[PATCH, ARM 3/7, ping3] Refactor atomic compare_and_swap to make it fit for ARMv8-M Baseline

Kyrill Tkachov kyrylo.tkachov@foss.arm.com
Wed Oct 26 15:47:00 GMT 2016


Hi Thomas,

On 24/10/16 09:05, Thomas Preudhomme wrote:
> Ping?
>
> Best regards,
>
> Thomas
>
> On 14/10/16 14:50, Thomas Preudhomme wrote:
>> Ping?
>>
>> Best regards,
>>
>> Thomas
>>
>> On 03/10/16 17:44, Thomas Preudhomme wrote:
>>> Ping?
>>>
>>> Best regards,
>>>
>>> Thomas
>>>
>>> On 22/09/16 14:44, Thomas Preudhomme wrote:
>>>> Hi,
>>>>
>>>> This patch is part of a patch series to add support for atomic operations on
>>>> ARMv8-M Baseline targets in GCC. This specific patch refactors the expander and
>>>> splitter for atomics to make the logic work with ARMv8-M Baseline which has
>>>> limitation of Thumb-1 in terms of CC flag setting and different conditional
>>>> compare insn patterns.
>>>>
>>>> ChangeLog entry is as follows:
>>>>
>>>> *** gcc/ChangeLog ***
>>>>
>>>> 2016-09-02  Thomas Preud'homme <thomas.preudhomme@arm.com>
>>>>
>>>>         * config/arm/arm.c (arm_expand_compare_and_swap): Add new bdst local
>>>>         variable.  Add the new parameter to the insn generator.  Set that
>>>>         parameter to be CC flag for 32-bit targets, bval otherwise.  Set the
>>>>         return value from the negation of that parameter for Thumb-1, keeping
>>>>         the logic unchanged otherwise except for using bdst as the destination
>>>>         register of the compare_and_swap insn.
>>>>         (arm_split_compare_and_swap): Add explanation about how is the value
>>>>         returned to the function comment.  Rename scratch variable to
>>>>         neg_bval.  Adapt initialization of variables holding operands to the
>>>>         new operand numbers.  Use return register to hold result of store
>>>>         exclusive for Thumb-1, scratch register otherwise. Construct the
>>>>         appropriate cbranch for Thumb-1 targets, keeping the logic unchanged
>>>>         for 32-bit targets.  Guard Z flag setting to restrict to 32bit targets.
>>>>         Use gen_cbranchsi4 rather than hand-written conditional branch to loop
>>>>         for strongly ordered compare_and_swap.
>>>>         * config/arm/predicates.md (cc_register_operand): New predicate.
>>>>         * config/arm/sync.md (atomic_compare_and_swap<mode>_1): Use a
>>>>         match_operand with the new predicate to accept either the CC flag or a
>>>>         destination register for the boolean return value, restricting it to
>>>>         CC flag only via constraint.  Adapt operand numbers accordingly.
>>>>
>>>>
>>>> Testing: No code generation difference for ARMv7-A, ARMv7VE and ARMv8-A on all
>>>> atomic and synchronization testcases in the testsuite [2]. Patchset was also
>>>> bootstrapped with --enable-itm --enable-gomp on ARMv8-A in ARM and Thumb mode at
>>>> optimization level -O1 and above [1] without any regression in the testsuite and
>>>> no code generation difference in libitm and libgomp.
>>>>
>>>> Code generation for ARMv8-M Baseline has been manually examined and compared
>>>> against ARMv8-A Thumb-2 for the following configuration without finding any
>>>> issue:
>>>>
>>>> gcc.dg/atomic-op-2.c at -Os
>>>> gcc.dg/atomic-compare-exchange-2.c at -Os
>>>> gcc.dg/atomic-compare-exchange-3.c at -O3
>>>>
>>>>
>>>> Is this ok for trunk?
>>>>

