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* [Bug target/99773] New: ARM v8.1-m MVE interaction with -mfloat-abi not clear
@ 2021-03-25 16:26 clyon at gcc dot gnu.org
2021-03-25 16:49 ` [Bug target/99773] " rearnsha at gcc dot gnu.org
` (6 more replies)
0 siblings, 7 replies; 8+ messages in thread
From: clyon at gcc dot gnu.org @ 2021-03-25 16:26 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99773
Bug ID: 99773
Summary: ARM v8.1-m MVE interaction with -mfloat-abi not clear
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: clyon at gcc dot gnu.org
Target Milestone: ---
I noticed an unexpected linker error when compiling with
-march=armv8.1-m.main+mve -mfloat-abi=hard -mcpu=cortex-m55 -mthumb
error: /tmp/ccQvvmcJ.o uses VFP register arguments, ./XXX.exe does not
Using mve.fp instead of mve fixes that.
However, I'm used to -mfloat-abi=hard defining the eabi attribute:
Tag_ABI_VFP_args: VFP registers
Compiling
===================================
typedef int __attribute((vector_size(16))) v4si;
float g(float x, float y)
{
x += y;
return x;
}
v4si f(v4si x, v4si y)
{
return x + y;
}
===================================
with -O2 -march=armv8.1-m.main+mve -mfloat-abi=hard
generates for f:
vadd.i32 q0, q0, q1
bx lr
which uses the MVE registers for the parameters, but the object files does not
have the Tag_ABI_VFP_args: VFP registers attribute I would expect.
It does have
Tag_MVE_arch: MVE Integer only
is that enough?
Is the current behavior expected or is there a bug?
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug target/99773] ARM v8.1-m MVE interaction with -mfloat-abi not clear
2021-03-25 16:26 [Bug target/99773] New: ARM v8.1-m MVE interaction with -mfloat-abi not clear clyon at gcc dot gnu.org
@ 2021-03-25 16:49 ` rearnsha at gcc dot gnu.org
2021-03-25 16:58 ` acoplan at gcc dot gnu.org
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: rearnsha at gcc dot gnu.org @ 2021-03-25 16:49 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99773
--- Comment #1 from Richard Earnshaw <rearnsha at gcc dot gnu.org> ---
-march=armv8.1-m.main+mve -mfloat-abi=hard should use the VFP registers for
passing any FP arguments so the build attribute for Tag_ABI_VFP_args should be
set to show that.
It's true that soft-float routines will still be needed to do any FP operations
in this case, but that doesn't affect the ABI at public interfaces.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug target/99773] ARM v8.1-m MVE interaction with -mfloat-abi not clear
2021-03-25 16:26 [Bug target/99773] New: ARM v8.1-m MVE interaction with -mfloat-abi not clear clyon at gcc dot gnu.org
2021-03-25 16:49 ` [Bug target/99773] " rearnsha at gcc dot gnu.org
@ 2021-03-25 16:58 ` acoplan at gcc dot gnu.org
2021-03-25 17:57 ` clyon at gcc dot gnu.org
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: acoplan at gcc dot gnu.org @ 2021-03-25 16:58 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99773
Alex Coplan <acoplan at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2021-03-25
Ever confirmed|0 |1
--- Comment #2 from Alex Coplan <acoplan at gcc dot gnu.org> ---
Confirmed, then.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug target/99773] ARM v8.1-m MVE interaction with -mfloat-abi not clear
2021-03-25 16:26 [Bug target/99773] New: ARM v8.1-m MVE interaction with -mfloat-abi not clear clyon at gcc dot gnu.org
2021-03-25 16:49 ` [Bug target/99773] " rearnsha at gcc dot gnu.org
2021-03-25 16:58 ` acoplan at gcc dot gnu.org
@ 2021-03-25 17:57 ` clyon at gcc dot gnu.org
2021-03-26 11:23 ` rearnsha at gcc dot gnu.org
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: clyon at gcc dot gnu.org @ 2021-03-25 17:57 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99773
--- Comment #3 from Christophe Lyon <clyon at gcc dot gnu.org> ---
I tried changing TARGET_HARD_FLOAT_SUB in arm.h to:
#define TARGET_HARD_FLOAT_SUB (arm_float_abi != ARM_FLOAT_ABI_SOFT \
&& (bitmap_bit_p (arm_active_target.isa, \
isa_bit_vfpv2) \
|| bitmap_bit_p (arm_active_target.isa, \
isa_bit_mve)) \
&& TARGET_32BIT)
but that has other implications, like enabing VFP patterns: for instance
mulsf3_vfp becomes enabled, leading to a failure when builing libgcc (vmul.f32
is generated for powisf2, but rejected by the assembler)
So maybe we just change the condition to emit the attributes in arm_file_start?
