From ab349fffa9a849a4ad78fb05760cd1b3fe58ac01 Mon Sep 17 00:00:00 2001
From: Matthew Thompson <matthew.thompson@nasa.gov>
Date: Fri, 19 Jan 2024 09:22:58 -0500
Subject: [PATCH] Add Hygon support for Intel Fortran

---
 CHANGELOG.md                           |  2 ++
 compiler/flags/IntelLLVM_Fortran.cmake | 11 +++++++++++
 compiler/flags/Intel_Fortran.cmake     |  8 ++++++++
 3 files changed, 21 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index fde51bb8..574b0cdc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- Added support for Hygon processors with Intel Fortran
+
 ### Changed
 
 ### Deprecated
diff --git a/compiler/flags/IntelLLVM_Fortran.cmake b/compiler/flags/IntelLLVM_Fortran.cmake
index 0d26fe8e..6549292a 100644
--- a/compiler/flags/IntelLLVM_Fortran.cmake
+++ b/compiler/flags/IntelLLVM_Fortran.cmake
@@ -63,12 +63,23 @@ set (NO_RANGE_CHECK "")
 
 cmake_host_system_information(RESULT proc_description QUERY PROCESSOR_DESCRIPTION)
 if (${proc_description} MATCHES "EPYC")
+  # AMD EPYC processors support AVX2, but only via the -march=core-avx2 flag
+  set (COREAVX2_FLAG "-march=core-avx2")
+elseif (${proc_description} MATCHES "Hygon")
+  # Hygon processors support AVX2, but only via the -march=core-avx2 flag
   set (COREAVX2_FLAG "-march=core-avx2")
 elseif (${proc_description} MATCHES "Intel")
+  # All the Intel processors that GEOS runs on support AVX2, but to be
+  # consistent with the AMD processors, we use the -march=core-avx2 flag
   set (COREAVX2_FLAG "-march=core-avx2")
   # Previous versions of GEOS used this flag, which was not portable
   # for AMD. Keeping here for a few versions for historical purposes.
   #set (COREAVX2_FLAG "-xCORE-AVX2")
+elseif ( ${CMAKE_HOST_SYSTEM_PROCESSOR} STREQUAL "x86_64" )
+  # This is a fallback for when the above doesn't work. It should work
+  # for most x86_64 processors, but it is not guaranteed to be optimal.
+  message(WARNING "Unknown processory type. Defaulting to a generic x86_64 processor. Performance may be suboptimal.")
+  set (COREAVX2_FLAG "")
 else ()
   message(FATAL_ERROR "Unknown processor. Please file an issue at https://github.com/GEOS-ESM/ESMA_cmake")
 endif ()
diff --git a/compiler/flags/Intel_Fortran.cmake b/compiler/flags/Intel_Fortran.cmake
index 3214e1d2..a5368e00 100644
--- a/compiler/flags/Intel_Fortran.cmake
+++ b/compiler/flags/Intel_Fortran.cmake
@@ -69,13 +69,21 @@ set (NO_RANGE_CHECK "")
 
 cmake_host_system_information(RESULT proc_description QUERY PROCESSOR_DESCRIPTION)
 if (${proc_description} MATCHES "EPYC")
+  # AMD EPYC processors support AVX2, but only via the -march=core-avx2 flag
+  set (COREAVX2_FLAG "-march=core-avx2")
+elseif (${proc_description} MATCHES "Hygon")
+  # Hygon processors support AVX2, but only via the -march=core-avx2 flag
   set (COREAVX2_FLAG "-march=core-avx2")
 elseif (${proc_description} MATCHES "Intel")
+  # All the Intel processors that GEOS runs on support AVX2, but to be
+  # consistent with the AMD processors, we use the -march=core-avx2 flag
   set (COREAVX2_FLAG "-march=core-avx2")
   # Previous versions of GEOS used this flag, which was not portable
   # for AMD. Keeping here for a few versions for historical purposes.
   #set (COREAVX2_FLAG "-xCORE-AVX2")
 elseif ( ${CMAKE_HOST_SYSTEM_PROCESSOR} STREQUAL "x86_64" )
+  # This is a fallback for when the above doesn't work. It should work
+  # for most x86_64 processors, but it is not guaranteed to be optimal.
   message(WARNING "Unknown processory type. Defaulting to a generic x86_64 processor. Performance may be suboptimal.")
   set (COREAVX2_FLAG "")
   # Once you are in here, you are probably on Rosetta, but not required.