This is ok.
Thanks,
Kyrill


>>>> Best regards,
>>>>
>>>> Thomas
>>>>
>>>> [1] CFLAGS_FOR_TARGET and CXXFLAGS_FOR_TARGET were set to "-O1 -g", "-O3 -g" and
>>>> undefined ("-O2 -g")
>>>> [2] The exact list is:
>>>>
>>>> gcc/testsuite/gcc.dg/atomic-compare-exchange-1.c
>>>> gcc/testsuite/gcc.dg/atomic-compare-exchange-2.c
>>>> gcc/testsuite/gcc.dg/atomic-compare-exchange-3.c
>>>> gcc/testsuite/gcc.dg/atomic-exchange-1.c
>>>> gcc/testsuite/gcc.dg/atomic-exchange-2.c
>>>> gcc/testsuite/gcc.dg/atomic-exchange-3.c
>>>> gcc/testsuite/gcc.dg/atomic-fence.c
>>>> gcc/testsuite/gcc.dg/atomic-flag.c
>>>> gcc/testsuite/gcc.dg/atomic-generic.c
>>>> gcc/testsuite/gcc.dg/atomic-generic-aux.c
>>>> gcc/testsuite/gcc.dg/atomic-invalid-2.c
>>>> gcc/testsuite/gcc.dg/atomic-load-1.c
>>>> gcc/testsuite/gcc.dg/atomic-load-2.c
>>>> gcc/testsuite/gcc.dg/atomic-load-3.c
>>>> gcc/testsuite/gcc.dg/atomic-lockfree.c
>>>> gcc/testsuite/gcc.dg/atomic-lockfree-aux.c
>>>> gcc/testsuite/gcc.dg/atomic-noinline.c
>>>> gcc/testsuite/gcc.dg/atomic-noinline-aux.c
>>>> gcc/testsuite/gcc.dg/atomic-op-1.c
>>>> gcc/testsuite/gcc.dg/atomic-op-2.c
>>>> gcc/testsuite/gcc.dg/atomic-op-3.c
>>>> gcc/testsuite/gcc.dg/atomic-op-6.c
>>>> gcc/testsuite/gcc.dg/atomic-store-1.c
>>>> gcc/testsuite/gcc.dg/atomic-store-2.c
>>>> gcc/testsuite/gcc.dg/atomic-store-3.c
>>>> gcc/testsuite/g++.dg/ext/atomic-1.C
>>>> gcc/testsuite/g++.dg/ext/atomic-2.C
>>>> gcc/testsuite/gcc.target/arm/atomic-comp-swap-release-acquire.c
>>>> gcc/testsuite/gcc.target/arm/atomic-op-acq_rel.c
>>>> gcc/testsuite/gcc.target/arm/atomic-op-acquire.c
>>>> gcc/testsuite/gcc.target/arm/atomic-op-char.c
>>>> gcc/testsuite/gcc.target/arm/atomic-op-consume.c
>>>> gcc/testsuite/gcc.target/arm/atomic-op-int.c
>>>> gcc/testsuite/gcc.target/arm/atomic-op-relaxed.c
>>>> gcc/testsuite/gcc.target/arm/atomic-op-release.c
>>>> gcc/testsuite/gcc.target/arm/atomic-op-seq_cst.c
>>>> gcc/testsuite/gcc.target/arm/atomic-op-short.c
>>>> gcc/testsuite/gcc.target/arm/atomic_loaddi_1.c
>>>> gcc/testsuite/gcc.target/arm/atomic_loaddi_2.c
>>>> gcc/testsuite/gcc.target/arm/atomic_loaddi_3.c
>>>> gcc/testsuite/gcc.target/arm/atomic_loaddi_4.c
>>>> gcc/testsuite/gcc.target/arm/atomic_loaddi_5.c
>>>> gcc/testsuite/gcc.target/arm/atomic_loaddi_6.c
>>>> gcc/testsuite/gcc.target/arm/atomic_loaddi_7.c
>>>> gcc/testsuite/gcc.target/arm/atomic_loaddi_8.c
>>>> gcc/testsuite/gcc.target/arm/atomic_loaddi_9.c
>>>> gcc/testsuite/gcc.target/arm/sync-1.c
>>>> gcc/testsuite/gcc.target/arm/synchronize.c
>>>> gcc/testsuite/gcc.target/arm/armv8-sync-comp-swap.c
>>>> gcc/testsuite/gcc.target/arm/armv8-sync-op-acquire.c
>>>> gcc/testsuite/gcc.target/arm/armv8-sync-op-full.c
>>>> gcc/testsuite/gcc.target/arm/armv8-sync-op-release.c
>>>> libstdc++-v3/testsuite/29_atomics/atomic/60658.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/62259.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/64658.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/65147.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/65913.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/70766.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/cons/49445.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/cons/constexpr.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/cons/copy_list.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/cons/default.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/cons/direct_list.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/cons/single_value.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/cons/user_pod.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/operators/51811.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/operators/56011.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/operators/integral_assignment.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/operators/integral_conversion.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/operators/pointer_partial_void.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/requirements/base_classes.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic/requirements/compare_exchange_lowering.cc
>>>>
>>>>
>>>> libstdc++-v3/testsuite/29_atomics/atomic/requirements/explicit_instantiation/1.cc
>>>>
>>>> libstdc++-v3/testsuite/29_atomics/atomic_flag/clear/1.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_flag/cons/1.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_flag/cons/56012.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_flag/cons/aggregate.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_flag/cons/default.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_flag/requirements/standard_layout.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_flag/requirements/trivial.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_flag/test_and_set/explicit.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_flag/test_and_set/implicit.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_integral/60940.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_integral/65147.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_integral/cons/constexpr.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_integral/cons/copy_list.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_integral/cons/default.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_integral/cons/direct_list.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_integral/cons/single_value.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_integral/operators/bitwise.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_integral/operators/decrement.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_integral/operators/increment.cc
>>>> libstdc++-v3/testsuite/29_atomics/atomic_integral/operators/integral_assignment.cc
>>>>
>>>>
>>>> libstdc++-v3/testsuite/29_atomics/atomic_integral/operators/integral_conversion.cc
>>>>
>>>>
>>>> libstdc++-v3/testsuite/29_atomics/atomic_integral/requirements/standard_layout.cc
>>>>
>>>> libstdc++-v3/testsuite/29_atomics/atomic_integral/requirements/trivial.cc
>>>> libstdc++-v3/testsuite/29_atomics/headers/atomic/functions_std_c++0x.cc
>>>> libstdc++-v3/testsuite/29_atomics/headers/atomic/macros.cc
>>>> libstdc++-v3/testsuite/29_atomics/headers/atomic/types_std_c++0x.cc



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