diff -r f5c40ab9e233 Makefile.pre.in
--- a/Makefile.pre.in	Tue Aug 18 22:25:16 2015 -0700
+++ b/Makefile.pre.in	Tue Aug 25 18:33:23 2015 +0300
@@ -43,6 +43,10 @@
 HGVERSION=	@HGVERSION@
 HGTAG=		@HGTAG@
 HGBRANCH=	@HGBRANCH@
+PGO_PROF_GEN_FLAG=@PGO_PROF_GEN_FLAG@
+PGO_PROF_USE_FLAG=@PGO_PROF_USE_FLAG@
+LLVM_PROF_MERGER=@LLVM_PROF_MERGER@
+LLVM_PROF_FILE=@LLVM_PROF_FILE@
 
 GNULD=		@GNULD@
 
@@ -226,8 +230,7 @@
 TCLTK_LIBS=	@TCLTK_LIBS@
 
 # The task to run while instrument when building the profile-opt target
-PROFILE_TASK=	$(srcdir)/Tools/pybench/pybench.py -n 2 --with-gc --with-syscheck
-#PROFILE_TASK=	$(srcdir)/Lib/test/regrtest.py
+PROFILE_TASK=$(srcdir)/Lib/test/regrtest.py
 
 # report files for gcov / lcov coverage report
 COVERAGE_INFO=	$(abs_builddir)/coverage.info
@@ -481,23 +484,29 @@
 profile-opt:
 	@echo "Building with support for profile generation:"
 	$(MAKE) clean
+	$(MAKE) profile-removal
 	$(MAKE) build_all_generate_profile
 	@echo "Running benchmark to generate profile data:"
 	$(MAKE) profile-removal
 	$(MAKE) run_profile_task
+	$(MAKE) build_all_merge_profile
 	@echo "Rebuilding with profile guided optimizations:"
 	$(MAKE) clean
 	$(MAKE) build_all_use_profile
+	$(MAKE) profile-removal
 
 build_all_generate_profile:
-	$(MAKE) all CFLAGS_NODIST="$(CFLAGS) -fprofile-generate" LDFLAGS="-fprofile-generate" LIBS="$(LIBS) -lgcov"
+	$(MAKE) all CFLAGS_NODIST="$(CFLAGS) $(PGO_PROF_GEN_FLAG)" LDFLAGS="$(LDFLAGS) $(PGO_PROF_GEN_FLAG)" LIBS="$(LIBS)"
 
 run_profile_task:
 	: # FIXME: can't run for a cross build
-	$(RUNSHARED) ./$(BUILDPYTHON) $(PROFILE_TASK)
+	$(LLVM_PROF_FILE) $(RUNSHARED) ./$(BUILDPYTHON) $(PROFILE_TASK) || true
+
+build_all_merge_profile:
+	$(LLVM_PROF_MERGER)
 
 build_all_use_profile:
-	$(MAKE) all CFLAGS_NODIST="$(CFLAGS) -fprofile-use -fprofile-correction"
+	$(MAKE) all CFLAGS_NODIST="$(CFLAGS) $(PGO_PROF_USE_FLAG)"
 
 # Compile and run with gcov
 .PHONY=coverage coverage-lcov coverage-report
@@ -1568,9 +1577,11 @@
 	-rm -f pybuilddir.txt
 	-rm -f Lib/lib2to3/*Grammar*.pickle
 	-rm -f Programs/_testembed Programs/_freeze_importlib
+	-rm -rf build
 
 profile-removal:
 	find . -name '*.gc??' -exec rm -f {} ';'
+	find . -name '*.profclang?' -exec rm -f {} ';'
 	rm -f $(COVERAGE_INFO)
 	rm -rf $(COVERAGE_REPORT)
 
diff -r f5c40ab9e233 configure.ac
--- a/configure.ac	Tue Aug 18 22:25:16 2015 -0700
+++ b/configure.ac	Tue Aug 25 18:33:23 2015 +0300
@@ -1218,6 +1218,29 @@
 fi],
 [AC_MSG_RESULT(no)])
 
+# enable PGO flags
+AC_SUBST(PGO_PROF_GEN_FLAG)
+AC_SUBST(PGO_PROF_USE_FLAG)
+AC_SUBST(LLVM_PROF_MERGER)
+AC_SUBST(LLVM_PROF_FILE)
+if test "$GCC" = "yes"
+then
+  case $ac_sys_system in	
+    Darwin*)
+      PGO_PROF_GEN_FLAG="-fprofile-instr-generate"
+      PGO_PROF_USE_FLAG="-fprofile-instr-use=code.profclangd"
+      LLVM_PROF_MERGER="llvm-profdata merge -output=code.profclangd *.profclangr"
+      LLVM_PROF_FILE="LLVM_PROFILE_FILE=\"code-%p.profclangr\""
+      ;;
+    *)
+      PGO_PROF_GEN_FLAG="-fprofile-generate"
+      PGO_PROF_USE_FLAG="-fprofile-use -fprofile-correction"
+      LLVM_PROF_MERGER="true"
+      LLVM_PROF_FILE=""
+      ;;
+  esac
+fi
+
 # XXX Shouldn't the code above that fiddles with BASECFLAGS and OPT be
 # merged with this chunk of code?