[gentoo-dev] [PATCH] rocm.eclass: add rocm_use_hipcc function and update example accordingly

["Sv. Lockal" <lockalsash@gmail.com>]

This adds a new function rocm_use_hipcc in rocm.eclass to be used in
every src_configure, where the compiler is switched to hipcc (a. k. a.
clang with extra flags).

Github pull request: https://github.com/gentoo/gentoo/pull/37639
Bug: https://bugs.gentoo.org/936099
Signed-off-by: Sv. Lockal <lockalsash@gmail.com>
---
 eclass/rocm.eclass | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/eclass/rocm.eclass b/eclass/rocm.eclass
index 7039455dec6b5..44ddf4fd09a87 100644
--- a/eclass/rocm.eclass
+++ b/eclass/rocm.eclass
@@ -15,9 +15,13 @@
 # edit USE flag to control which GPU architecture to compile. Using
 # ${ROCM_USEDEP} can ensure coherence among dependencies. Ebuilds can call the
 # function get_amdgpu_flag to translate activated target to GPU compile flags,
-# passing it to configuration. Function check_amdgpu can help ebuild ensure
+# passing it to configuration. Function rocm_use_hipcc switches active compiler
+# to hipcc and cleans incompatible flags (useful for users with gcc-only flags
+# in /etc/portage/make.conf). Function check_amdgpu can help ebuild ensure
 # read and write permissions to GPU device in src_test phase, throwing friendly
-# error message if unavailable.
+# error message if unavailable. However src_configure in general should not
+# access any GPU devices. If it does, it usually means that CMakeLists.txt
+# ignores AMDGPU_TARGETS in favor of autodetected GPU, which is not desired.
 #
 # @EXAMPLE:
 # Example ebuild for ROCm library in https://github.com/ROCmSoftwarePlatform
@@ -39,14 +43,12 @@
 # "
 #
 # src_configure() {
-#     # avoid sandbox violation
-#     addpredict /dev/kfd
-#     addpredict /dev/dri/
+#     rocm_use_hipcc
 #     local mycmakeargs=(
 #         -DAMDGPU_TARGETS="$(get_amdgpu_flags)"
 #         -DBUILD_CLIENTS_TESTS=$(usex test ON OFF)
 #     )
-#     CXX=hipcc cmake_src_configure
+#     cmake_src_configure
 # }
 #
 # src_test() {
@@ -90,6 +92,8 @@ esac
 if [[ ! ${_ROCM_ECLASS} ]]; then
 _ROCM_ECLASS=1

+inherit flag-o-matic
+
 # @ECLASS_VARIABLE: ROCM_VERSION
 # @REQUIRED
 # @PRE_INHERIT
@@ -231,3 +235,12 @@ check_amdgpu() {
 }

 fi
+
+# @FUNCTION: rocm_use_hipcc
+# @USAGE: rocm_use_hipcc
+# @DESCRIPTION:
+# switch active C and C++ compilers to hipcc and clean unsupported flags.
+rocm_use_hipcc() {
+ export CC=hipcc CXX=hipcc
+ strip-unsupported-flags
+}