[PATCH][AArch64] Don't allow -mgeneral-regs-only to change the .arch assembler directives

[PATCH][AArch64] Don't allow -mgeneral-regs-only to change the .arch assembler directives

[Kyrill Tkachov]

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Hi all,

As part of the SWITCHABLE_TARGET work I inadvertently changed the behaviour of -mgeneral-regs-only with respect to the .arch directives that we emit.
The behaviour of -mgeneral-regs-only in GCC 5 and earlier is such that it disallows the usage of FP/SIMD registers but does *not* stop the compiler from
emitting the +fp,+simd etc extensions in the .arch directive of the generated assembly. This is to accommodate users who may want to write inline assembly
in a file compiled with -mgeneral-regs-only.

This patch restores the trunk behaviour in that respect to that of GCC 5 and the documentation for the option is tweaked a bit to reflect that.
Bootstrapped and tested on aarch64.

Ok for trunk?

Thanks,
Kyrill

2015-10-01  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

     * config/aarch64/aarch64.c (aarch64_override_options_internal):
     Do not alter target_flags due to TARGET_GENERAL_REGS_ONLY_P.
     * doc/invoke.texi (AArch64 options): Mention that -mgeneral-regs-only
     does not affect the assembler directives.

2015-10-01  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

     * gcc.target/aarch64/mgeneral-regs_4.c: New test.

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commit bd99347f0dad9346dc16ffc13cd423a4889ae339
Author: Kyrylo Tkachov <kyrylo.tkachov@arm.com>
Date:   Fri Sep 11 09:40:44 2015 +0100

    [AArch64] Don't allow -mgeneral-regs-only to change the .arch assembler directives

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 115c3a7..81e0eb0 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -7658,19 +7658,6 @@ aarch64_override_options_internal (struct gcc_options *opts)
   if (opts->x_flag_strict_volatile_bitfields < 0 && abi_version_at_least (2))
     opts->x_flag_strict_volatile_bitfields = 1;
 
-  /* -mgeneral-regs-only sets a mask in target_flags, make sure that
-     aarch64_isa_flags does not contain the FP/SIMD/Crypto feature flags
-     in case some code tries reading aarch64_isa_flags directly to check if
-     FP is available.  Reuse the aarch64_parse_extension machinery since it
-     knows how to disable any other flags that fp implies.  */
-  if (TARGET_GENERAL_REGS_ONLY_P (opts->x_target_flags))
-    {
-      /* aarch64_parse_extension takes char* rather than const char* because
-	 it is usually called from within other parsing functions.  */
-      char tmp_str[] = "+nofp";
-      aarch64_parse_extension (tmp_str, &opts->x_aarch64_isa_flags);
-    }
-
   initialize_aarch64_code_model (opts);
   initialize_aarch64_tls_size (opts);
 
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 547ee2d..e8067f2 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -12304,10 +12304,9 @@ Generate big-endian code.  This is the default when GCC is configured for an
 
 @item -mgeneral-regs-only
 @opindex mgeneral-regs-only
-Generate code which uses only the general-purpose registers.  This is equivalent
-to feature modifier @option{nofp} of @option{-march} or @option{-mcpu}, except
-that @option{-mgeneral-regs-only} takes precedence over any conflicting feature
-modifier regardless of sequence.
+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
diff --git a/gcc/testsuite/gcc.target/aarch64/mgeneral-regs_4.c b/gcc/testsuite/gcc.target/aarch64/mgeneral-regs_4.c
new file mode 100644
index 0000000..8eb50aa
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/mgeneral-regs_4.c
@@ -0,0 +1,9 @@
+/* { dg-options "-mgeneral-regs-only -march=armv8-a+simd+fp -O2" } */
+
+int
+test (void)
+{
+  return 1;
+}
+
+/* { dg-final { scan-assembler "\.arch.*fp.*simd" } } */

Re: [PATCH][AArch64] Don't allow -mgeneral-regs-only to change the .arch assembler directives

[Kyrill Tkachov]

Ping.
This almost fell through the cracks.
https://gcc.gnu.org/ml/gcc-patches/2015-10/msg00055.html

Thanks,
Kyrill

On 01/10/15 14:00, Kyrill Tkachov wrote:
> Hi all,
>
> As part of the SWITCHABLE_TARGET work I inadvertently changed the behaviour of -mgeneral-regs-only with respect to the .arch directives that we emit.
> The behaviour of -mgeneral-regs-only in GCC 5 and earlier is such that it disallows the usage of FP/SIMD registers but does *not* stop the compiler from
> emitting the +fp,+simd etc extensions in the .arch directive of the generated assembly. This is to accommodate users who may want to write inline assembly
> in a file compiled with -mgeneral-regs-only.
>
> This patch restores the trunk behaviour in that respect to that of GCC 5 and the documentation for the option is tweaked a bit to reflect that.
> Bootstrapped and tested on aarch64.
>
> Ok for trunk?
>
> Thanks,
> Kyrill
>
> 2015-10-01  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>
>       * config/aarch64/aarch64.c (aarch64_override_options_internal):
>       Do not alter target_flags due to TARGET_GENERAL_REGS_ONLY_P.
>       * doc/invoke.texi (AArch64 options): Mention that -mgeneral-regs-only
>       does not affect the assembler directives.
>
> 2015-10-01  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>
>       * gcc.target/aarch64/mgeneral-regs_4.c: New test.

Re: [PATCH][AArch64] Don't allow -mgeneral-regs-only to change the .arch assembler directives

[Marcus Shawcroft]

On 04/12/15 14:40, Kyrill Tkachov wrote:
> Ping.
> This almost fell through the cracks.
> https://gcc.gnu.org/ml/gcc-patches/2015-10/msg00055.html
>
> Thanks,
> Kyrill
>
> On 01/10/15 14:00, Kyrill Tkachov wrote:
>> Hi all,
>>
>> As part of the SWITCHABLE_TARGET work I inadvertently changed the
>> behaviour of -mgeneral-regs-only with respect to the .arch directives
>> that we emit.
>> The behaviour of -mgeneral-regs-only in GCC 5 and earlier is such that
>> it disallows the usage of FP/SIMD registers but does *not* stop the
>> compiler from
>> emitting the +fp,+simd etc extensions in the .arch directive of the
>> generated assembly. This is to accommodate users who may want to write
>> inline assembly
>> in a file compiled with -mgeneral-regs-only.
>>
>> This patch restores the trunk behaviour in that respect to that of GCC
>> 5 and the documentation for the option is tweaked a bit to reflect that.
>> Bootstrapped and tested on aarch64.
>>
>> Ok for trunk?
>>
>> Thanks,
>> Kyrill
>>
>> 2015-10-01  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>>
>>       * config/aarch64/aarch64.c (aarch64_override_options_internal):
>>       Do not alter target_flags due to TARGET_GENERAL_REGS_ONLY_P.
>>       * doc/invoke.texi (AArch64 options): Mention that
>> -mgeneral-regs-only
>>       does not affect the assembler directives.
>>
>> 2015-10-01  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>>
>>       * gcc.target/aarch64/mgeneral-regs_4.c: New test.
>

OK /M