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

Fri Oct 14 13:50:00 GMT 2016

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?
>>
>> 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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