diff -r c49ff8dbf907 Makefile.pre.in
--- a/Makefile.pre.in	Wed Sep 07 01:21:14 2016 +0200
+++ b/Makefile.pre.in	Tue Sep 06 17:01:22 2016 -0700
@@ -459,7 +459,7 @@
 # Rules
 
 # Default target
-all:		build_all
+all:		@DEF_MAKE_ALL_RULE@
 build_all:	$(BUILDPYTHON) oldsharedmods sharedmods gdbhooks Programs/_testembed python-config
 
 # Compile a binary with profile guided optimization.
@@ -483,7 +483,7 @@
 	$(MAKE) profile-removal
 
 build_all_generate_profile:
-	$(MAKE) all CFLAGS_NODIST="$(CFLAGS) $(PGO_PROF_GEN_FLAG) @LTOFLAGS@" LDFLAGS="$(LDFLAGS) $(PGO_PROF_GEN_FLAG) @LTOFLAGS@" LIBS="$(LIBS)"
+	$(MAKE) @DEF_MAKE_RULE@ CFLAGS_NODIST="$(CFLAGS) $(PGO_PROF_GEN_FLAG) @LTOFLAGS@" LDFLAGS="$(LDFLAGS) $(PGO_PROF_GEN_FLAG) @LTOFLAGS@" LIBS="$(LIBS)"
 
 run_profile_task:
 	: # FIXME: can't run for a cross build
@@ -493,14 +493,14 @@
 	$(LLVM_PROF_MERGER)
 
 build_all_use_profile:
-	$(MAKE) all CFLAGS_NODIST="$(CFLAGS) $(PGO_PROF_USE_FLAG) @LTOFLAGS@" LDFLAGS="$(LDFLAGS) @LTOFLAGS@"
+	$(MAKE) @DEF_MAKE_RULE@ CFLAGS_NODIST="$(CFLAGS) $(PGO_PROF_USE_FLAG) @LTOFLAGS@" LDFLAGS="$(LDFLAGS) @LTOFLAGS@"
 
 # Compile and run with gcov
 .PHONY=coverage coverage-lcov coverage-report
 coverage:
 	@echo "Building with support for coverage checking:"
 	$(MAKE) clean profile-removal
-	$(MAKE) all CFLAGS="$(CFLAGS) -O0 -pg -fprofile-arcs -ftest-coverage" LIBS="$(LIBS) -lgcov"
+	$(MAKE) @DEF_MAKE_RULE@ CFLAGS="$(CFLAGS) -O0 -pg -fprofile-arcs -ftest-coverage" LIBS="$(LIBS) -lgcov"
 
 coverage-lcov:
 	@echo "Creating Coverage HTML report with LCOV:"
diff -r c49ff8dbf907 configure.ac
--- a/configure.ac	Wed Sep 07 01:21:14 2016 +0200
+++ b/configure.ac	Tue Sep 06 17:01:22 2016 -0700
@@ -1282,6 +1282,37 @@
 fi],
 [AC_MSG_RESULT(no)])
 
+# Enable optimization flags
+AC_SUBST(DEF_MAKE_ALL_RULE)
+AC_SUBST(DEF_MAKE_RULE)
+Py_OPT='false'
+AC_MSG_CHECKING(for --with-optimizations)
+AC_ARG_WITH(optimizations, AS_HELP_STRING([--with-optimizations], [Enable all optimizations  when available (LTO, PGO, etc). Disabled by default.]),
+[
+if test "$withval" != no
+then
+  Py_OPT='true'
+  AC_MSG_RESULT(yes);
+else
+  Py_OPT='false'
+  AC_MSG_RESULT(no);
+fi],
+[AC_MSG_RESULT(no)])
+if test "$Py_OPT" = 'true' ; then
+  Py_LTO='true'
+  case $ac_sys_system in
+    Darwin*)
+      # At least on macOS El Capitan, LTO does not work with PGO.
+      Py_LTO='false'
+      ;;
+    esac
+  DEF_MAKE_ALL_RULE="profile-opt"
+  DEF_MAKE_RULE="build_all"
+else
+  DEF_MAKE_ALL_RULE="build_all"
+  DEF_MAKE_RULE="all"
+fi
+
 # Enable LTO flags
 AC_SUBST(LTOFLAGS)
 AC_MSG_CHECKING(for --with-lto)
@@ -5337,3 +5368,13 @@
 			-s Modules Modules/Setup.config \
 			Modules/Setup.local Modules/Setup
 mv config.c Modules
+
+if test "$Py_OPT" = 'false' -a "$Py_DEBUG" != 'true'; then
+    echo "" >&AS_MESSAGE_FD
+    echo "" >&AS_MESSAGE_FD
+    echo "If you want a release build with all optimizations active (LTO, PGO, etc),"
+    echo "please run ./configure --with-optimizations" >&AS_MESSAGE_FD
+    echo "" >&AS_MESSAGE_FD
+    echo "" >&AS_MESSAGE_FD
+fi
+