diff --git a/.gitignore b/.gitignore
index d9c4a7972f076d..547e6746e1d91b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -122,8 +122,7 @@ Tools/unicode/data/
 # hendrikmuhs/ccache-action@v1
 /.ccache
 /platform
-/profile-clean-stamp
-/profile-run-stamp
+/profile-*-stamp
 /Python/deepfreeze/*.c
 /pybuilddir.txt
 /pyconfig.h
diff --git a/Makefile.pre.in b/Makefile.pre.in
index 7c44b7be5dbe67..3d2386a62e0092 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -601,13 +601,27 @@ LIBHACL_SHA2_HEADERS= \
 #########################################################################
 # Rules
 
-# Default target
-all:		@DEF_MAKE_ALL_RULE@
+# Default target.
+# Likely either `build-plain` or `build-optimized`.
+all: @MAKE_TARGET_ALL@
 
 # First target in Makefile is implicit default. So .PHONY needs to come after
 # all.
 .PHONY: all
 
+# Build without any optimizations or instrumented binaries.
+.PHONY: build-plain
+build-plain: @MAKE_TARGET_BUILD_PLAIN@
+
+# Build with optimizations (PGO, BOLT, etc).
+.PHONY: build-optimized
+build-optimized: @MAKE_TARGET_BUILD_OPTIMIZED@
+
+.PHONY: build-optimized-not-enabled
+build-optimized-not-enabled:
+	@echo "build-optimized requires --enable-optimizations in configure; aborting"
+	@exit 1
+
 .PHONY: build_all
 build_all:	check-clean-src $(BUILDPYTHON) platform sharedmods \
 		gdbhooks Programs/_testembed scripts checksharedmods rundsymutil
@@ -629,81 +643,154 @@ check-clean-src:
 		exit 1; \
 	fi
 
-# Profile generation build must start from a clean tree.
+# Profile-based optimization.
+#
+# PGO and BOLT profile-based optimization is supported. For each optimization,
+# roughly the following steps are done:
+#
+# 1. "Instrument" binaries with run-time data collection (e.g. build or modify
+#    a variant of the binary.)
+# 2. "Run" instrumented binaries (via subset of test suite) to collect data.
+# 3. "Analyze" / collect / merge data files from previous step.
+# 4. "Apply" collected data from above. (e.g. rebuild or modify a binary).
+#
+# 0, 1, or multiple profile based optimizations can be enabled.
+#
+# We track the progress of profile-based optimization using various "stamp"
+# files. An empty stamp file tracks the stage of optimization we're in.
+# Each *-stamp rule that follows is defined in execution / dependency order.
+
+# Remove files produced by or used for tracking profile-guided optimization.
+.PHONY: profile-remove
+profile-remove: clean-bolt
+	find . -name '*.gc??' -exec rm -f {} ';'
+	find . -name '*.profclang?' -exec rm -f {} ';'
+	find . -name '*.dyn' -exec rm -f {} ';'
+	rm -f $(COVERAGE_INFO)
+	rm -rf $(COVERAGE_REPORT)
+	# Remove all progress tracking stamps to ensure a clean slate.
+	rm -f profile-*-stamp
+
+# Profile-based optimization requires a fresh build environment.
 profile-clean-stamp:
-	$(MAKE) clean
+	$(MAKE) clean profile-remove
 	touch $@
 
-# Compile with profile generation enabled.
-profile-gen-stamp: profile-clean-stamp
+# Build with PGO instrumentation enabled.
+profile-pgo-instrument-stamp: profile-clean-stamp
 	@if [ $(LLVM_PROF_ERR) = yes ]; then \
 		echo "Error: Cannot perform PGO build because llvm-profdata was not found in PATH" ;\
 		echo "Please add it to PATH and run ./configure again" ;\
 		exit 1;\
 	fi
 	@echo "Building with support for profile generation:"
-	$(MAKE) build_all_generate_profile
+	$(MAKE) @MAKE_TARGET_BUILD_PLAIN@ CFLAGS_NODIST="$(CFLAGS_NODIST) $(PGO_PROF_GEN_FLAG)" LDFLAGS_NODIST="$(LDFLAGS_NODIST) $(PGO_PROF_GEN_FLAG)" LIBS="$(LIBS)"
 	touch $@
 
