QLibrary: find AVX2 (Haswell) optimized plugins and libraries

Libraries are placed in a subdir "haswell/" of the main library dir,
whereas plugins are simply named with ".avx2" appended to the plugin
name (plugin.so.avx2). The "haswell/" library directory suffix is a
convention found in glibc since version 2.26, whereas the ".avx2" and
".avx512" suffixes are a convention found in the Clear Linux OS for
Intel Architecture.

This patch implements this for all Unix OSes, except for Darwin, where
the fat file format already has a sub-architecture for Haswell
(x86_64h).

We could also implement the "sse2/" subdir search for libraries, but I
don't think it's worth the cost in 2018.

Change-Id: Iff4151c519c144d580c4fffd1539fe5ee9a4d7b1
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/src/corelib/plugin/qlibrary_unix.cpp b/src/corelib/plugin/qlibrary_unix.cpp
index 23b9ad6434..7ffd1369b9 100644
--- a/src/corelib/plugin/qlibrary_unix.cpp
+++ b/src/corelib/plugin/qlibrary_unix.cpp
@@ -1,6 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2018 Intel Corporation
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -43,6 +44,7 @@
 #include "qlibrary_p.h"
 #include <qcoreapplication.h>
 #include <private/qfilesystementry_p.h>
+#include <private/qsimd_p.h>
 
 #include <dlfcn.h>
 
@@ -178,6 +180,27 @@ bool QLibraryPrivate::load_sys()
         prefixes.append(QString());
     }
 
+#if defined(Q_PROCESSOR_X86) && !defined(Q_OS_DARWIN)
+    if (qCpuHasFeature(ArchHaswell)) {
+        auto transform = [](QStringList &list, QString (*f)(QString)) {
+            QStringList tmp;
+            qSwap(tmp, list);
+            list.reserve(tmp.size() * 2);
+            for (const QString &s : qAsConst(tmp)) {
+                list.append(f(s));
+                list.append(s);
+            }
+        };
+        if (pluginState == IsAPlugin) {
+            // add ".avx2" to each suffix in the list
+            transform(suffixes, [](QString s) { return s.append(QLatin1String(".avx2")); });
+        } else {
+            // prepend "haswell/" to each prefix in the list
+            transform(prefixes, [](QString s) { return s.prepend(QLatin1String("haswell/")); });
+        }
+    }
+#endif
+
     bool retry = true;
     for(int prefix = 0; retry && !pHnd && prefix < prefixes.size(); prefix++) {
         for(int suffix = 0; retry && !pHnd && suffix < suffixes.size(); suffix++) {