From 5ff4d77f5585f9aad068fcc473393095e0640ae4 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Wed, 6 Nov 2019 16:54:18 +0100
Subject: [PATCH] Precompile headers

This cuts 'make install -j6' on my laptop from 170s to 134s.
---
 Makefile                  |  4 +--
 configure.ac              |  1 -
 mk/lib.mk                 |  1 +
 mk/patterns.mk            |  4 +--
 mk/precompiled-headers.mk | 42 +++++++++++++++++++++++
 precompiled-headers.h     | 71 +++++++++++++++++++++++++++++++++++++++
 6 files changed, 118 insertions(+), 5 deletions(-)
 create mode 100644 mk/precompiled-headers.mk
 create mode 100644 precompiled-headers.h

diff --git a/Makefile b/Makefile
index 9ac82fda6..c441a933e 100644
--- a/Makefile
+++ b/Makefile
@@ -15,8 +15,8 @@ makefiles = \
   tests/local.mk \
   tests/plugins/local.mk
 
-GLOBAL_CXXFLAGS += -g -Wall -include config.h
-
 -include Makefile.config
 
 include mk/lib.mk
+
+GLOBAL_CXXFLAGS += -g -Wall -include config.h -std=c++17
diff --git a/configure.ac b/configure.ac
index 4a6eaac8a..c67f1e739 100644
--- a/configure.ac
+++ b/configure.ac
@@ -57,7 +57,6 @@ test "$localstatedir" = '${prefix}/var' && localstatedir=/nix/var
 AC_PROG_CC
 AC_PROG_CXX
 AC_PROG_CPP
-AX_CXX_COMPILE_STDCXX_17([noext], [mandatory])
 
 AC_CHECK_TOOL([AR], [ar])
 
diff --git a/mk/lib.mk b/mk/lib.mk
index 1da51d879..b0a36cf8d 100644
--- a/mk/lib.mk
+++ b/mk/lib.mk
@@ -89,6 +89,7 @@ include mk/jars.mk
 include mk/patterns.mk
 include mk/templates.mk
 include mk/tests.mk
+include mk/precompiled-headers.mk
 
 
 # Include all sub-Makefiles.
diff --git a/mk/patterns.mk b/mk/patterns.mk
index 3219d9629..7319f4cdd 100644
--- a/mk/patterns.mk
+++ b/mk/patterns.mk
@@ -1,10 +1,10 @@
 $(buildprefix)%.o: %.cc
 	@mkdir -p "$(dir $@)"
-	$(trace-cxx) $(CXX) -o $@ -c $< $(GLOBAL_CXXFLAGS) $(GLOBAL_CXXFLAGS_PCH) $(CXXFLAGS) $($@_CXXFLAGS) -MMD -MF $(call filename-to-dep, $@) -MP
+	$(trace-cxx) $(CXX) -o $@ -c $< $(GLOBAL_CXXFLAGS_PCH) $(GLOBAL_CXXFLAGS) $(CXXFLAGS) $($@_CXXFLAGS) -MMD -MF $(call filename-to-dep, $@) -MP
 
 $(buildprefix)%.o: %.cpp
 	@mkdir -p "$(dir $@)"
-	$(trace-cxx) $(CXX) -o $@ -c $< $(GLOBAL_CXXFLAGS) $(GLOBAL_CXXFLAGS_PCH) $(CXXFLAGS) $($@_CXXFLAGS) -MMD -MF $(call filename-to-dep, $@) -MP
+	$(trace-cxx) $(CXX) -o $@ -c $< $(GLOBAL_CXXFLAGS_PCH) $(GLOBAL_CXXFLAGS) $(CXXFLAGS) $($@_CXXFLAGS) -MMD -MF $(call filename-to-dep, $@) -MP
 
 $(buildprefix)%.o: %.c
 	@mkdir -p "$(dir $@)"
diff --git a/mk/precompiled-headers.mk b/mk/precompiled-headers.mk
new file mode 100644
index 000000000..779389b26
--- /dev/null
+++ b/mk/precompiled-headers.mk
@@ -0,0 +1,42 @@
+PRECOMPILE_HEADERS ?= 1
+
+print-var-help += \
+  echo "  PRECOMPILE_HEADERS ($(PRECOMPILE_HEADERS)): Whether to use precompiled headers to speed up the build";
+
+GCH = $(buildprefix)precompiled-headers.h.gch
+
+$(GCH): precompiled-headers.h
+	@rm -f $@
+	@mkdir -p "$(dir $@)"
+	$(trace-gen) $(CXX) -x c++-header -o $@ $^ $(GLOBAL_CXXFLAGS)
+
+PCH = $(buildprefix)precompiled-headers.h.pch
+
+$(PCH): precompiled-headers.h
+	@rm -f $@
+	@mkdir -p "$(dir $@)"
+	$(trace-gen) $(CXX) -x c++-header -o $@ $^ $(GLOBAL_CXXFLAGS)
+
+clean-files += $(GCH) $(PCH)
+
+ifeq ($(PRECOMPILE_HEADERS), 1)
+
+  ifeq ($(CXX), g++)
+
+    GLOBAL_CXXFLAGS_PCH += -include $(buildprefix)precompiled-headers.h -Winvalid-pch
+
+    GLOBAL_ORDER_AFTER += $(GCH)
+
+  else ifeq ($(CXX), clang++)
+
+    GLOBAL_CXXFLAGS_PCH += -include-pch $(PCH) -Winvalid-pch
+
+    GLOBAL_ORDER_AFTER += $(PCH)
+
+  else
+
+    $(error Don't know how to precompile headers on $(CXX))
+
+  endif
+
+endif
diff --git a/precompiled-headers.h b/precompiled-headers.h
new file mode 100644
index 000000000..c5790bec4
--- /dev/null
+++ b/precompiled-headers.h
@@ -0,0 +1,71 @@
+#include <algorithm>
+#include <array>
+#include <atomic>
+#include <cassert>
+#include <cctype>
+#include <chrono>
+#include <climits>
+#include <cmath>
+#include <condition_variable>
+#include <cstddef>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <exception>
+#include <functional>
+#include <future>
+#include <iostream>
+#include <limits>
+#include <list>
+#include <locale>
+#include <map>
+#include <memory>
+#include <mutex>
+#include <numeric>
+#include <optional>
+#include <queue>
+#include <random>
+#include <regex>
+#include <set>
+#include <sstream>
+#include <stack>
+#include <stdexcept>
+#include <string>
+#include <thread>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
+
+#include <boost/format.hpp>
+
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <grp.h>
+#include <net/if.h>
+#include <netdb.h>
+#include <netinet/ip.h>
+#include <pwd.h>
+#include <sched.h>
+#include <signal.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/mount.h>
+#include <sys/param.h>
+#include <sys/personality.h>
+#include <sys/resource.h>
+#include <sys/select.h>
+#include <sys/socket.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/syscall.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/utsname.h>
+#include <sys/wait.h>
+#include <termios.h>
+#include <unistd.h>
+
+#include "util.hh"
+#include "args.hh"