-# Run task with profile generation build to create profile information.
-profile-run-stamp:
+# Run PGO instrumented binaries and collect profile data.
+profile-pgo-run-stamp: profile-pgo-instrument-stamp
 	@echo "Running code to generate profile data (this can take a while):"
-	# First, we need to create a clean build with profile generation
-	# enabled.
-	$(MAKE) profile-gen-stamp
-	# Next, run the profile task to generate the profile information.
-	$(MAKE) run_profile_task
-	$(MAKE) build_all_merge_profile
-	# Remove profile generation binary since we are done with it.
-	$(MAKE) clean-retain-profile
-	# This is an expensive target to build and it does not have proper
-	# makefile dependency information.  So, we create a "stamp" file
-	# to record its completion and avoid re-running it.
-	touch $@
-
-.PHONY: build_all_generate_profile
-build_all_generate_profile:
-	$(MAKE) @DEF_MAKE_RULE@ CFLAGS_NODIST="$(CFLAGS_NODIST) $(PGO_PROF_GEN_FLAG)" LDFLAGS_NODIST="$(LDFLAGS_NODIST) $(PGO_PROF_GEN_FLAG)" LIBS="$(LIBS)"
-
-.PHONY: run_profile_task
-run_profile_task:
 	@ # FIXME: can't run for a cross build
 	$(LLVM_PROF_FILE) $(RUNSHARED) ./$(BUILDPYTHON) $(PROFILE_TASK) || true
+	touch $@
 
-.PHONY: build_all_merge_profile
-build_all_merge_profile:
+# Collect data files produced by running PGO instrumented binaries.
+profile-pgo-analyze-stamp: profile-pgo-run-stamp
 	$(LLVM_PROF_MERGER)
+	# Remove profile generation binary since we are done with it.
+	$(MAKE) clean-retain-profile
+	touch $@
 
-# Compile Python binary with profile guided optimization.
-# To force re-running of the profile task, remove the profile-run-stamp file.
-.PHONY: profile-opt
-profile-opt: profile-run-stamp
+# Use collected PGO data to influence rebuild of binaries.
+profile-pgo-apply-stamp: profile-pgo-analyze-stamp
 	@echo "Rebuilding with profile guided optimizations:"
-	-rm -f profile-clean-stamp
-	$(MAKE) @DEF_MAKE_RULE@ CFLAGS_NODIST="$(CFLAGS_NODIST) $(PGO_PROF_USE_FLAG)" LDFLAGS_NODIST="$(LDFLAGS_NODIST)"
-
-.PHONY: bolt-opt
-bolt-opt: @PREBOLT_RULE@
-	rm -f *.fdata
-	@if $(READELF) -p .note.bolt_info $(BUILDPYTHON) | grep BOLT > /dev/null; then\
-		echo "skip: $(BUILDPYTHON) is already BOLTed."; \
-	else \
-		@LLVM_BOLT@ ./$(BUILDPYTHON) -instrument -instrumentation-file-append-pid -instrumentation-file=$(abspath $(BUILDPYTHON).bolt) -o $(BUILDPYTHON).bolt_inst; \
-		./$(BUILDPYTHON).bolt_inst $(PROFILE_TASK) || true; \
-		@MERGE_FDATA@ $(BUILDPYTHON).*.fdata > $(BUILDPYTHON).fdata; \
-		@LLVM_BOLT@ ./$(BUILDPYTHON) -o $(BUILDPYTHON).bolt -data=$(BUILDPYTHON).fdata -update-debug-sections -reorder-blocks=ext-tsp -reorder-functions=hfsort+ -split-functions -icf=1 -inline-all -split-eh -reorder-functions-use-hot-size -peepholes=none -jump-tables=aggressive -inline-ap -indirect-call-promotion=all -dyno-stats -use-gnu-stack -frame-opt=hot; \
-		rm -f *.fdata; \
-		rm -f $(BUILDPYTHON).bolt_inst; \
-		mv $(BUILDPYTHON).bolt $(BUILDPYTHON); \
+	# Need to purge PGO instrumented build to force a rebuild.
+	$(MAKE) clean-retain-profile
+	$(MAKE) @MAKE_TARGET_BUILD_PLAIN@ CFLAGS_NODIST="$(CFLAGS_NODIST) $(PGO_PROF_USE_FLAG)" LDFLAGS_NODIST="$(LDFLAGS_NODIST)"
+	touch $@
+
+# BOLT supports instrumenting and applying changes to standalone binaries
+# without having to recompile.
+#
+# BOLT can run independently or in addition to PGO. If running with PGO,
+# it always runs after PGO. Care needs to be taken to preserve PGO state
+# when running BOLT so make doesn't re-apply PGO.
+#
+# BOLT also can't instrument binaries that have already had BOLT applied
+# to them. So we make an attempt to preserve and re-use the pristine
+# pre-BOLT binaries so developers can iterate on just BOLT optimization
+# passes.
+
+# List of binaries that BOLT runs on.
+BOLT_BINARIES = @BOLT_BINARIES@
+
+BOLT_INSTRUMENT_FLAGS ?= @BOLT_INSTRUMENT_FLAGS@
+BOLT_APPLY_FLAGS ?= @BOLT_APPLY_FLAGS@
+
+# Remove traces of bolt.
+.PHONY: clean-bolt
+clean-bolt:
+	# Instrumented binaries.
+	find . -name '*.bolt_inst' -exec rm -f {} ';'
+	# The data files they produce.
+	find . -name '*.fdata' -exec rm -f {} ';'
+
+# BOLTs dependencies are a bit wonky.
+#
+# If PGO is enabled, we can take a native rule dependency on a stamp file.
+# If PGO isn't enabled, we don't have a stamp to key off of and the phony
+# target (e.g. build_all) will always force rebuilds. So we call out to
+# make externally to sidestep the dependency.
+#
+# We can simplify this hack if we ever get stamp files for plain builds.
+profile-bolt-prebuild-stamp: @MAKE_BOLT_NATIVE_DEPENDENCY@
+	if [ -n "@MAKE_BOLT_MAKE_DEPENDENCY@" ]; then \
+	    $(MAKE) @MAKE_BOLT_MAKE_DEPENDENCY@; \
 	fi
+	touch $@
 
