Re: [PATCH, ARM] Do softfloat when -mfpu set, -mfloat-abi=softfp and targeting Thumb-1

[Thomas Preudhomme <thomas.preudhomme@linaro.org>]

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Good catch.

Committed patch in attachment. Best regards,

Thomas
On Wed, 19 Dec 2018 at 14:13, Richard Earnshaw (lists)
<Richard.Earnshaw@arm.com> wrote:
>
> On 14/12/2018 21:15, Thomas Preudhomme wrote:
> > Hi Richard,
> >
> > Thanks for catching the problem with this approach. Hopefully this
> > version should solve the real problem:
> >
> >
> > FP instructions are only enabled for TARGET_32BIT and TARGET_HARD_FLOAT
> > but GCC only gives an error when TARGET_HARD_FLOAT is true and -mfpu is
> > not set. Among other things, it makes some of the cmse tests (eg.
> > gcc.target/arm/cmse/baseline/softfp.c) fail when targeting
> > -march=armv8-m.base -mcmse -mfpu=<something> -mfloat-abi=softfp. This
> > patch adds an extra check for TARGET_32BIT to TARGET_HARD_FLOAT such
> > that it is false on TARGET_THUMB1 targets even when a FPU is specified.
> >
> > ChangeLog entries are as follows:
> >
> > *** gcc/ChangeLog ***
> >
> > 2018-12-14  thomas Preud'homme  <thomas.preudhomme@linaro.org>
> >
> >         * config/arm/arm.h (TARGET_HARD_FLOAT): Restrict to TARGET_32BIT
> >         targets.
>
> Yes, this is better.  And with this change, I think this line:
>
>               if (TARGET_HARD_FLOAT && !TARGET_THUMB1)
>
> in output_return_instruction() can be collapsed into simply
>
>
>         if (TARGET_HARD_FLOAT)
>
> OK with that change.
>
> R.
>
> >
> > *** gcc/testsuite/ChangeLog ***
> >
> > 2018-12-14  thomas Preud'homme  <thomas.preudhomme@linaro.org>
> >
> >         * gcc.target/arm/cmse/baseline/softfp.c: Force an FPU.
> >
> > Testing: No testsuite regression when targeting arm-none-eabi Armv6S-M
> > with -mfloat-abi=softfp
> >
> > Is this ok for stage3?
> >
> > Best regards,
> >
> > Thomas
> >
> > On Thu, 29 Nov 2018 at 14:52, Richard Earnshaw (lists)
> > <Richard.Earnshaw@arm.com> wrote:
> >>
> >> On 29/11/2018 10:51, Thomas Preudhomme wrote:
> >>> Hi,
> >>>
> >>> FP instructions are only enabled for TARGET_32BIT and TARGET_HARD_FLOAT
> >>> but GCC only gives an error when TARGET_HARD_FLOAT is true and -mfpu is
> >>> not set. Among other things, it makes some of the cmse tests (eg.
> >>> gcc.target/arm/cmse/baseline/softfp.c) fail when targeting
> >>> -march=armv8-m.base -mfpu=<something> -mfloat-abi=softfp. This patch
> >>> errors out when a Thumb-1 -like target is selected and a FPU is
> >>> specified, thus making such tests being skipped.
> >>>
> >>> ChangeLog entries are as follows:
> >>>
> >>> *** gcc/ChangeLog ***
> >>>
> >>> 2018-11-28  thomas Preud'homme  <thomas.preudhomme@linaro.org>
> >>>
> >>>     * config/arm/arm.c (arm_options_perform_arch_sanity_checks): Error out
> >>>     if targeting Thumb-1 with an FPU specified.
> >>>
> >>> *** gcc/testsuite/ChangeLog ***
> >>>
> >>> 2018-11-28  thomas Preud'homme  <thomas.preudhomme@linaro.org>
> >>>
> >>>     * gcc.target/arm/thumb1_mfpu-1.c: New testcase.
> >>>     * gcc.target/arm/thumb1_mfpu-2.c: Likewise.
> >>>
> >>> Testing: No testsuite regression when targeting arm-none-eabi Armv6S-M.
> >>> Fails as expected when targeting Armv6-M with an -mfpu or a default FPU.
> >>> Succeeds without.
> >>>
> >>> Is this ok for stage3?
> >>>
> >>
> >> This doesn't sound right.  Specifically this bit...
> >>
> >> +      else if (TARGET_THUMB1
> >> +              && bitmap_bit_p (arm_active_target.isa, isa_bit_vfpv2))
> >> +       error ("Thumb-1 does not allow FP instructions");
> >>
> >> If I use
> >>
> >>     -mcpu=arm1176jzf-s -mfpu=auto -mfloat-abi=softfp -mthumb
> >>
> >> then that shouldn't error, since softfp and thumb is, in reality, just
