Forgot the reference:
[1] https://gcc.gnu.org/ml/gcc-patches/2018-12/msg01308.html
On Monday, 31 December 2018, Thomas Preudhomme <thomas.preudho...@linaro.org>
wrote:
> Hi Richard,
>
> On Thursday, 20 December 2018, Richard Earnshaw (lists) <
richard.earns...@arm.com> wrote:
>> On 14/12/2018 23:28, Thomas Preudhomme wrote:
>>> Hi,
>>>
>>> Commit r242693 forced fp to be saved/restored when needed due to an
>>> instance of GCC using fp as a scratch register to save sp while it's
>>> being clobbered by an inline asm. The normal path in
>>> thumb1_compute_save_reg_mask saving callee-saved registers which are
>>> live in the function does not work in that case because fp is chosen to
>>> hold sp after that function is called.
>>>
>>> Since clobbering sp is now errored out by the compiler and this was the
>>> only case reported where fp was live but not marked as such when
>>> thumb1_compute_save_reg_mask is called, I believe the whole commit
>>> r242693 should be reverted.
>>>
>>> ChangeLog entries are as follows:
>>>
>>> *** gcc/ChangeLog ***
>>>
>>> 2018-12-14 Thomas Preud'homme <thomas.preudho...@arm.com>
>>>
>>> Revert:
>>> 2016-11-22 Thomas Preud'homme <thomas.preudho...@arm.com>
>>>
>>> PR target/77904
>>> * config/arm/arm.c (thumb1_compute_save_reg_mask): Mark frame
pointer
>>> in save register mask if it is needed.
>>>
>>> *** gcc/testsuite/ChangeLog ***
>>>
>>> 2018-12-14 Thomas Preud'homme <thomas.preudho...@arm.com>
>>>
>>> Revert:
>>> 2016-11-22 Thomas Preud'homme <thomas.preudho...@arm.com>
>>>
>>> PR target/77904
>>> * gcc.target/arm/pr77904.c: New test.
>>>
>>> Testing: Built an arm-none-eabi GCC cross-compiler targeting Armv6S-M
>>> and regression testsuite does not show any regression.
>>>
>>> Ok for stage3?
>>
>> OK.
>>
>> R.
>
> Bernd suggested in [1] that the behaviour tested by pr77904.c might
actually be a behaviour we can allow with a patch to add a dg-warning to
the decade. I'll wait for a resolution on that suggestion before deciding
whether to commit this.
>
> Best regards,
>
> Thomas
>
>>
>>>
>>> Best regards,
>>>
>>> Thomas
>>>
>>>
>>> fix_pr77904_test_failure.patch
>>>
>>> From 63c52e7bf932947be7122cdc63f6cdc913479259 Mon Sep 17 00:00:00 2001
>>> From: Thomas Preud'homme <thomas.preudho...@linaro.org>
>>> Date: Fri, 14 Dec 2018 16:02:59 +0000
>>> Subject: [PATCH] [PATCH, ARM] Fix PR77904 testcase failure
>>>
>>> Hi,
>>>
>>> Commit r242693 forced fp to be saved/restored when needed due to an
>>> instance of GCC using fp as a scratch register to save sp while it's
>>> being clobbered by an inline asm. The normal path in
>>> thumb1_compute_save_reg_mask saving callee-saved registers which are
>>> live in the function does not work in that case because fp is chosen to
>>> hold sp after that function is called.
>>>
>>> Since clobbering sp is now errored out by the compiler and this was the
>>> only case reported where fp was live but not marked as such when
>>> thumb1_compute_save_reg_mask is called, I believe the whole commit
>>> r242693 should be reverted.
>>>
>>> ChangeLog entries are as follows:
>>>
>>> *** gcc/ChangeLog ***
>>>
>>> 2018-12-14 Thomas Preud'homme <thomas.preudho...@arm.com>
>>>
>>> Revert:
>>> 2016-11-22 Thomas Preud'homme <thomas.preudho...@arm.com>
>>>
>>> PR target/77904
>>> * config/arm/arm.c (thumb1_compute_save_reg_mask): Mark frame
pointer
>>> in save register mask if it is needed.
>>>
>>> *** gcc/testsuite/ChangeLog ***
>>>
>>> 2018-12-14 Thomas Preud'homme <thomas.preudho...@arm.com>
>>>
>>> Revert:
>>> 2016-11-22 Thomas Preud'homme <thomas.preudho...@arm.com>
>>>
>>> PR target/77904
>>> * gcc.target/arm/pr77904.c: New test.
>>>
>>> Testing: Built an arm-none-eabi GCC cross-compiler targeting Armv6S-M
>>> and regression testsuite does not show any regression.
>>>
>>> Ok for stage3?