+profile-bolt-instrument-stamp: profile-bolt-prebuild-stamp
+	for bin in $(BOLT_BINARIES); do \
+	    prebolt="$${bin}.prebolt"; \
+	    if [ -e "$${prebolt}" ]; then \
+	        echo "Restoring pre-BOLT binary $${prebolt}"; \
+	        mv "$${bin}.prebolt" "$${bin}"; \
+	    fi; \
+	    cp "$${bin}" "$${prebolt}"; \
+	done
+	# Ensure prior BOLT state is purged.
+	$(MAKE) clean-bolt
+	for bin in $(BOLT_BINARIES); do \
+	    @LLVM_BOLT@ $${bin} -instrument -instrumentation-file-append-pid -instrumentation-file=$(abspath $${bin}.bolt) -o $${bin}.bolt_inst $(BOLT_INSTRUMENT_FLAGS); \
+	    mv "$${bin}.bolt_inst" "$${bin}"; \
+    done
+	touch $@
+
+profile-bolt-run-stamp: profile-bolt-instrument-stamp
+	$(RUNSHARED) ./$(BUILDPYTHON) $(PROFILE_TASK) || true
+	touch $@
+
+profile-bolt-analyze-stamp: profile-bolt-run-stamp
+	for bin in $(BOLT_BINARIES); do \
+	    @MERGE_FDATA@ $${bin}.*.fdata > $${bin}.fdata; \
+	done
+	touch $@
+
+profile-bolt-apply-stamp: profile-bolt-analyze-stamp
+	for bin in $(BOLT_BINARIES); do \
+	    @LLVM_BOLT@ "$${bin}.prebolt" -o "$${bin}.bolt" -data="$${bin}.fdata" $(BOLT_APPLY_FLAGS); \
+	    mv "$${bin}.bolt" "$${bin}"; \
+	done
+	touch $@
+
+# End of profile-based optimization rules.
 
 # Compile and run with gcov
 .PHONY: coverage
 coverage:
 	@echo "Building with support for coverage checking:"
 	$(MAKE) clean
-	$(MAKE) @DEF_MAKE_RULE@ CFLAGS="$(CFLAGS) -O0 -pg --coverage" LDFLAGS="$(LDFLAGS) --coverage"
+	$(MAKE) @MAKE_SIMPLE_BUILD_TARGET@ CFLAGS="$(CFLAGS) -O0 -pg --coverage" LDFLAGS="$(LDFLAGS) --coverage"
 