> >> float-abi=soft (as there are no fp instructions in thumb).  We also want
> >> it to work this way so that I can add the thumb/arm attribute to
> >> specific functions and have the compiler use HW float instructions when
> >> they are suitable.
> >>
> >>
> >> R.
> >>
> >>> Best regards,
> >>>
> >>> Thomas
> >>>
> >>>
> >>> thumb1_mfpu_error.patch
> >>>
> >>> From 051e38552d7c596873e0303f6ec4272b26d50900 Mon Sep 17 00:00:00 2001
> >>> From: Thomas Preud'homme <thomas.preudhomme@linaro.org>
> >>> Date: Tue, 27 Nov 2018 15:52:38 +0000
> >>> Subject: [PATCH] [PATCH, ARM] Error out when -mfpu set and targeting Thumb-1
> >>>
> >>> Hi,
> >>>
> >>> FP instructions are only enabled for TARGET_32BIT and TARGET_HARD_FLOAT
> >>> but GCC only gives an error when TARGET_HARD_FLOAT is true and -mfpu is
> >>> not set. Among other things, it makes some of the cmse tests (eg.
> >>> gcc.target/arm/cmse/baseline/softfp.c) fail when targeting
> >>> -march=armv8-m.base -mfpu=<something> -mfloat-abi=softfp. This patch
> >>> errors out when a Thumb-1 -like target is selected and a FPU is
> >>> specified, thus making such tests being skipped.
> >>>
> >>> ChangeLog entries are as follows:
> >>>
> >>> *** gcc/ChangeLog ***
> >>>
> >>> 2018-11-28  thomas Preud'homme  <thomas.preudhomme@linaro.org>
> >>>
> >>>       * config/arm/arm.c (arm_options_perform_arch_sanity_checks): Error out
> >>>       if targeting Thumb-1 with an FPU specified.
> >>>
> >>> *** gcc/testsuite/ChangeLog ***
> >>>
> >>> 2018-11-28  thomas Preud'homme  <thomas.preudhomme@linaro.org>
> >>>
> >>>       * gcc.target/arm/thumb1_mfpu-1.c: New testcase.
> >>>       * gcc.target/arm/thumb1_mfpu-2.c: Likewise.
> >>>
> >>> Testing: No testsuite regression when targeting arm-none-eabi Armv6S-M.
> >>> Fails as expected when targeting Armv6-M with an -mfpu or a default FPU.
> >>> Succeeds without.
> >>>
> >>> Is this ok for stage3?
> >>>
> >>> Best regards,
> >>>
> >>> Thomas
> >>> ---
> >>>  gcc/config/arm/arm.c                         | 3 +++
> >>>  gcc/testsuite/gcc.target/arm/thumb1_mfpu-1.c | 7 +++++++
> >>>  gcc/testsuite/gcc.target/arm/thumb1_mfpu-2.c | 8 ++++++++
> >>>  3 files changed, 18 insertions(+)
> >>>  create mode 100644 gcc/testsuite/gcc.target/arm/thumb1_mfpu-1.c
> >>>  create mode 100644 gcc/testsuite/gcc.target/arm/thumb1_mfpu-2.c
> >>>
> >>> diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
> >>> index 40f0574e32e..1a205123cf5 100644
> >>> --- a/gcc/config/arm/arm.c
> >>> +++ b/gcc/config/arm/arm.c
> >>> @@ -3747,6 +3747,9 @@ arm_options_perform_arch_sanity_checks (void)
> >>>      {
> >>>        if (arm_abi == ARM_ABI_IWMMXT)
> >>>       arm_pcs_default = ARM_PCS_AAPCS_IWMMXT;
> >>> +      else if (TARGET_THUMB1
> >>> +            && bitmap_bit_p (arm_active_target.isa, isa_bit_vfpv2))
> >>> +     error ("Thumb-1 does not allow FP instructions");
> >>>        else if (TARGET_HARD_FLOAT_ABI)
> >>>       {
> >>>         arm_pcs_default = ARM_PCS_AAPCS_VFP;
> >>> diff --git a/gcc/testsuite/gcc.target/arm/thumb1_mfpu-1.c b/gcc/testsuite/gcc.target/arm/thumb1_mfpu-1.c
> >>> new file mode 100644
> >>> index 00000000000..5347e63f9b6
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/gcc.target/arm/thumb1_mfpu-1.c
> >>> @@ -0,0 +1,7 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-require-effective-target arm_thumb1_ok } */
> >>> +/* { dg-skip-if "incompatible float ABI" { *-*-* } { "-mfloat-abi=*" } { "-mfloat-abi=softfp" } } */
> >>> +/* { dg-options "-mthumb -mfpu=vfp -mfloat-abi=softfp" } */
> >>> +/* { dg-error "Thumb-1 does not allow FP instructions" "" { target *-*-* } 0 } */
> >>> +
> >>> +int foo;
> >>> diff --git a/gcc/testsuite/gcc.target/arm/thumb1_mfpu-2.c b/gcc/testsuite/gcc.target/arm/thumb1_mfpu-2.c
