gh-xxxx: move BOLT arguments to configure

This allows easily customizing the arguments to `llvm-bolt` without
having to edit the Makefile.

Arguments can be passed to configure and are reflected in configure
output, which can be useful for log analysis.

When defined in the Makefile we use `?=` syntax so the flags can be
overridden via `make VAR=VALUE` syntax or via environment variables.
Super useful for iterating on different BOLT flags.

Author: indygreg

Makefile.pre.in

@@ -724,6 +724,9 @@ profile-pgo-apply-stamp: profile-pgo-analyze-stamp
 # List of binaries that BOLT runs on.
 BOLT_BINARIES = $(BUILDPYTHON)
 
+BOLT_INSTRUMENT_FLAGS ?= @BOLT_INSTRUMENT_FLAGS@
+BOLT_APPLY_FLAGS ?= @BOLT_APPLY_FLAGS@
+
 # Remove traces of bolt.
 .PHONY: clean-bolt
 clean-bolt:
@@ -757,7 +760,7 @@ profile-bolt-instrument-stamp: profile-bolt-prebuild-stamp
 	done
 	# Ensure prior BOLT state is purged.
 	$(MAKE) clean-bolt
-	@LLVM_BOLT@ ./$(BUILDPYTHON) -instrument -instrumentation-file-append-pid -instrumentation-file=$(abspath $(BUILDPYTHON).bolt) -o $(BUILDPYTHON).bolt_inst
+	@LLVM_BOLT@ ./$(BUILDPYTHON) -instrument -instrumentation-file-append-pid -instrumentation-file=$(abspath $(BUILDPYTHON).bolt) -o $(BUILDPYTHON).bolt_inst $(BOLT_INSTRUMENT_FLAGS)
 	touch $@
 
 profile-bolt-run-stamp: profile-bolt-instrument-stamp
@@ -769,7 +772,7 @@ profile-bolt-analyze-stamp: profile-bolt-run-stamp
 	touch $@
 
 profile-bolt-apply-stamp: profile-bolt-analyze-stamp
-	@LLVM_BOLT@ ./$(BUILDPYTHON) -o $(BUILDPYTHON).bolt -data=$(BUILDPYTHON).fdata -update-debug-sections -reorder-blocks=ext-tsp -reorder-functions=hfsort+ -split-functions=3 -icf=1 -inline-all -split-eh -reorder-functions-use-hot-size -peepholes=all -jump-tables=aggressive -inline-ap -indirect-call-promotion=all -dyno-stats -use-gnu-stack -frame-opt=hot
+	@LLVM_BOLT@ ./$(BUILDPYTHON) -o $(BUILDPYTHON).bolt -data=$(BUILDPYTHON).fdata $(BOLT_APPLY_FLAGS)
 	mv $(BUILDPYTHON) $(BUILDPYTHON).prebolt
 	mv $(BUILDPYTHON).bolt $(BUILDPYTHON)
 	touch $@

configure

@@ -2083,6 +2083,22 @@ if test "$Py_BOLT" = 'true' ; then
   fi
 fi
 
+AC_ARG_VAR(BOLT_INSTRUMENT_FLAGS, Arguments to llvm-bolt when instrumenting binaries)
+AC_MSG_CHECKING(BOLT_INSTRUMENT_FLAGS)
+if test -z "${BOLT_INSTRUMENT_FLAGS}"
+then
+    BOLT_INSTRUMENT_FLAGS=
+fi
+AC_MSG_RESULT($BOLT_INSTRUMENT_FLAGS)
+
+AC_ARG_VAR(BOLT_APPLY_FLAGS, Arguments to llvm-bolt when creating a BOLT optimized binary)
+AC_MSG_CHECKING(BOLT_APPLY_FLAGS)
+if test -z "${BOLT_APPLY_FLAGS}"
+then
+    BOLT_APPLY_FLAGS="-update-debug-sections -reorder-blocks=ext-tsp -reorder-functions=hfsort+ -split-functions=3 -icf=1 -inline-all -split-eh -reorder-functions-use-hot-size -peepholes=all -jump-tables=aggressive -inline-ap -indirect-call-promotion=all -dyno-stats -use-gnu-stack -frame-opt=hot"
+fi
+AC_MSG_RESULT($BOLT_APPLY_FLAGS)
+
 # XXX Shouldn't the code above that fiddles with BASECFLAGS and OPT be
 # merged with this chunk of code?