 .PHONY: coverage-lcov
 coverage-lcov:
@@ -2622,23 +2709,9 @@ clean-retain-profile: pycremoval
 	-rm -f Python/frozen_modules/MANIFEST
 	-find build -type f -a ! -name '*.gc??' -exec rm -f {} ';'
 	-rm -f Include/pydtrace_probes.h
-	-rm -f profile-gen-stamp
-
-.PHONY: profile-removal
-profile-removal:
-	find . -name '*.gc??' -exec rm -f {} ';'
-	find . -name '*.profclang?' -exec rm -f {} ';'
-	find . -name '*.dyn' -exec rm -f {} ';'
-	rm -f $(COVERAGE_INFO)
-	rm -rf $(COVERAGE_REPORT)
-	rm -f profile-run-stamp
 
 .PHONY: clean
 clean: clean-retain-profile
-	@if test @DEF_MAKE_ALL_RULE@ = profile-opt; then \
-		rm -f profile-gen-stamp profile-clean-stamp; \
-		$(MAKE) profile-removal; \
-	fi
 
 .PHONY: clobber
 clobber: clean
diff --git a/configure b/configure
index 7aad4fe89e3cbf..b2cd8c24a4f0c4 100755
--- a/configure
+++ b/configure
@@ -883,11 +883,15 @@ CFLAGS_NODIST
 BASECFLAGS
 CFLAGS_ALIASING
 OPT
+BOLT_APPLY_FLAGS
+BOLT_INSTRUMENT_FLAGS
+BOLT_BINARIES
 MERGE_FDATA
 LLVM_BOLT
 ac_ct_READELF
 READELF
-PREBOLT_RULE
+MAKE_BOLT_MAKE_DEPENDENCY
+MAKE_BOLT_NATIVE_DEPENDENCY
 LLVM_PROF_FOUND
 LLVM_PROFDATA
 LLVM_PROF_ERR
@@ -898,8 +902,9 @@ PGO_PROF_GEN_FLAG
 LLVM_AR_FOUND
 LLVM_AR
 PROFILE_TASK
-DEF_MAKE_RULE
-DEF_MAKE_ALL_RULE
+MAKE_TARGET_BUILD_OPTIMIZED
+MAKE_TARGET_BUILD_PLAIN
+MAKE_TARGET_ALL
 ABIFLAGS
 LN
 MKDIR_P
@@ -1056,6 +1061,7 @@ with_assertions
 enable_optimizations
 with_lto
 enable_bolt
+with_bolt_libpython
 with_strict_overflow
 with_dsymutil
 with_address_sanitizer
@@ -1097,6 +1103,7 @@ PKG_CONFIG
 PKG_CONFIG_PATH
 PKG_CONFIG_LIBDIR
 MACHDEP
+_PYTHON_HOST_PLATFORM
 CC
 CFLAGS
 LDFLAGS
@@ -1105,6 +1112,8 @@ CPPFLAGS
 CPP
 HOSTRUNNER
 PROFILE_TASK
+BOLT_INSTRUMENT_FLAGS
+BOLT_APPLY_FLAGS
 LIBUUID_CFLAGS
 LIBUUID_LIBS
 LIBFFI_CFLAGS
@@ -1828,6 +1837,8 @@ Optional Packages:
   --with-lto=[full|thin|no|yes]
                           enable Link-Time-Optimization in any build (default
                           is no)
+  --with-bolt-libpython   enable BOLT optimization of libpython (WARNING:
+                          known to crash BOLT)
   --with-strict-overflow  if 'yes', add -fstrict-overflow to CFLAGS, else add
                           -fno-strict-overflow (default is no)
   --with-dsymutil         link debug information into final executable with
@@ -1905,6 +1916,14 @@ Some influential environment variables:
   PKG_CONFIG_LIBDIR
               path overriding pkg-config's built-in search path
   MACHDEP     name for machine-dependent library files
+  _PYTHON_HOST_PLATFORM
+              Forces a platform tag value for use in sysconfig data. This will
+              be calculated automatically in non-cross builds by running
+              sysconfig code in the bootstrapped interpreter. In cross builds,
+              an attempt will be made to derive an appropriate value in
+              configure. But some targets may derive incorrect values. This
+              variable can be set to force a value. Example values:
+              linux-x86_64, macosx-10.9-universal2, win-amd64
   CC          C compiler command
   CFLAGS      C compiler flags
   LDFLAGS     linker flags, e.g. -L<lib dir> if you have libraries in a
@@ -1916,6 +1935,10 @@ Some influential environment variables:
   HOSTRUNNER  Program to run CPython for the host platform
   PROFILE_TASK
               Python args for PGO generation task
+  BOLT_INSTRUMENT_FLAGS
+              Arguments to llvm-bolt when instrumenting binaries
+  BOLT_APPLY_FLAGS
+              Arguments to llvm-bolt when creating a BOLT optimized binary
   LIBUUID_CFLAGS
               C compiler flags for LIBUUID, overriding pkg-config
   LIBUUID_LIBS
@@ -3914,34 +3937,42 @@ fi
 $as_echo "\"$MACHDEP\"" >&6; }
 
