Unwind_Exception_Class exceptionClass,
>                               _Unwind_Action actions, _Unwind_Exception* unwindHeader,
>                               _Unwind_Context* context, _Unwind_Word cfa,
> @@ -772,6 +782,7 @@ int actionTableLookup(_Unwind_Action actions, _Unw
>   * Called when the personality function has found neither a cleanup or handler.
>   * To support ARM EABI personality routines, that must also unwind the stack.
>   */
> +@personality_fn_attributes
>  _Unwind_Reason_Code CONTINUE_UNWINDING(_Unwind_Exception* unwindHeader, _Unwind_Context* context)
>  {
>      static if (GNU_ARM_EABI_Unwinder)
> @@ -814,6 +825,7 @@ else
>  static if (GNU_ARM_EABI_Unwinder)
>  {
>      pragma(mangle, PERSONALITY_FUNCTION)
> +    @personality_fn_attributes
>      extern(C) _Unwind_Reason_Code gdc_personality(_Unwind_State state,
>                                                    _Unwind_Exception* unwindHeader,
>                                                    _Unwind_Context* context)
> @@ -873,6 +885,7 @@ else
>      }
>  }
>
> +@personality_fn_attributes
>  private _Unwind_Reason_Code __gdc_personality(_Unwind_Action actions,
>                                                _Unwind_Exception_Class exceptionClass,
>                                                _Unwind_Exception* unwindHeader,
> --- libstdc++-v3/libsupc++/eh_personality.cc    (revision 270444)
> +++ libstdc++-v3/libsupc++/eh_personality.cc    (working copy)
> @@ -343,6 +343,7 @@ extern "C"
>  #endif
>  _Unwind_Reason_Code
>  #ifdef __ARM_EABI_UNWINDER__
> +__attribute__((target ("general-regs-only")))
>  PERSONALITY_FUNCTION (_Unwind_State state,
>                       struct _Unwind_Exception* ue_header,
>                       struct _Unwind_Context* context)
>
>         Jakub

Re: [PATCH] Fix ARM exception handling (PR target/89093)

[Jonathan Wakely]

On 22/04/19 11:14 +0200, Jakub Jelinek wrote:
>Hi!
>
>As detailed in the PR, unlike most other targets, on ARM EABI the floating
>point registers are saved lazily, when EH personality routine calls
>__gnu_unwind_frame (usually in the CONTINUE_UNWINDING macro).
>That means the unwinder itself and the personality routines (and whatever
>other functions those call in the path to CONTINUE_UNWINDING) must be
>compiled so that it doesn't use floating point registers.  Calling some
>function that saves those on entry and restores on exit is fine, but calling
>some function which saves those on entry and then calls __gnu_unwind_frame
>and then restores on exit is not fine.
>In 8.x and earlier we were just lucky that the RA when compiling those
>didn't decide to use any of those registers, but starting with the combiner
>hard register changes we are no longer so lucky.
>
>The following patch introduces -mgeneral-regs-only option and
>general-regs-only target attribute for ARM (similarly to how other targets
>like AArch64 and x86), changes the ARM unwinder to be compiled with that
>and changes the personality routines of all languages so that either just
>the personality routine, or whatever other routines called by personality
>routines that call directly or indirectly __gnu_unwind_frame to be compiled
>that way.
>
>Bootstrapped/regtested on armv7hl-linux-gnueabi (and x86_64-linux to make
>sure it compiles on other targets too).
>
>Ok for trunk?

The libsupc++ part is OK.

Re: [PATCH] Fix ARM exception handling (PR target/89093)

[Jakub Jelinek]

On Tue, Apr 23, 2019 at 09:17:50AM +0100, Ramana Radhakrishnan wrote:
> > Ok for trunk?
> 
> Ok. Thanks a lot for working on this and fixing the rest of this up.
> I've been busy with a few other things.

Thanks.  Based on this and Iain and Jonathan's acks, I've committed
the patch except for the 

> > 2019-04-22  Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>
> >             Bernd Edlinger  <bernd.edlinger@hotmail.de>
> >             Jakub Jelinek  <jakub@redhat.com>
> >
> >         PR target/89093
> > gcc/ada/
> >         * raise-gcc.c (TARGET_ATTRIBUTE): Define.
> >         (continue_unwind, personality_body, PERSONALITY_FUNCTION): Add
> >         TARGET_ATTRIBUTE.
> > libgo/
> >         * runtime/go-unwind.c (PERSONALITY_FUNCTION,
> >         __gccgo_personality_dummy): Add general-regs-only target
> >         attribute for ARM.

parts, where for gcc/ada/ I'm waiting for an Ada maintainer review (CCed all
maintainers now) and for libgo I think this needs to be fixed upstream and
also dealt with non-gcc compilers or gcc 8.x and earlier.

	Jakub

Re: [PATCH] Fix ARM exception handling (PR target/89093)

[Eric Botcazou]

> The Ada changes need those guards because the file is compiled by both
> the system compiler and by the newly built compilers; when compiled by
> system compiler, as the FE is built with -fno-exceptions I'd hope the EH
> stuff isn't really used there and at least until GCC 9.1 is released we have
> the issue that the system compiler could be some earlier GCC 9.0.1 snapshot
> which doesn't support general-regs-only.

The Ada front-end does use EH on the host, but only the part written in Ada, 
that's why -fno-exceptions is very likely still OK for the C++ part.

The Ada bits are OK and I guess we don't care about earlier 9.0.1 snapshots.

-- 
Eric Botcazou

Re: [PATCH] Fix ARM exception handling (PR target/89093)

[Ian Lance Taylor]

On Mon, Apr 22, 2019 at 2:14 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> As detailed in the PR, unlike most other targets, on ARM EABI the floating
> point registers are saved lazily, when EH personality routine calls
> __gnu_unwind_frame (usually in the CONTINUE_UNWINDING macro).
> That means the unwinder itself and the personality routines (and whatever
> other functions those call in the path to CONTINUE_UNWINDING) must be
> compiled so that it doesn't use floating point registers.  Calling some
> function that saves those on entry and restores on exit is fine, but calling
> some function which saves those on entry and then calls __gnu_unwind_frame
> and then restores on exit is not fine.
> In 8.x and earlier we were just lucky that the RA when compiling those
> didn't decide to use any of those registers, but starting with the combiner
> hard register changes we are no longer so lucky.
>
> The following patch introduces -mgeneral-regs-only option and
> general-regs-only target attribute for ARM (similarly to how other targets
> like AArch64 and x86), changes the ARM unwinder to be compiled with that
> and changes the personality routines of all languages so that either just
> the personality routine, or whatever other routines called by personality
> routines that call directly or indirectly __gnu_unwind_frame to be compiled
> that way.
>
> Bootstrapped/regtested on armv7hl-linux-gnueabi (and x86_64-linux to make
> sure it compiles on other targets too).
>
> Ok for trunk?
>
> While the libgo changes are included in the patch, I think those need to go
> through go upstream and will likely need some changes if that code can be
> compiled by earlier GCC versions or other compilers.

Thanks.  I've committed the libgo changes.  (Older versions of GCC
have their own copy of libgo, and there are not yet any non-GCC
compilers that use this code and support ARM.)

Ian