> >>> new file mode 100644
> >>> index 00000000000..941ed26ed01
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/gcc.target/arm/thumb1_mfpu-2.c
> >>> @@ -0,0 +1,8 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-require-effective-target arm_thumb1_ok } */
> >>> +/* { dg-skip-if "incompatible float ABI" { *-*-* } { "-mfloat-abi=*" } { "-mfloat-abi=softfp" } } */
> >>> +/* No need to skip in presence of -mfpu since arm_thumb1_ok will already fail
> >>> +   due to Thumb-1 with -mfpu which is tested by thumb1_mfpu-1 testcase.  */
> >>> +/* { dg-options "-mthumb -mfloat-abi=softfp" } */
> >>> +
> >>> +int foo;
> >>>
> >>
> >>
> >> softfloat_mfpu_set_softfp_thumb1.patch
> >>
> >> From 7c056f386df458f08c0ae367edc7050d53cd6602 Mon Sep 17 00:00:00 2001
> >> From: Thomas Preud'homme <thomas.preudhomme@linaro.org>
> >> Date: Tue, 27 Nov 2018 15:52:38 +0000
> >> Subject: [PATCH] [PATCH, ARM] Do softfloat when -mfpu set, -mfloat-abi=softfp
> >>  and targeting Thumb-1
> >>
> >> Hi,
> >>
> >> FP instructions are only enabled for TARGET_32BIT and TARGET_HARD_FLOAT
> >> but GCC only gives an error when TARGET_HARD_FLOAT is true and -mfpu is
> >> not set. Among other things, it makes some of the cmse tests (eg.
> >> gcc.target/arm/cmse/baseline/softfp.c) fail when targeting
> >> -march=armv8-m.base -mcmse -mfpu=<something> -mfloat-abi=softfp. This
> >> patch adds an extra check for TARGET_32BIT to TARGET_HARD_FLOAT such
> >> that it is false on TARGET_THUMB1 targets even when a FPU is specified.
> >>
> >> ChangeLog entries are as follows:
> >>
> >> *** gcc/ChangeLog ***
> >>
> >> 2018-12-14  thomas Preud'homme  <thomas.preudhomme@linaro.org>
> >>
> >>      * config/arm/arm.h (TARGET_HARD_FLOAT): Restrict to TARGET_32BIT
> >>      targets.
> >>
> >> *** gcc/testsuite/ChangeLog ***
> >>
> >> 2018-12-14  thomas Preud'homme  <thomas.preudhomme@linaro.org>
> >>
> >>      * gcc.target/arm/cmse/baseline/softfp.c: Force an FPU.
> >>
> >> Testing: No testsuite regression when targeting arm-none-eabi Armv6S-M.
> >>
> >> Is this ok for stage3?
> >>
> >> Best regards,
> >>
> >> Thomas
> >> ---
> >>  gcc/config/arm/arm.h                                | 3 ++-
> >>  gcc/testsuite/gcc.target/arm/cmse/baseline/softfp.c | 4 +++-
> >>  2 files changed, 5 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/gcc/config/arm/arm.h b/gcc/config/arm/arm.h
> >> index 8472312487b..149243d0978 100644
> >> --- a/gcc/config/arm/arm.h
> >> +++ b/gcc/config/arm/arm.h
> >> @@ -125,7 +125,8 @@ extern tree arm_fp16_type_node;
> >>  /* Use hardware floating point instructions. */
> >>  #define TARGET_HARD_FLOAT   (arm_float_abi != ARM_FLOAT_ABI_SOFT    \
> >>                               && bitmap_bit_p (arm_active_target.isa, \
> >> -                                              isa_bit_vfpv2))
> >> +                                              isa_bit_vfpv2) \
> >> +                             && TARGET_32BIT)
> >>  #define TARGET_SOFT_FLOAT   (!TARGET_HARD_FLOAT)
> >>  /* User has permitted use of FP instructions, if they exist for this
> >>     target.  */
> >> diff --git a/gcc/testsuite/gcc.target/arm/cmse/baseline/softfp.c b/gcc/testsuite/gcc.target/arm/cmse/baseline/softfp.c
> >> index 3d383ff6ee1..30b3eec078c 100644
> >> --- a/gcc/testsuite/gcc.target/arm/cmse/baseline/softfp.c
> >> +++ b/gcc/testsuite/gcc.target/arm/cmse/baseline/softfp.c
> >> @@ -1,5 +1,7 @@
> >>  /* { dg-do compile } */
> >> -/* { dg-options "-mcmse -mfloat-abi=softfp" } */
> >> +/* Force an FPU to test that it is ignored for Thumb-1 -like targets and that
> >> +   no clearing of VFP register occurs.  */
> >> +/* { dg-options "-mcmse -mfloat-abi=softfp -mfpu=fpv5-d16" } */
> >>
> >>  double __attribute__ ((cmse_nonsecure_call)) (*bar) (float, double);
> >>
>