 
-if test "$cross_compiling" = yes; then
-	case "$host" in
-	*-*-linux*)
-		case "$host_cpu" in
-		arm*)
-			_host_cpu=arm
-			;;
-		*)
-			_host_cpu=$host_cpu
-		esac
-		;;
-	*-*-cygwin*)
-		_host_cpu=
-		;;
-	*-*-vxworks*)
-		_host_cpu=$host_cpu
-		;;
-	wasm32-*-* | wasm64-*-*)
-		_host_cpu=$host_cpu
-		;;
-	*)
-		# for now, limit cross builds to known configurations
-		MACHDEP="unknown"
-		as_fn_error $? "cross build not supported for $host" "$LINENO" 5
-	esac
-	_PYTHON_HOST_PLATFORM="$MACHDEP${_host_cpu:+-$_host_cpu}"
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking _PYTHON_HOST_PLATFORM" >&5
+$as_echo_n "checking _PYTHON_HOST_PLATFORM... " >&6; }
+
+if test -z "${_PYTHON_HOST_PLATFORM}"; then
+    if test "$cross_compiling" = yes; then
+        case "$host" in
+        *-*-linux*)
+            case "$host_cpu" in
+            arm*)
+                _host_cpu=arm
+                ;;
+            *)
+                _host_cpu=$host_cpu
+            esac
+            ;;
+        *-*-cygwin*)
+            _host_cpu=
+            ;;
+        *-*-vxworks*)
+            _host_cpu=$host_cpu
+            ;;
+        wasm32-*-* | wasm64-*-*)
+            _host_cpu=$host_cpu
+            ;;
+        *)
+            # for now, limit cross builds to known configurations
+            MACHDEP="unknown"
+            as_fn_error $? "cross build not supported for $host" "$LINENO" 5
+        esac
+        _PYTHON_HOST_PLATFORM="$MACHDEP${_host_cpu:+-$_host_cpu}"
+    fi
 fi
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $_PYTHON_HOST_PLATFORM" >&5
+$as_echo "$_PYTHON_HOST_PLATFORM" >&6; }
+
 # Some systems cannot stand _XOPEN_SOURCE being defined at all; they
 # disable features if it is defined, without any means to access these
 # features as extensions. For these systems, we skip the definition of
@@ -7448,8 +7479,18 @@ $as_echo "no" >&6; }
 fi
 
 # Enable optimization flags
+# Which target `all` (the default make target) depends on.
+
+# Which target to evaluate for non-optimized builds.
+
 
 
+# Do a non-optimized generic build by default. Build configurations below
+# can override as appropriate.
+MAKE_TARGET_ALL="build-plain"
+MAKE_TARGET_BUILD_PLAIN="build_all"
+MAKE_TARGET_BUILD_OPTIMIZED="build-optimized-not-enabled"
+
 Py_OPT='false'
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for --enable-optimizations" >&5
 $as_echo_n "checking for --enable-optimizations... " >&6; }
@@ -7473,13 +7514,15 @@ fi
 
 
 if test "$Py_OPT" = 'true' ; then
+  # PGO is implied by optimizations mode.
+  PGO_ENABLED=1
+  MAKE_TARGET_ALL="build-optimized"
+  MAKE_TARGET_BUILD_OPTIMIZED="profile-pgo-apply-stamp"
+
   # Intentionally not forcing Py_LTO='true' here.  Too many toolchains do not
   # compile working code using it and both test_distutils and test_gdb are
   # broken when you do manage to get a toolchain that works with it.  People
   # who want LTO need to use --with-lto themselves.
-  DEF_MAKE_ALL_RULE="profile-opt"
-  REQUIRE_PGO="yes"
-  DEF_MAKE_RULE="build_all"
   case $CC in
     *gcc*)
       { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether C compiler accepts -fno-semantic-interposition" >&5
@@ -7523,13 +7566,7 @@ fi
       ;;
   esac
 elif test "$ac_sys_system" = "Emscripten" -o "$ac_sys_system" = "WASI"; then
-      DEF_MAKE_ALL_RULE="build_wasm"
-  REQUIRE_PGO="no"
-  DEF_MAKE_RULE="all"
-else
-  DEF_MAKE_ALL_RULE="build_all"
-  REQUIRE_PGO="no"
-  DEF_MAKE_RULE="all"
+      MAKE_TARGET_BUILD_PLAIN="build_wasm"
 fi
 
