From: Jason Merrill <jason@redhat.com>
Date: Wed, 15 Sep 2021 13:30:10 +0000 (-0400)
Subject: c++: don't warn about internal interference sizes
X-Git-Tag: basepoints/gcc-13~4761
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4320a4b717dcccddf230d0b944bfc5a7ae282508;p=thirdparty%2Fgcc.git

c++: don't warn about internal interference sizes

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.
---

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 1a2925b41087..9ad9446e262e 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;
 }