--- a/Makefile.in
+++ b/Makefile.in
@@ -213,14 +213,19 @@ ifneq (,$(wildcard $(DIST)/bin/applicati
 BUILDID = $(shell $(PYTHON) $(srcdir)/config/printconfigsetting.py $(DIST)/bin/application.ini App BuildID)
 else
 BUILDID = $(shell $(PYTHON) $(srcdir)/config/printconfigsetting.py $(DIST)/bin/platform.ini Build BuildID)
 endif
 
 #XXX: this is a hack, since we don't want to clobber for MSVC
 # PGO support, but we can't do this test in client.mk
 ifneq ($(OS_ARCH)_$(GNU_CC), WINNT_)
+# No point in clobbering if PGO has been explicitly disabled.
+ifndef NO_PROFILE_GUIDED_OPTIMIZE
 maybe_clobber_profiledbuild: clobber_all
 else
 maybe_clobber_profiledbuild:
 endif
+else
+maybe_clobber_profiledbuild:
+endif
 
 .PHONY: maybe_clobber_profiledbuild

--- a/client.mk
+++ b/client.mk
@@ -926,16 +926,40 @@ real_l10n-checkout:
 	if test "$$conflicts" ; then \
 	  echo "$(MAKE): *** Conflicts during checkout." ;\
 	  echo "$$conflicts" ;\
 	  echo "$(MAKE): Refer to $(CVSCO_LOGFILE_L10N) for full log." ;\
 	  false; \
 	else true; \
 	fi
 
+####################################
+# Profile-Guided Optimization
+#  To use this, you should set the following variables in your mozconfig
+#    mk_add_options PROFILE_GEN_SCRIPT=/path/to/profile-script
+#
+#  The profile script should exercise the functionality to be included
+#  in the profile feedback.
+#
+#  This is up here, outside of the MOZ_CURRENT_PROJECT logic so that this
+#  is usable in multi-pass builds, where you might not have a runnable
+#  application until all the build passes and postflight scripts have run.
+ifdef MOZ_OBJDIR
+  PGO_OBJDIR = $(MOZ_OBJDIR)
+else
+  PGO_OBJDIR := $(TOPSRCDIR)
+endif
+
+profiledbuild::
+	$(MAKE) -f $(TOPSRCDIR)/client.mk build MOZ_PROFILE_GENERATE=1
+	OBJDIR=${PGO_OBJDIR} $(PROFILE_GEN_SCRIPT)
+	$(MAKE) -f $(TOPSRCDIR)/client.mk maybe_clobber_profiledbuild
+	$(MAKE) -f $(TOPSRCDIR)/client.mk build MOZ_PROFILE_USE=1
+
+
 #####################################################
 # First Checkout
 
 ifdef _IS_FIRST_CHECKOUT
 # First time, do build target in a new process to pick up new files.
 build::
 	$(MAKE) -f $(TOPSRCDIR)/client.mk build
 else
@@ -953,17 +977,17 @@ MOZ_BUILD_DATE = $(shell $(PYTHON) $(TOP
 export MOZ_BUILD_DATE
 endif
 endif
 endif
 
 #####################################################
 # Preflight, before building any project
 
-build profiledbuild alldep preflight_all::
+build alldep preflight_all::
 ifeq (,$(MOZ_CURRENT_PROJECT)$(if $(MOZ_PREFLIGHT_ALL),,1))
 # Don't run preflight_all for individual projects in multi-project builds
 # (when MOZ_CURRENT_PROJECT is set.)
 ifndef MOZ_BUILD_PROJECTS
 # Building a single project, OBJDIR is usable.
 	set -e; \
 	for mkfile in $(MOZ_PREFLIGHT_ALL); do \
 	  $(MAKE) -f $(TOPSRCDIR)/$$mkfile preflight_all TOPSRCDIR=$(TOPSRCDIR) OBJDIR=$(OBJDIR) MOZ_OBJDIR=$(MOZ_OBJDIR); \
@@ -977,17 +1001,17 @@ else
 	done
 endif
 endif
 