 
@@ -8039,7 +8076,8 @@ case $CC in
     if test $LLVM_PROF_FOUND = not-found
     then
       LLVM_PROF_ERR=yes
-      if test "${REQUIRE_PGO}" = "yes"
+
+      if test -n "${ENABLE_PGO}"
       then
         as_fn_error $? "llvm-profdata is required for a --enable-optimizations build but could not be found." "$LINENO" 5
       fi
@@ -8055,10 +8093,10 @@ case $CC in
         if test "${LLVM_PROF_FOUND}" = "not-found"
         then
           LLVM_PROF_ERR=yes
-          if test "${REQUIRE_PGO}" = "yes"
-	  then
-	    as_fn_error $? "llvm-profdata is required for a --enable-optimizations build but could not be found." "$LINENO" 5
-	  fi
+          if test -n "${ENABLE_PGO}"
+          then
+            as_fn_error $? "llvm-profdata is required for a --enable-optimizations build but could not be found." "$LINENO" 5
+          fi
         fi
         ;;
       *)
@@ -8101,10 +8139,19 @@ fi
 
 
 
+
+
 if test "$Py_BOLT" = 'true' ; then
-  PREBOLT_RULE="${DEF_MAKE_ALL_RULE}"
-  DEF_MAKE_ALL_RULE="bolt-opt"
-  DEF_MAKE_RULE="build_all"
+  MAKE_TARGET_BUILD_OPTIMIZED="profile-bolt-apply-stamp"
+
+  # Hook up make dependencies differently depending on whether PGO is
+  # enabled. See inline comment in Makefile.pre.in for how this works.
+  if test -n "${PGO_ENABLED}"
+  then
+    MAKE_BOLT_NATIVE_DEPENDENCY="profile-pgo-apply-stamp"
+  else
+    MAKE_BOLT_MAKE_DEPENDENCY="${MAKE_TARGET_BUILD_PLAIN}"
+  fi
 
 
   if test -n "$ac_tool_prefix"; then
@@ -8474,6 +8521,49 @@ $as_echo "\"Found merge-fdata\"" >&6; }
   fi
 fi
 
+# Enable BOLT optimizations of libpython. Optional for now due to known
+# crashes on LLVM 15. Seems to be fixed in LLVM 16.
+
+BOLT_BINARIES='$(BUILDPYTHON)'
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for --with-bolt-libpython" >&5
+$as_echo_n "checking for --with-bolt-libpython... " >&6; }
+
+# Check whether --with-bolt_libpython was given.
+if test "${with_bolt_libpython+set}" = set; then :
+  withval=$with_bolt_libpython; with_bolt_libpython="yes"
+else
+  with_bolt_libpython="no"
+fi
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_bolt_libpython" >&5
+$as_echo "$with_bolt_libpython" >&6; }
+
+if test "${enable_shared}" = "yes" -a "${with_bolt_libpython}" = "yes"
+then
+  BOLT_BINARIES="${BOLT_BINARIES} \$(INSTSONAME)"
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking BOLT_INSTRUMENT_FLAGS" >&5
+$as_echo_n "checking BOLT_INSTRUMENT_FLAGS... " >&6; }
+if test -z "${BOLT_INSTRUMENT_FLAGS}"
+then
+    BOLT_INSTRUMENT_FLAGS=
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $BOLT_INSTRUMENT_FLAGS" >&5
+$as_echo "$BOLT_INSTRUMENT_FLAGS" >&6; }
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking BOLT_APPLY_FLAGS" >&5
+$as_echo_n "checking BOLT_APPLY_FLAGS... " >&6; }
+if test -z "${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
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $BOLT_APPLY_FLAGS" >&5
+$as_echo "$BOLT_APPLY_FLAGS" >&6; }
+
 # XXX Shouldn't the code above that fiddles with BASECFLAGS and OPT be
 # merged with this chunk of code?
 
diff --git a/configure.ac b/configure.ac
index 115998e0753b26..e9f927c6de4ea4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -584,35 +584,47 @@ then
 fi
 AC_MSG_RESULT("$MACHDEP")
 
