From f047ca31114d5749386660d65b7166e82e82d058 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20M=C3=BCtzel?= <markus.muetzel@gmx.de>
Date: Sat, 5 Aug 2023 13:32:20 +0200
Subject: [PATCH 1/4] cmake: Check for Fortran compiler early on

---
 CMakeLists.txt      | 11 +++++++++++
 cmake/f_check.cmake |  7 +------
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 35077f3c2..f3cb0eed4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -93,6 +93,17 @@ endif()
 
 message(WARNING "CMake support is experimental. It does not yet support all build options and may not produce the same Makefiles that OpenBLAS ships with.")
 
+if(NOT NOFORTRAN)
+  # Check for working Fortran compiler
+  include(CheckLanguage)
+  check_language(Fortran)
+  if(CMAKE_Fortran_COMPILER)
+    enable_language(Fortran)
+  else()
+    set(NOFORTRAN 1)
+  endif()
+endif()
+
 include("${PROJECT_SOURCE_DIR}/cmake/utils.cmake")
 include("${PROJECT_SOURCE_DIR}/cmake/system.cmake")
 
diff --git a/cmake/f_check.cmake b/cmake/f_check.cmake
index df3a4858d..df9716cb7 100644
--- a/cmake/f_check.cmake
+++ b/cmake/f_check.cmake
@@ -20,12 +20,7 @@
 # NEEDBUNDERSCORE
 # NEED2UNDERSCORES
 
-include(CheckLanguage)
-check_language(Fortran)
-if(CMAKE_Fortran_COMPILER)
-  enable_language(Fortran)
-else()
-  set (NOFORTRAN 1)
+if(NOT CMAKE_Fortran_COMPILER)
   if (NOT NO_LAPACK)
      if (NOT XXXXX)
 	message(STATUS "No Fortran compiler found, can build only BLAS and f2c-converted LAPACK")

From 6a05bef0259ea5197ca9c4b9adb3d2ee7c1df1d5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20M=C3=BCtzel?= <markus.muetzel@gmx.de>
Date: Sat, 5 Aug 2023 16:43:25 +0200
Subject: [PATCH 2/4] Disable AVX512 instructions for LLVM Flang before version
 17 or with LLVM Flang on Windows.

---
 CMakeLists.txt | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f3cb0eed4..d35172c96 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -104,6 +104,19 @@ if(NOT NOFORTRAN)
   endif()
 endif()
 
+if (NOT NOFORTRAN AND CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang")
+  if (CMAKE_Fortran_COMPILER_VERSION VERSION_LESS 17 OR WIN32)
+    # The *blas3 tests fail on hardware with AVX512 instruction when using
+    # LLVM Flang before version 17 or when using LLVM Flang on Windows.
+    # Tested with LLVM Flang 16 and LLVM Flang 17 on Windows (MSYS2/CLANG64).
+    # FIXME: Revisit with LLVM Flang 18.
+    if (NOT NO_AVX512)
+      message(STATUS "Disabling AVX512 instructions for LLVM Flang before version 17 or on Windows.")
+    endif()
+    set(NO_AVX512 1)
+  endif()
+endif()
+
 include("${PROJECT_SOURCE_DIR}/cmake/utils.cmake")
 include("${PROJECT_SOURCE_DIR}/cmake/system.cmake")
 

From 3f86013201c9280bf78b52356ceb2f60870ab428 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20M=C3=BCtzel?= <markus.muetzel@gmx.de>
Date: Sat, 5 Aug 2023 16:48:04 +0200
Subject: [PATCH 3/4] CI: Let the build system decide whether or not to build
 with NO_AVX512.

---
 .github/workflows/dynamic_arch.yml | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/.github/workflows/dynamic_arch.yml b/.github/workflows/dynamic_arch.yml
index 4fe6e63fc..85b20c060 100644
--- a/.github/workflows/dynamic_arch.yml
+++ b/.github/workflows/dynamic_arch.yml
@@ -167,9 +167,6 @@ jobs:
             idx: int32
             target-prefix: mingw-w64-clang-x86_64
             fc-pkg: fc
-            # Compiling with Flang 16 seems to cause test errors on machines
-            # with AVX512 instructions. Revisit after MSYS2 distributes Flang 17.
-            no-avx512-flags: -DNO_AVX512=1
           - msystem: CLANG32
             idx: int32
             target-prefix: mingw-w64-clang-i686
@@ -185,9 +182,6 @@ jobs:
             idx64-flags: -DBINARY=64 -DINTERFACE64=1
             target-prefix: mingw-w64-clang-x86_64
             fc-pkg: fc
-            # Compiling with Flang 16 seems to cause test errors on machines
-            # with AVX512 instructions. Revisit after MSYS2 distributes Flang 17.
-            no-avx512-flags: -DNO_AVX512=1
           - msystem: MINGW64
             idx: int32
             target-prefix: mingw-w64-x86_64
@@ -274,7 +268,6 @@ jobs:
                 -DTARGET=CORE2 \
                 ${{ matrix.idx64-flags }} \
                 ${{ matrix.c-lapack-flags }} \
-                ${{ matrix.no-avx512-flags }} \
                 -DCMAKE_C_COMPILER_LAUNCHER=ccache \
                 -DCMAKE_Fortran_COMPILER_LAUNCHER=ccache \
                 ..

From d21c660a99faecfc1244da5cadb1f1bbd7b0f31d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20M=C3=BCtzel?= <markus.muetzel@gmx.de>
Date: Sat, 5 Aug 2023 16:59:34 +0200
Subject: [PATCH 4/4] Don't use OpenMP with LLVM Flang before version 17.

---
 CMakeLists.txt | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d35172c96..57767c598 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -115,6 +115,14 @@ if (NOT NOFORTRAN AND CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang")
     endif()
     set(NO_AVX512 1)
   endif()
+
+  if (CMAKE_Fortran_COMPILER_VERSION VERSION_LESS 17)
+    # LLVM Flang before version 17 doesn't support necessary OpenMP constructs.
+    if (USE_OPENMP)
+      message(STATUS "Disabling OpenMP for LLVM Flang before version 17.")
+      set(USE_OPENMP 0)
+    endif()
+  endif()
 endif()
 
 include("${PROJECT_SOURCE_DIR}/cmake/utils.cmake")