So far atomic objects are aligned according to their default alignment. For 128 bit scalar types like int128 or long double this results in an 8 byte alignment which is wrong and must be 16 byte.
libstdc++ already computes a correct alignment, though, still adding a test case in order to make sure that both implementations are compatible. Bootstrapped and regtested. Ok for mainline? Since this is an ABI break, is a backport to GCC 13 reasonable? gcc/ChangeLog: * config/s390/s390.cc (TARGET_ATOMIC_ALIGN_FOR_MODE): New. (s390_atomic_align_for_mode): New. gcc/testsuite/ChangeLog: * g++.target/s390/atomic-align-1.C: New test. * gcc.target/s390/atomic-align-1.c: New test. * gcc.target/s390/atomic-align-2.c: New test. --- gcc/config/s390/s390.cc | 8 ++++++ .../g++.target/s390/atomic-align-1.C | 25 +++++++++++++++++++ .../gcc.target/s390/atomic-align-1.c | 23 +++++++++++++++++ .../gcc.target/s390/atomic-align-2.c | 18 +++++++++++++ 4 files changed, 74 insertions(+) create mode 100644 gcc/testsuite/g++.target/s390/atomic-align-1.C create mode 100644 gcc/testsuite/gcc.target/s390/atomic-align-1.c create mode 100644 gcc/testsuite/gcc.target/s390/atomic-align-2.c diff --git a/gcc/config/s390/s390.cc b/gcc/config/s390/s390.cc index 505de995da8..4813bf91dc4 100644 --- a/gcc/config/s390/s390.cc +++ b/gcc/config/s390/s390.cc @@ -450,6 +450,14 @@ s390_preserve_fpr_arg_p (int regno) && regno >= FPR0_REGNUM); } +#undef TARGET_ATOMIC_ALIGN_FOR_MODE +#define TARGET_ATOMIC_ALIGN_FOR_MODE s390_atomic_align_for_mode +static unsigned int +s390_atomic_align_for_mode (machine_mode mode) +{ + return GET_MODE_BITSIZE (mode); +} + /* A couple of shortcuts. */ #define CONST_OK_FOR_J(x) \ CONST_OK_FOR_CONSTRAINT_P((x), 'J', "J") diff --git a/gcc/testsuite/g++.target/s390/atomic-align-1.C b/gcc/testsuite/g++.target/s390/atomic-align-1.C new file mode 100644 index 00000000000..43aa0bc39ed --- /dev/null +++ b/gcc/testsuite/g++.target/s390/atomic-align-1.C @@ -0,0 +1,25 @@ +/* { dg-do compile { target int128 } } */ +/* { dg-options "-std=c++11" } */ +/* { dg-final { scan-assembler-times {\.align\t2} 2 } } */ +/* { dg-final { scan-assembler-times {\.align\t4} 2 } } */ +/* { dg-final { scan-assembler-times {\.align\t8} 3 } } */ +/* { dg-final { scan-assembler-times {\.align\t16} 2 } } */ + +#include <atomic> + +// 2 +std::atomic<char> var_char; +std::atomic<short> var_short; +// 4 +std::atomic<int> var_int; +// 8 +std::atomic<long> var_long; +std::atomic<long long> var_long_long; +// 16 +std::atomic<__int128> var_int128; +// 4 +std::atomic<float> var_float; +// 8 +std::atomic<double> var_double; +// 16 +std::atomic<long double> var_long_double; diff --git a/gcc/testsuite/gcc.target/s390/atomic-align-1.c b/gcc/testsuite/gcc.target/s390/atomic-align-1.c new file mode 100644 index 00000000000..b2e1233e3ee --- /dev/null +++ b/gcc/testsuite/gcc.target/s390/atomic-align-1.c @@ -0,0 +1,23 @@ +/* { dg-do compile { target int128 } } */ +/* { dg-options "-std=c11" } */ +/* { dg-final { scan-assembler-times {\.align\t2} 2 } } */ +/* { dg-final { scan-assembler-times {\.align\t4} 2 } } */ +/* { dg-final { scan-assembler-times {\.align\t8} 3 } } */ +/* { dg-final { scan-assembler-times {\.align\t16} 2 } } */ + +// 2 +_Atomic char var_char; +_Atomic short var_short; +// 4 +_Atomic int var_int; +// 8 +_Atomic long var_long; +_Atomic long long var_long_long; +// 16 +_Atomic __int128 var_int128; +// 4 +_Atomic float var_float; +// 8 +_Atomic double var_double; +// 16 +_Atomic long double var_long_double; diff --git a/gcc/testsuite/gcc.target/s390/atomic-align-2.c b/gcc/testsuite/gcc.target/s390/atomic-align-2.c new file mode 100644 index 00000000000..0bf17341bf8 --- /dev/null +++ b/gcc/testsuite/gcc.target/s390/atomic-align-2.c @@ -0,0 +1,18 @@ +/* { dg-do compile { target int128 } } */ +/* { dg-options "-O -std=c11" } */ +/* { dg-final { scan-assembler-not {abort} } } */ + +/* The stack is 8 byte aligned which means GCC has to manually align a 16 byte + aligned object. This is done by allocating not 16 but rather 24 bytes for + variable X and then manually aligning a pointer inside the memory block. + Validate this by ensuring that the if-statement is optimized out. */ + +void bar (_Atomic unsigned __int128 *ptr); + +void foo (void) { + _Atomic unsigned __int128 x; + unsigned long n = (unsigned long)&x; + if (n % 16 != 0) + __builtin_abort (); + bar (&x); +} -- 2.39.2