https://gcc.gnu.org/g:fe5c59ea997316da471de29f5720b650114035e9
commit r16-5799-gfe5c59ea997316da471de29f5720b650114035e9 Author: Andrew Stubbs <[email protected]> Date: Fri Nov 28 16:20:46 2025 +0000 libgomp, amdgcn: document HSA_XNACK Mention that the HSA_XNACK variable is automatically set by the toolchain. libgomp/ChangeLog: * libgomp.texi (AMD GCN): Mention HSA_XNACK is set automatically. Diff: --- libgomp/libgomp.texi | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/libgomp/libgomp.texi b/libgomp/libgomp.texi index abe8ef75d8e7..ac96d2f29c76 100644 --- a/libgomp/libgomp.texi +++ b/libgomp/libgomp.texi @@ -7157,13 +7157,14 @@ The implementation remark: such that the next reverse offload region is only executed after the previous one returned. @item OpenMP code that has a @code{requires} directive with @code{self_maps} or - @code{unified_shared_memory} is only supported if all AMD GPUs have the - @code{HSA_AMD_SYSTEM_INFO_SVM_ACCESSIBLE_BY_DEFAULT} property; for - discrete GPUs, this may require setting the @code{HSA_XNACK} environment - variable to @samp{1}; for systems with both an APU and a discrete GPU that - does not support XNACK, consider using @code{ROCR_VISIBLE_DEVICES} to - enable only the APU. If not supported, all AMD GPU devices are removed - from the list of available devices (``host fallback''). + @code{unified_shared_memory} is only supported if @emph{all} the AMD GPUs + present have the @code{HSA_AMD_SYSTEM_INFO_SVM_ACCESSIBLE_BY_DEFAULT} + property; some systems require the "xnack" feature enabled for this to be + true, in which case the runtime will attempt to set the @code{HSA_XNACK} + environment variable to @samp{1} automatically (user-set values are not + overridden, and the setting only affects the executable itself and any + child processes). If any AMD GPU device is not supported, all AMD GPUs + are removed from the list of available devices (``host fallback''). @item The available stack size can be changed using the @code{GCN_STACK_SIZE} environment variable; the default is 32 kiB per thread. @item Low-latency memory (@code{omp_low_lat_mem_space}) is supported when the
