scchan added inline comments.
================ Comment at: clang/docs/AMDGPUSupport.rst:47 + * - ``__amdgcn_feature_<feature-name>__`` + - Defined for each supported target feature. The value is 1 if the feature is enabled and 0 if it is disabled. Allowed feature names are sramecc and xnack. + * - ``__AMDGCN_CUMODE__`` ---------------- yaxunl wrote: > scchan wrote: > > This set of feature macros is tricky. A feature macro is defined only when > > the corresponding target feature has been explicitly specified during > > compilation; otherwise it's undefined. Users will have to refer to the > > target feature table to get the semantic of each state. For example, for > > xnack, undefined=="any", 1 for xnack+, 0 for xnack-. > > > > Is there a reason we don't support features other than sramecc and xnack? > This macro is designed to support Target ID only, therefore it is only > emitted when target ID containing the feature is used. > > The target ID features are stable since they are used to select code objects > from fat binaries. > > My understanding is that other features used by amdgpu backend do not have > stable feature names, therefore are not suitable to be used as predefined > macros for users to condition their code. The current wording seems to imply that a feature macro is always defined if that target feature is supported but that's not the case. For example, the macro __amdgcn_feature_xnack__ is undefined if a user compiles for xnack="any". Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D154133/new/ https://reviews.llvm.org/D154133 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