>>>
>>> Best regards,
>>>
>>> Thomas
>>> ---
>>> gcc/ChangeLog | 9 ++++++
>>> gcc/config/arm/arm.c | 4 ---
>>> gcc/testsuite/ChangeLog | 8 +++++
>>> gcc/testsuite/gcc.target/arm/pr77904.c | 45 --------------------------
>>> 4 files changed, 17 insertions(+), 49 deletions(-)
>>> delete mode 100644 gcc/testsuite/gcc.target/arm/pr77904.c
>>>
>>> diff --git a/gcc/ChangeLog b/gcc/ChangeLog
>>> index d8e374fb15f..9caeb1d5e18 100644
>>> --- a/gcc/ChangeLog
>>> +++ b/gcc/ChangeLog
>>> @@ -1,3 +1,12 @@
>>> +2018-12-14 Thomas Preud'homme <thomas.preudho...@arm.com>
>>> +
>>> + Revert:
>>> + 2016-11-22 Thomas Preud'homme <thomas.preudho...@arm.com>
>>> +
>>> + PR target/77904
>>> + * config/arm/arm.c (thumb1_compute_save_reg_mask): Mark frame
pointer
>>> + in save register mask if it is needed.
>>> +
>>> 2018-11-27 Alan Modra <amo...@gmail.com>
>>>
>>> * config/rs6000/aix71.h (ASM_SPEC): Don't select default -maix64
>>> diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
>>> index 40f0574e32e..2ab5d8abc33 100644
>>> --- a/gcc/config/arm/arm.c
>>> +++ b/gcc/config/arm/arm.c
>>> @@ -19553,10 +19553,6 @@ thumb1_compute_save_core_reg_mask (void)
>>> if (df_regs_ever_live_p (reg) && callee_saved_reg_p (reg))
>>> mask |= 1 << reg;
>>>
>>> - /* Handle the frame pointer as a special case. */
>>> - if (frame_pointer_needed)
>>> - mask |= 1 << HARD_FRAME_POINTER_REGNUM;
>>> -
>>> if (flag_pic
>>> && !TARGET_SINGLE_PIC_BASE
>>> && arm_pic_register != INVALID_REGNUM
>>> diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
>>> index 9e1f6d05a45..4e58c8940da 100644
>>> --- a/gcc/testsuite/ChangeLog
>>> +++ b/gcc/testsuite/ChangeLog
>>> @@ -1,3 +1,11 @@
>>> +2018-12-14 Thomas Preud'homme <thomas.preudho...@arm.com>
>>> +
>>> + Revert:
>>> + 2016-11-22 Thomas Preud'homme <thomas.preudho...@arm.com>
>>> +
>>> + PR target/77904
>>> + * gcc.target/arm/pr77904.c: New test.
>>> +
>>> 2018-11-27 Jozef Lawrynowicz <joze...@mittosystems.com>
>>>
>>> * lib/target-supports.exp
>>> diff --git a/gcc/testsuite/gcc.target/arm/pr77904.c
b/gcc/testsuite/gcc.target/arm/pr77904.c
>>> deleted file mode 100644
>>> index 76728c07e73..00000000000
>>> --- a/gcc/testsuite/gcc.target/arm/pr77904.c
>>> +++ /dev/null
>>> @@ -1,45 +0,0 @@
>>> -/* { dg-do run } */
>>> -/* { dg-options "-O2" } */
>>> -
>>> -__attribute__ ((noinline, noclone)) void
>>> -clobber_sp (void)
>>> -{
>>> - __asm volatile ("" : : : "sp");
>>> -}
>>> -
>>> -int
>>> -main (void)
>>> -{
>>> - int ret;
>>> -
>>> - __asm volatile ("mov\tr4, #0xf4\n\t"
>>> - "mov\tr5, #0xf5\n\t"
>>> - "mov\tr6, #0xf6\n\t"
>>> - "mov\tr7, #0xf7\n\t"
>>> - "mov\tr0, #0xf8\n\t"
>>> - "mov\tr8, r0\n\t"
>>> - "mov\tr0, #0xfa\n\t"
>>> - "mov\tr10, r0"
>>> - : : : "r0", "r4", "r5", "r6", "r7", "r8", "r10");
>>> - clobber_sp ();
>>> -
>>> - __asm volatile ("cmp\tr4, #0xf4\n\t"
>>> - "bne\tfail\n\t"
>>> - "cmp\tr5, #0xf5\n\t"
>>> - "bne\tfail\n\t"
>>> - "cmp\tr6, #0xf6\n\t"
>>> - "bne\tfail\n\t"
>>> - "cmp\tr7, #0xf7\n\t"
>>> - "bne\tfail\n\t"
>>> - "mov\tr0, r8\n\t"
>>> - "cmp\tr0, #0xf8\n\t"
>>> - "bne\tfail\n\t"
>>> - "mov\tr0, r10\n\t"
>>> - "cmp\tr0, #0xfa\n\t"
>>> - "bne\tfail\n\t"
>>> - "mov\t%0, #1\n"
>>> - "fail:\n\t"
>>> - "sub\tr0, #1"
>>> - : "=r" (ret) : :);
>>> - return ret;
>>> -}
>>>
>>
>>