-AC_SUBST(_PYTHON_HOST_PLATFORM)
-if test "$cross_compiling" = yes; then
-	case "$host" in
-	*-*-linux*)
-		case "$host_cpu" in
-		arm*)
-			_host_cpu=arm
-			;;
-		*)
-			_host_cpu=$host_cpu
-		esac
-		;;
-	*-*-cygwin*)
-		_host_cpu=
-		;;
-	*-*-vxworks*)
-		_host_cpu=$host_cpu
-		;;
-	wasm32-*-* | wasm64-*-*)
-		_host_cpu=$host_cpu
-		;;
-	*)
-		# for now, limit cross builds to known configurations
-		MACHDEP="unknown"
-		AC_MSG_ERROR([cross build not supported for $host])
-	esac
-	_PYTHON_HOST_PLATFORM="$MACHDEP${_host_cpu:+-$_host_cpu}"
+AC_ARG_VAR(_PYTHON_HOST_PLATFORM, [
+  Forces a platform tag value for use in sysconfig data. This will be calculated
+  automatically in non-cross builds by running sysconfig code in the
+  bootstrapped interpreter. In cross builds, an attempt will be made to
+  derive an appropriate value in configure. But some targets may derive
+  incorrect values. This variable can be set to force a value. Example
+  values: linux-x86_64, macosx-10.9-universal2, win-amd64])
+AC_MSG_CHECKING(_PYTHON_HOST_PLATFORM)
+
+if test -z "${_PYTHON_HOST_PLATFORM}"; then
+    if test "$cross_compiling" = yes; then
+        case "$host" in
+        *-*-linux*)
+            case "$host_cpu" in
+            arm*)
+                _host_cpu=arm
+                ;;
+            *)
+                _host_cpu=$host_cpu
+            esac
+            ;;
+        *-*-cygwin*)
+            _host_cpu=
+            ;;
+        *-*-vxworks*)
+            _host_cpu=$host_cpu
+            ;;
+        wasm32-*-* | wasm64-*-*)
+            _host_cpu=$host_cpu
+            ;;
+        *)
+            # for now, limit cross builds to known configurations
+            MACHDEP="unknown"
+            AC_MSG_ERROR([cross build not supported for $host])
+        esac
+        _PYTHON_HOST_PLATFORM="$MACHDEP${_host_cpu:+-$_host_cpu}"
+    fi
 fi
 
+AC_MSG_RESULT([$_PYTHON_HOST_PLATFORM])
+
 # Some systems cannot stand _XOPEN_SOURCE being defined at all; they
 # disable features if it is defined, without any means to access these
 # features as extensions. For these systems, we skip the definition of
@@ -1722,8 +1734,18 @@ else
 fi
 
 # Enable optimization flags
-AC_SUBST(DEF_MAKE_ALL_RULE)
-AC_SUBST(DEF_MAKE_RULE)
+# Which target `all` (the default make target) depends on.
+AC_SUBST(MAKE_TARGET_ALL)
+# Which target to evaluate for non-optimized builds.
+AC_SUBST(MAKE_TARGET_BUILD_PLAIN)
+AC_SUBST(MAKE_TARGET_BUILD_OPTIMIZED)
+
+# Do a non-optimized generic build by default. Build configurations below
+# can override as appropriate.
+MAKE_TARGET_ALL="build-plain"
+MAKE_TARGET_BUILD_PLAIN="build_all"
+MAKE_TARGET_BUILD_OPTIMIZED="build-optimized-not-enabled"
+
 Py_OPT='false'
 AC_MSG_CHECKING(for --enable-optimizations)
 AC_ARG_ENABLE(optimizations, AS_HELP_STRING(
@@ -1741,13 +1763,15 @@ fi],
 [AC_MSG_RESULT(no)])
 
