Merge pull request #234 from ska-sa/runtime-cpu-features

Add detection of function multi-versioning in the compiler

configure.ac

@@ -155,6 +155,20 @@ SPEAD2_ARG_WITH(
     )]
 )
 
+# -Werror is used to get an error (rather than a warning) if the compiler
+# doesn't support the feature.
+SPEAD2_ARG_WITH(
+    [fmv],
+    [AS_HELP_STRING([--without-fmv], [Do not use compiler function multi-versioning support])],
+    [SPEAD2_USE_FMV],
+    [SPEAD2_CHECK_FEATURE(
+        [fmv], [function multi-versioning], [], [], [],
+        [SPEAD2_USE_FMV=1], [],
+        [__attribute__((target("default"))) void foo() {}],
+        [-Werror]
+    )]
+)
+
 SPEAD2_ARG_WITH(
     [movntdq],
     [AS_HELP_STRING([--without-movntdq], [Do not use MOVNTDQ instruction for non-temporal copies])],
@@ -275,6 +289,7 @@ SPEAD2_PRINT_CONDITION([compiler optimization], [OPTIMIZED])
 SPEAD2_PRINT_CONDITION([link-time optimization], [LTO])
 SPEAD2_PRINT_CONDITION([coverage], [COVERAGE])
 SPEAD2_PRINT_CONDITION([shared library], [SHARED_LIBRARY])
+SPEAD2_PRINT_FEATURE([function multi-versioning], [test "x$SPEAD2_USE_FMV" = "x1"])
 SPEAD2_PRINT_FEATURE([MOVNTDQ instruction], [test "x$SPEAD2_USE_MOVNTDQ" = "x1"])
 echo ""
 echo "System calls:"

include/spead2/common_defines.h

@@ -1,4 +1,4 @@
-/* Copyright 2015, 2020 National Research Foundation (SARAO)
+/* Copyright 2015, 2020, 2023 National Research Foundation (SARAO)
  *
  * This program is free software: you can redistribute it and/or modify it under
  * the terms of the GNU Lesser General Public License as published by the Free
@@ -28,6 +28,7 @@
 #include <utility>
 #include <string>
 #include <functional>
+#include <spead2/common_features.h>
 
 #ifndef SPEAD2_MAX_LOG_LEVEL
 #define SPEAD2_MAX_LOG_LEVEL (spead2::log_level::info)
@@ -43,6 +44,12 @@
 # define SPEAD2_DEPRECATED(msg)
 #endif
 
+#if SPEAD2_USE_FMV
+# define SPEAD2_FMV_TARGET(x) [[gnu::target(x)]]
+#else
+# define SPEAD2_FMV_TARGET(x)
+#endif
+
 /**
  * SPEAD protocol sending and receiving. All SPEAD-64-* flavours are
  * supported.

include/spead2/common_features.h.in

@@ -35,15 +35,30 @@
 #define SPEAD2_USE_SENDMMSG @SPEAD2_USE_SENDMMSG@
 #define SPEAD2_USE_EVENTFD @SPEAD2_USE_EVENTFD@
 #define SPEAD2_USE_PTHREAD_SETAFFINITY_NP @SPEAD2_USE_PTHREAD_SETAFFINITY_NP@
-/* Python on MacOS likes to build universal binaries, so even if it was
- * detected at configure time, it might not be available for a particular
- * build architecture.
+/* Python on MacOS likes to build universal binaries, which causes problems
+ * because it doesn't match the compilation environment detected at
+ * configuration time. So features that we only use on x86 are only enabled
+ * if x86 is actually detected at build time.
  */
 #if defined(__i386__) || defined(__i386) || defined(__x86_64__) || defined(__x86_64)
-# define SPEAD2_USE_MOVNTDQ @SPEAD2_USE_MOVNTDQ@
-#else
+
+# define SPEAD2_USE_FMV @SPEAD2_USE_FMV@
+/* On i386, MOVNTDQ is not guaranteed to exist at runtime, and we need function
+ * multi-versioning to make it safe to use.
+ */
+# if SPEAD2_USE_FMV || defined(__x86_64__) || defined(__x86_64)
+#  define SPEAD2_USE_MOVNTDQ @SPEAD2_USE_MOVNTDQ@
+# else
+#  define SPEAD2_USE_MOVNTDQ 0
+# endif
+
+#else  // not x86
+
+# define SPEAD2_USE_FMV 0
 # define SPEAD2_USE_MOVNTDQ 0
+
 #endif
+
 #define SPEAD2_USE_POSIX_SEMAPHORES @SPEAD2_USE_POSIX_SEMAPHORES@
 #define SPEAD2_USE_PCAP @SPEAD2_USE_PCAP@
 

include/spead2/common_memcpy.h

@@ -19,6 +19,7 @@
 
 #include <cstddef>
 #include <spead2/common_features.h>
+#include <spead2/common_defines.h>
 
 /**
  * Variant of memcpy that uses a non-temporal hint for the destination.
@@ -30,7 +31,15 @@
 namespace spead2
 {
 
+#if SPEAD2_USE_FMV || !SPEAD2_USE_MOVNTDQ
+SPEAD2_FMV_TARGET("default")
 void *memcpy_nontemporal(void * __restrict__ dest, const void * __restrict__ src, std::size_t n) noexcept;
+#endif
+
+#if SPEAD2_USE_MOVNTDQ
+SPEAD2_FMV_TARGET("sse2")
+void *memcpy_nontemporal(void * __restrict__ dest, const void * __restrict__ src, std::size_t n) noexcept;
+#endif
 
 } // namespace spead2
 

src/common_memcpy.cpp

@@ -27,11 +27,18 @@
 namespace spead2
 {
 
+#if SPEAD2_USE_FMV || !SPEAD2_USE_MOVNTDQ
+SPEAD2_FMV_TARGET("default")
 void *memcpy_nontemporal(void * __restrict__ dest, const void * __restrict__ src, std::size_t n) noexcept
 {
-#if !SPEAD2_USE_MOVNTDQ
     return std::memcpy(dest, src, n);
-#else
+}
+#endif // SPEAD2_USE_FMV || !SPEAD2_USE_MOVNTDQ
+
+#if SPEAD2_USE_MOVNTDQ
+SPEAD2_FMV_TARGET("sse2")
+void *memcpy_nontemporal(void * __restrict__ dest, const void * __restrict__ src, std::size_t n) noexcept
+{
     char * __restrict__ dest_c = (char *) dest;
     const char * __restrict__ src_c = (const char *) src;
     // Align the destination to a cache-line boundary
@@ -73,7 +80,7 @@ void *memcpy_nontemporal(void * __restrict__ dest, const void * __restrict__ src
     std::memcpy(dest_c + offset, src_c + offset, tail);
     _mm_sfence();
     return dest;
-#endif // SPEAD2_USE_MOVNTDQ
 }
+#endif // SPEAD2_USE_MOVNTDQ
 
 } // namespace spead2