Something like:
if (! TARGET_SOFT_FLOAT || TARGET_HAVE_MVE)
{
if ((TARGET_HARD_FLOAT && TARGET_VFP_SINGLE) || TARGET_HAVE_MVE)
arm_emit_eabi_attribute ("Tag_ABI_HardFP_use", 27, 1);
if (TARGET_HARD_FLOAT_ABI || TARGET_HAVE_MVE)
arm_emit_eabi_attribute ("Tag_ABI_VFP_args", 28, 1);
}
but that does not look very clean
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug target/99773] ARM v8.1-m MVE interaction with -mfloat-abi not clear
2021-03-25 16:26 [Bug target/99773] New: ARM v8.1-m MVE interaction with -mfloat-abi not clear clyon at gcc dot gnu.org
` (2 preceding siblings ...)
2021-03-25 17:57 ` clyon at gcc dot gnu.org
@ 2021-03-26 11:23 ` rearnsha at gcc dot gnu.org
2021-03-26 14:27 ` clyon at gcc dot gnu.org
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: rearnsha at gcc dot gnu.org @ 2021-03-26 11:23 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99773
--- Comment #4 from Richard Earnshaw <rearnsha at gcc dot gnu.org> ---
(In reply to Christophe Lyon from comment #3)
> I tried changing TARGET_HARD_FLOAT_SUB in arm.h to:
> #define TARGET_HARD_FLOAT_SUB (arm_float_abi != ARM_FLOAT_ABI_SOFT \
> && (bitmap_bit_p (arm_active_target.isa, \
> isa_bit_vfpv2) \
> || bitmap_bit_p (arm_active_target.isa, \
> isa_bit_mve)) \
> && TARGET_32BIT)
>
> but that has other implications, like enabing VFP patterns: for instance
> mulsf3_vfp becomes enabled, leading to a failure when builing libgcc
> (vmul.f32 is generated for powisf2, but rejected by the assembler)
>
> So maybe we just change the condition to emit the attributes in
> arm_file_start?
>
> Something like:
> if (! TARGET_SOFT_FLOAT || TARGET_HAVE_MVE)
> {
> if ((TARGET_HARD_FLOAT && TARGET_VFP_SINGLE) || TARGET_HAVE_MVE)
> arm_emit_eabi_attribute ("Tag_ABI_HardFP_use", 27, 1);
>
> if (TARGET_HARD_FLOAT_ABI || TARGET_HAVE_MVE)
> arm_emit_eabi_attribute ("Tag_ABI_VFP_args", 28, 1);
> }
>
It doesn't look right, either. Why would you want to set Tag_ABI_HardFP_use to
1 when there's no single-precision only FPU present?
Untested, but I think something like
if (TARGET_HARD_FLOAT && TARGET_VFP_SINGLE)
arm_emit_eabi_attribute ("Tag_ABI_HardFP_use", 27, 1);
if (TARGET_HARD_FLOAT_ABI)
arm_emit_eabi_attribute ("Tag_ABI_VFP_args", 28, 1);
is probably the right solution, removing the ! TARGET_SOFT_FLOAT entirely.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug target/99773] ARM v8.1-m MVE interaction with -mfloat-abi not clear
2021-03-25 16:26 [Bug target/99773] New: ARM v8.1-m MVE interaction with -mfloat-abi not clear clyon at gcc dot gnu.org
` (3 preceding siblings ...)
