| Message ID | 20210915153154.1111443-1-jason@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [pushed] c++: don't warn about internal interference sizes | expand |
On 9/15/2021 9:31 AM, Jason Merrill via Gcc-patches wrote: > Most any compilation on ARM/AArch64 was warning because the default L1 cache > line size of 32B was smaller than the default > std::hardware_constructive_interference_size of 64B. This is mostly due to > inaccurate --param l1-cache-line-size, but it's not helpful to complain to a > user that didn't set the values. > > gcc/cp/ChangeLog: > > * decl.c (cxx_init_decl_processing): Only warn about odd > interference sizes if they were specified with --param. I wonder if that'll fix the arm-linux build failures that started showing up recently: armeb-linux-gnueabi: <built-in>: error: '--param constructive-interference-size=64' is greater than '--param l1-cache-line-size=32' [-Werror=interference-size] I expect the other arm- linux configurations would show it as well, but they're only run once a week in my tester and I don't think they've been run since the recent changes in this space. jeff
On Wed, Sep 15, 2021 at 11:37 AM Jeff Law <jeffreyalaw@gmail.com> wrote: > > > On 9/15/2021 9:31 AM, Jason Merrill via Gcc-patches wrote: > > Most any compilation on ARM/AArch64 was warning because the default L1 > cache > > line size of 32B was smaller than the default > > std::hardware_constructive_interference_size of 64B. This is mostly due > to > > inaccurate --param l1-cache-line-size, but it's not helpful to complain > to a > > user that didn't set the values. > > > > gcc/cp/ChangeLog: > > > > * decl.c (cxx_init_decl_processing): Only warn about odd > > interference sizes if they were specified with --param. > I wonder if that'll fix the arm-linux build failures that started > showing up recently: > > armeb-linux-gnueabi: > > <built-in>: error: '--param constructive-interference-size=64' is > greater than '--param l1-cache-line-size=32' [-Werror=interference-size] > > I expect the other arm- linux configurations would show it as well, but > they're only run once a week in my tester and I don't think they've been > run since the recent changes in this space. > Yes, that is exactly the purpose of this change. Jason
On Wed, Sep 15, 2021 at 5:39 PM Jason Merrill via Gcc-patches < gcc-patches@gcc.gnu.org> wrote: > On Wed, Sep 15, 2021 at 11:37 AM Jeff Law <jeffreyalaw@gmail.com> wrote: > > > > > > > On 9/15/2021 9:31 AM, Jason Merrill via Gcc-patches wrote: > > > Most any compilation on ARM/AArch64 was warning because the default L1 > > cache > > > line size of 32B was smaller than the default > > > std::hardware_constructive_interference_size of 64B. This is mostly > due > > to > > > inaccurate --param l1-cache-line-size, but it's not helpful to complain > > to a > > > user that didn't set the values. > > > > > > gcc/cp/ChangeLog: > > > > > > * decl.c (cxx_init_decl_processing): Only warn about odd > > > interference sizes if they were specified with --param. > > I wonder if that'll fix the arm-linux build failures that started > > showing up recently: > > > > armeb-linux-gnueabi: > > > > <built-in>: error: '--param constructive-interference-size=64' is > > greater than '--param l1-cache-line-size=32' [-Werror=interference-size] > > > > I expect the other arm- linux configurations would show it as well, but > > they're only run once a week in my tester and I don't think they've been > > run since the recent changes in this space. > > > > Yes, that is exactly the purpose of this change. > > I can confirm that those targets build again, thanks. > Jason >
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c index 1a2925b4108..9ad9446e262 100644 --- a/gcc/cp/decl.c +++ b/gcc/cp/decl.c @@ -4756,7 +4756,7 @@ cxx_init_decl_processing (void) /* Check that the hardware interference sizes are at least alignof(max_align_t), as required by the standard. */ const int max_align = max_align_t_align () / BITS_PER_UNIT; - if (param_destruct_interfere_size) + if (global_options_set.x_param_destruct_interfere_size) { if (param_destruct_interfere_size < max_align) error ("%<--param destructive-interference-size=%d%> is less than " @@ -4767,11 +4767,13 @@ cxx_init_decl_processing (void) "is less than %<--param l1-cache-line-size=%d%>", param_destruct_interfere_size, param_l1_cache_line_size); } + else if (param_destruct_interfere_size) + /* Assume the internal value is OK. */; else if (param_l1_cache_line_size >= max_align) param_destruct_interfere_size = param_l1_cache_line_size; /* else leave it unset. */ - if (param_construct_interfere_size) + if (global_options_set.x_param_construct_interfere_size) { if (param_construct_interfere_size < max_align) error ("%<--param constructive-interference-size=%d%> is less than " @@ -4783,6 +4785,8 @@ cxx_init_decl_processing (void) "is greater than %<--param l1-cache-line-size=%d%>", param_construct_interfere_size, param_l1_cache_line_size); } + else if (param_construct_interfere_size) + /* Assume the internal value is OK. */; else if (param_l1_cache_line_size >= max_align) param_construct_interfere_size = param_l1_cache_line_size; }