Support parallel builds with make (#491)

Individual COMMANDS in define_custom_command are not guaranteed to
execute sequentially, meaning that the inline headers may be broken if
doing a parallel build with make. Each command is extracted into its
own custom_command (some are merged, such as subsequent sed calls) so
that CMake can properly make sense of the dependencies and generate
consistent headers in parallel.

* Atomise creation of inline header, alias, dispscalar, simd disp, sleefquad header and build
* Reuse existing atomic inline libm header generation for CUDA

Now that custom_commands are atomic, parallel builds should be
supported with make.

* Use CMake cat instead of shell cat

This requires minimum CMake 3.18, which is not particularly
recent. This provides a better cross-platform way of concatenating
files.

CMakeLists.txt

@@ -38,6 +38,24 @@ function(command_arguments PROPNAME)
   set(${PROPNAME} ${quoted_args} PARENT_SCOPE)
 endfunction()
 
+# Helper function for concatenating several files
+function(sleef_concat_files)
+  cmake_parse_arguments(concat_required "" "OUTPUT" "SOURCES" ${ARGN})
+  if("${concat_required_OUTPUT}" STREQUAL "")
+    message(FATAL_ERROR "Must pass OUTPUT to sleef_concat_files")
+  endif()
+
+  if(NOT concat_required_SOURCES)
+    message(FATAL_ERROR "sleef_concat_files not passed any SOURCES")
+  endif()
+
+  add_custom_command(
+    OUTPUT ${concat_required_OUTPUT}
+    COMMAND ${CMAKE_COMMAND} -E cat ${concat_required_SOURCES} > ${concat_required_OUTPUT}
+    DEPENDS ${concat_required_SOURCES}
+    COMMAND_EXPAND_LISTS)
+endfunction()
+
 # Settings
 
 set(SLEEF_ALL_SUPPORTED_EXTENSIONS
@@ -94,7 +112,7 @@ set(COSTOVERRIDE_RVVM2NOFMA 20)
 
 #
 
-cmake_minimum_required(VERSION 3.4.3)
+cmake_minimum_required(VERSION 3.18)
 
 if(${CMAKE_VERSION} VERSION_GREATER "3.14.99")
   cmake_policy(SET CMP0091 NEW)
@@ -318,8 +336,3 @@ if(SLEEF_SHOW_CONFIG)
   endif()
 endif(SLEEF_SHOW_CONFIG)
 
-if (NOT CMAKE_MAKE_PROGRAM MATCHES "ninja")
-  message("")
-  message("*** Note: Parallel build is only supported with Ninja ***")
-  message("")
-endif()

doc/build-with-cmake.md

@@ -17,14 +17,14 @@ Before using CMake you will need to install/build the binaries on your system.
 Most systems have cmake already installed or provided by the standard package
 manager. If that is not the case for you, please
 [download](https://cmake.org/download/) and install now.
-For building SLEEF, version 3.4.3 is the minimum required.
+For building SLEEF, version 3.18 is the minimum required.
 
 # Quick start
 
 1. Make sure cmake is available on the command-line.
 ```
 $ cmake --version
-(should display a version number greater than or equal to 3.4.3)
+(should display a version number greater than or equal to 3.18)
 ```
 
 2. Download the tar from the

doc/html/compile.xhtml

@@ -236,10 +236,6 @@ $ make test
 $ sudo make install</pre>
 </p>
 
-<p>
-  <b style="color:red">Parallel build is only supported with Ninja.</b>
-</p>
-
 <br/>
 
 <p>