From 774407078728faee465addc48f825a7da330d40a Mon Sep 17 00:00:00 2001
From: Christoph Junghans <junghans@lanl.gov>
Date: Tue, 10 Mar 2020 09:08:10 -0600
Subject: gromacs: remove simd variants (#13636)

---
 .../repos/builtin/packages/gromacs/package.py      | 48 +++++++++++++++-------
 1 file changed, 34 insertions(+), 14 deletions(-)

(limited to 'var')

diff --git a/var/spack/repos/builtin/packages/gromacs/package.py b/var/spack/repos/builtin/packages/gromacs/package.py
index 72aca3e5f0..037b25721b 100644
--- a/var/spack/repos/builtin/packages/gromacs/package.py
+++ b/var/spack/repos/builtin/packages/gromacs/package.py
@@ -2,8 +2,7 @@
 # Spack Project Developers. See the top-level COPYRIGHT file for details.
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
-
-from spack import *
+import llnl.util.cpu
 
 
 class Gromacs(CMakePackage):
@@ -62,12 +61,6 @@ class Gromacs(CMakePackage):
             description='The build type to build',
             values=('Debug', 'Release', 'RelWithDebInfo', 'MinSizeRel',
                     'Reference', 'RelWithAssert', 'Profile'))
-    variant('simd', default='auto',
-            description='The SIMD instruction set to use',
-            values=('auto', 'none', 'SSE2', 'SSE4.1', 'AVX_128_FMA', 'AVX_256',
-                    'AVX2_128', 'AVX2_256', 'AVX_512', 'AVX_512_KNL',
-                    'IBM_QPX', 'Sparc64_HPC_ACE', 'IBM_VMX', 'IBM_VSX',
-                    'ARM_NEON', 'ARM_NEON_ASIMD'))
     variant('rdtscp', default=True, description='Enable RDTSCP instruction usage')
     variant('mdrun_only', default=False,
             description='Enables the build of a cut-down version'
@@ -119,13 +112,40 @@ class Gromacs(CMakePackage):
         else:
             options.append('-DGMX_GPU:BOOL=OFF')
 
-        simd_value = self.spec.variants['simd'].value
-        if simd_value == 'auto':
-            pass
-        elif simd_value == 'none':
-            options.append('-DGMX_SIMD:STRING=None')
+        # Activate SIMD based on properties of the target
+        target = self.spec.target
+        if target >= llnl.util.cpu.targets['bulldozer']:
+            # AMD Family 15h
+            options.append('-DGMX_SIMD=AVX_128_FMA')
+        elif target >= llnl.util.cpu.targets['zen']:
+            # AMD Family 17h
+            options.append('-DGMX_SIMD=AVX2_128')
+        elif target >= llnl.util.cpu.targets['power7']:
+            # IBM Power 7 and beyond
+            options.append('-DGMX_SIMD=IBM_VSX')
+        elif target.family == llnl.util.cpu.targets['aarch64']:
+            # ARMv8
+            options.append('-DGMX_SIMD=ARM_NEON_ASIMD')
+        elif target == llnl.util.cpu.targets['mic_knl']:
+            # Intel KNL
+            options.append('-DGMX_SIMD=AVX_512_KNL')
+        elif target.vendor == 'GenuineIntel':
+            # Other Intel architectures
+            simd_features = [
+                ('sse2', 'SSE2'),
+                ('sse4_1', 'SSE4.1'),
+                ('avx', 'AVX_256'),
+                ('axv128', 'AVX2_128'),
+                ('avx2', 'AVX2_256'),
+                ('avx512', 'AVX_512'),
+            ]
+            for feature, flag in reversed(simd_features):
+                if feature in target:
+                    options.append('-DGMX_SIMD:STRING={0}'.format(flag))
+                    break
         else:
-            options.append('-DGMX_SIMD:STRING=' + simd_value)
+            # Fall back to this for unknown microarchitectures
+            options.append('-DGMX_SIMD:STRING=None')
 
         if '-rdtscp' in self.spec:
             options.append('-DGMX_USE_RDTSCP:BOOL=OFF')
-- 
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