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From ca495cecf39eabe761eb073dbbe844118a98229d Mon Sep 17 00:00:00 2001
From: Thomas Preud'homme <thomas.preudhomme@linaro.org>
Date: Tue, 27 Nov 2018 15:52:38 +0000
Subject: [PATCH] [PATCH, ARM] Do softfloat when -mfpu set, -mfloat-abi=softfp
 and targeting Thumb-1

Hi,

FP instructions are only enabled for TARGET_32BIT and TARGET_HARD_FLOAT
but GCC only gives an error when TARGET_HARD_FLOAT is true and -mfpu is
not set. Among other things, it makes some of the cmse tests (eg.
gcc.target/arm/cmse/baseline/softfp.c) fail when targeting
-march=armv8-m.base -mcmse -mfpu=<something> -mfloat-abi=softfp. This
patch adds an extra check for TARGET_32BIT to TARGET_HARD_FLOAT such
that it is false on TARGET_THUMB1 targets even when a FPU is specified.

ChangeLog entries are as follows:

*** gcc/ChangeLog ***

2018-12-19  thomas Preud'homme  <thomas.preudhomme@linaro.org>

	* config/arm/arm.h (TARGET_HARD_FLOAT): Restrict to TARGET_32BIT
	targets.
	* config/arm/arm.c (output_return_instruction): Only check
	TARGET_HARD_FLOAT to decide whether FP instructions are available.

*** gcc/testsuite/ChangeLog ***

2018-12-14  thomas Preud'homme  <thomas.preudhomme@linaro.org>

	* gcc.target/arm/cmse/baseline/softfp.c: Force an FPU.

Testing: No testsuite regression when targeting arm-none-eabi Armv6S-M.

Is this ok for stage3?

Best regards,

Thomas
---
 gcc/config/arm/arm.c                                | 2 +-
 gcc/config/arm/arm.h                                | 3 ++-
 gcc/testsuite/gcc.target/arm/cmse/baseline/softfp.c | 4 +++-
 3 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 40f0574e32e..509f287aa63 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -19872,7 +19872,7 @@ output_return_instruction (rtx operand, bool really_return, bool reverse,
 			  "msr%s\tAPSR_nzcvq, %%|lr", conditional);
 
 	      output_asm_insn (instr, & operand);
-	      if (TARGET_HARD_FLOAT && !TARGET_THUMB1)
+	      if (TARGET_HARD_FLOAT)
 		{
 		  /* Clear the cumulative exception-status bits (0-4,7) and the
 		     condition code bits (28-31) of the FPSCR.  We need to
diff --git a/gcc/config/arm/arm.h b/gcc/config/arm/arm.h
index 8472312487b..149243d0978 100644
--- a/gcc/config/arm/arm.h
+++ b/gcc/config/arm/arm.h
@@ -125,7 +125,8 @@ extern tree arm_fp16_type_node;
 /* Use hardware floating point instructions. */
 #define TARGET_HARD_FLOAT	(arm_float_abi != ARM_FLOAT_ABI_SOFT	\
 				 && bitmap_bit_p (arm_active_target.isa, \
-						  isa_bit_vfpv2))
+						  isa_bit_vfpv2) \
+				 && TARGET_32BIT)
 #define TARGET_SOFT_FLOAT	(!TARGET_HARD_FLOAT)
 /* User has permitted use of FP instructions, if they exist for this
    target.  */
diff --git a/gcc/testsuite/gcc.target/arm/cmse/baseline/softfp.c b/gcc/testsuite/gcc.target/arm/cmse/baseline/softfp.c
index 3d383ff6ee1..30b3eec078c 100644
--- a/gcc/testsuite/gcc.target/arm/cmse/baseline/softfp.c
+++ b/gcc/testsuite/gcc.target/arm/cmse/baseline/softfp.c
@@ -1,5 +1,7 @@
 /* { dg-do compile } */
-/* { dg-options "-mcmse -mfloat-abi=softfp" } */
+/* Force an FPU to test that it is ignored for Thumb-1 -like targets and that
+   no clearing of VFP register occurs.  */
+/* { dg-options "-mcmse -mfloat-abi=softfp -mfpu=fpv5-d16" } */
 
 double __attribute__ ((cmse_nonsecure_call)) (*bar) (float, double);
 
-- 
2.19.1