 if test "$Py_OPT" = 'true' ; then
+  # PGO is implied by optimizations mode.
+  PGO_ENABLED=1
+  MAKE_TARGET_ALL="build-optimized"
+  MAKE_TARGET_BUILD_OPTIMIZED="profile-pgo-apply-stamp"
+
   # Intentionally not forcing Py_LTO='true' here.  Too many toolchains do not
   # compile working code using it and both test_distutils and test_gdb are
   # broken when you do manage to get a toolchain that works with it.  People
   # who want LTO need to use --with-lto themselves.
-  DEF_MAKE_ALL_RULE="profile-opt"
-  REQUIRE_PGO="yes"
-  DEF_MAKE_RULE="build_all"
   case $CC in
     *gcc*)
       AX_CHECK_COMPILE_FLAG([-fno-semantic-interposition],[
@@ -1759,13 +1783,7 @@ if test "$Py_OPT" = 'true' ; then
 elif test "$ac_sys_system" = "Emscripten" -o "$ac_sys_system" = "WASI"; then
   dnl Emscripten does not support shared extensions yet. Build
   dnl "python.[js,wasm]", "pybuilddir.txt", and "platform" files.
-  DEF_MAKE_ALL_RULE="build_wasm"
-  REQUIRE_PGO="no"
-  DEF_MAKE_RULE="all"
-else
-  DEF_MAKE_ALL_RULE="build_all"
-  REQUIRE_PGO="no"
-  DEF_MAKE_RULE="all"
+  MAKE_TARGET_BUILD_PLAIN="build_wasm"
 fi
 
 AC_ARG_VAR(PROFILE_TASK, Python args for PGO generation task)
@@ -1967,7 +1985,8 @@ case $CC in
     if test $LLVM_PROF_FOUND = not-found
     then
       LLVM_PROF_ERR=yes
-      if test "${REQUIRE_PGO}" = "yes"
+
+      if test -n "${ENABLE_PGO}"
       then
         AC_MSG_ERROR([llvm-profdata is required for a --enable-optimizations build but could not be found.])
       fi
@@ -1983,10 +2002,10 @@ case $CC in
         if test "${LLVM_PROF_FOUND}" = "not-found"
         then
           LLVM_PROF_ERR=yes
-          if test "${REQUIRE_PGO}" = "yes"
-	  then
-	    AC_MSG_ERROR([llvm-profdata is required for a --enable-optimizations build but could not be found.])
-	  fi
+          if test -n "${ENABLE_PGO}"
+          then
+            AC_MSG_ERROR([llvm-profdata is required for a --enable-optimizations build but could not be found.])
+          fi
         fi
         ;;
       *)
@@ -2022,11 +2041,20 @@ else
 fi],
 [AC_MSG_RESULT(no)])
 
-AC_SUBST(PREBOLT_RULE)
+AC_SUBST(MAKE_BOLT_NATIVE_DEPENDENCY)
+AC_SUBST(MAKE_BOLT_MAKE_DEPENDENCY)
+
 if test "$Py_BOLT" = 'true' ; then
-  PREBOLT_RULE="${DEF_MAKE_ALL_RULE}"
-  DEF_MAKE_ALL_RULE="bolt-opt"
-  DEF_MAKE_RULE="build_all"
+  MAKE_TARGET_BUILD_OPTIMIZED="profile-bolt-apply-stamp"
+
+  # Hook up make dependencies differently depending on whether PGO is
+  # enabled. See inline comment in Makefile.pre.in for how this works.
+  if test -n "${PGO_ENABLED}"
+  then
+    MAKE_BOLT_NATIVE_DEPENDENCY="profile-pgo-apply-stamp"
+  else
+    MAKE_BOLT_MAKE_DEPENDENCY="${MAKE_TARGET_BUILD_PLAIN}"
+  fi
 
   AC_SUBST(READELF)
   AC_CHECK_TOOLS(READELF, [readelf], "notfound")
@@ -2067,6 +2095,39 @@ if test "$Py_BOLT" = 'true' ; then
   fi
 fi
 
+# Enable BOLT optimizations of libpython. Optional for now due to known
+# crashes on LLVM 15. Seems to be fixed in LLVM 16.
+AC_SUBST(BOLT_BINARIES)
+BOLT_BINARIES='$(BUILDPYTHON)'
+
+AC_MSG_CHECKING(for --with-bolt-libpython)
+AC_ARG_WITH(bolt_libpython,
+            AS_HELP_STRING([--with-bolt-libpython], [enable BOLT optimization of libpython (WARNING: known to crash BOLT)]),
+            [with_bolt_libpython="yes"],
+            [with_bolt_libpython="no"])
+AC_MSG_RESULT($with_bolt_libpython)
+
+if test "${enable_shared}" = "yes" -a "${with_bolt_libpython}" = "yes"
+then
+  BOLT_BINARIES="${BOLT_BINARIES} \$(INSTSONAME)"
+fi
+
+AC_ARG_VAR(BOLT_INSTRUMENT_FLAGS, Arguments to llvm-bolt when instrumenting binaries)
+AC_MSG_CHECKING(BOLT_INSTRUMENT_FLAGS)
+if test -z "${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?