2021-03-26 11:23 ` rearnsha at gcc dot gnu.org
@ 2021-03-26 14:27 ` clyon at gcc dot gnu.org
2021-03-30 13:11 ` cvs-commit at gcc dot gnu.org
2021-03-30 13:12 ` clyon at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: clyon at gcc dot gnu.org @ 2021-03-26 14:27 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99773
--- Comment #5 from Christophe Lyon <clyon at gcc dot gnu.org> ---
Compiling with -march=armv8.1-m.main+mve -mfloat-abi=hard defines:
TARGET_SOFT_FLOAT 1
TARGET_HARD_FLOAT 0
TARGET_HARD_FLOAT_ABI 1
TARGET_VFP_SINGLE 1
so indeed what you propose does the trick.
(Sorry I proposed comment #3 yesterday too in a hurry)
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug target/99773] ARM v8.1-m MVE interaction with -mfloat-abi not clear
2021-03-25 16:26 [Bug target/99773] New: ARM v8.1-m MVE interaction with -mfloat-abi not clear clyon at gcc dot gnu.org
` (4 preceding siblings ...)
2021-03-26 14:27 ` clyon at gcc dot gnu.org
@ 2021-03-30 13:11 ` cvs-commit at gcc dot gnu.org
2021-03-30 13:12 ` clyon at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2021-03-30 13:11 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99773
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Christophe Lyon <clyon@gcc.gnu.org>:
https://gcc.gnu.org/g:6f93a7c7fc62b2d6ab47e5d5eb60d41366e1ee9e
commit r11-7908-g6f93a7c7fc62b2d6ab47e5d5eb60d41366e1ee9e
Author: Christophe Lyon <christophe.lyon@linaro.org>
Date: Tue Mar 30 12:26:33 2021 +0000
arm: Fix emission of Tag_ABI_VFP_args with MVE and -mfloat-abi=hard (PR
target/99773)
When compiling with -mfloat-abi=hard -march=armv8.1-m.main+mve, we
want to emit Tag_ABI_VFP_args even though we are not emitting
floating-point instructions (we need "+mve.fp" for that), because we
use MVE registers to pass FP arguments.
This patch removes the condition on (! TARGET_SOFT_FLOAT) because this
is a case where TARGET_SOFT_FLOAT is true, and TARGET_HARD_FLOAT_ABI
is true too.
2021-03-30 Richard Earnshaw <rearnsha@arm.com>
gcc/
PR target/99773
* config/arm/arm.c (arm_file_start): Fix emission of
Tag_ABI_VFP_args attribute.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug target/99773] ARM v8.1-m MVE interaction with -mfloat-abi not clear
2021-03-25 16:26 [Bug target/99773] New: ARM v8.1-m MVE interaction with -mfloat-abi not clear clyon at gcc dot gnu.org
` (5 preceding siblings ...)
2021-03-30 13:11 ` cvs-commit at gcc dot gnu.org
@ 2021-03-30 13:12 ` clyon at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: clyon at gcc dot gnu.org @ 2021-03-30 13:12 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99773
Christophe Lyon <clyon at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
--- Comment #7 from Christophe Lyon <clyon at gcc dot gnu.org> ---
Fixed
^ permalink raw reply [flat|nested] 8+ messages in thread
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2021-03-25 16:26 [Bug target/99773] New: ARM v8.1-m MVE interaction with -mfloat-abi not clear clyon at gcc dot gnu.org
2021-03-25 16:49 ` [Bug target/99773] " rearnsha at gcc dot gnu.org
2021-03-25 16:58 ` acoplan at gcc dot gnu.org
2021-03-25 17:57 ` clyon at gcc dot gnu.org
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