 # If we're building multiple projects, but haven't specified which project,
 # loop through them.
 
 ifeq (,$(MOZ_CURRENT_PROJECT)$(if $(MOZ_BUILD_PROJECTS),,1))
-configure depend build profiledbuild install export libs clean realclean distclean alldep preflight postflight::
+configure depend build install export libs clean realclean distclean alldep preflight postflight maybe_clobber_profiledbuild::
 	set -e; \
 	for app in $(MOZ_BUILD_PROJECTS); do \
 	  $(MAKE) -f $(TOPSRCDIR)/client.mk $@ MOZ_CURRENT_PROJECT=$$app; \
 	done
 
 else
 
 # MOZ_CURRENT_PROJECT: either doing a single-project build, or building an
@@ -1067,68 +1091,54 @@ endif
 # Depend
 
 depend:: $(OBJDIR)/Makefile $(OBJDIR)/config.status
 	$(MOZ_MAKE) export && $(MOZ_MAKE) depend
 
 ####################################
 # Preflight
 
-build profiledbuild alldep preflight::
+build alldep preflight::
 ifdef MOZ_PREFLIGHT
 	set -e; \
 	for mkfile in $(MOZ_PREFLIGHT); do \
 	  $(MAKE) -f $(TOPSRCDIR)/$$mkfile preflight TOPSRCDIR=$(TOPSRCDIR) OBJDIR=$(OBJDIR) MOZ_OBJDIR=$(MOZ_OBJDIR); \
 	done
 endif
 
 ####################################
 # Build it
 
 build::  $(OBJDIR)/Makefile $(OBJDIR)/config.status
 	$(MOZ_MAKE)
 
 ####################################
-# Profile-feedback build (gcc only)
-#  To use this, you should set the following variables in your mozconfig
-#    mk_add_options PROFILE_GEN_SCRIPT=/path/to/profile-script
-#
-#  The profile script should exercise the functionality to be included
-#  in the profile feedback.
-
-profiledbuild:: $(OBJDIR)/Makefile $(OBJDIR)/config.status
-	$(MOZ_MAKE) MOZ_PROFILE_GENERATE=1
-	OBJDIR=${OBJDIR} $(PROFILE_GEN_SCRIPT)
-	$(MOZ_MAKE) maybe_clobber_profiledbuild
-	$(MOZ_MAKE) MOZ_PROFILE_USE=1
-
-####################################
 # Other targets
 
 # Pass these target onto the real build system
-install export libs clean realclean distclean alldep:: $(OBJDIR)/Makefile $(OBJDIR)/config.status
+install export libs clean realclean distclean alldep maybe_clobber_profiledbuild:: $(OBJDIR)/Makefile $(OBJDIR)/config.status
 	$(MOZ_MAKE) $@
 
 ####################################
 # Postflight
 
-build profiledbuild alldep postflight::
+build alldep postflight::
 ifdef MOZ_POSTFLIGHT
 	set -e; \
 	for mkfile in $(MOZ_POSTFLIGHT); do \
 	  $(MAKE) -f $(TOPSRCDIR)/$$mkfile postflight TOPSRCDIR=$(TOPSRCDIR) OBJDIR=$(OBJDIR) MOZ_OBJDIR=$(MOZ_OBJDIR); \
 	done
 endif
 
 endif # MOZ_CURRENT_PROJECT
 
 ####################################
 # Postflight, after building all projects
 
-build profiledbuild alldep postflight_all::
+build alldep postflight_all::
 ifeq (,$(MOZ_CURRENT_PROJECT)$(if $(MOZ_POSTFLIGHT_ALL),,1))
 # Don't run postflight_all for individual projects in multi-project builds
 # (when MOZ_CURRENT_PROJECT is set.)
 ifndef MOZ_BUILD_PROJECTS
 # Building a single project, OBJDIR is usable.
 	set -e; \
 	for mkfile in $(MOZ_POSTFLIGHT_ALL); do \
 	  $(MAKE) -f $(TOPSRCDIR)/$$mkfile postflight_all TOPSRCDIR=$(TOPSRCDIR) OBJDIR=$(OBJDIR) MOZ_OBJDIR=$(MOZ_OBJDIR); \
@@ -1156,9 +1166,9 @@ cleansrcdir:
 	fi;
 
 # (! IS_FIRST_CHECKOUT)
 endif
 
 echo-variable-%:
 	@echo $($*)
 
-.PHONY: checkout real_checkout depend build profiledbuild export libs alldep install clean realclean distclean cleansrcdir pull_all build_all clobber clobber_all pull_and_build_all everything configure preflight_all preflight postflight postflight_all
+.PHONY: checkout real_checkout depend build profiledbuild maybe_clobber_profiledbuild export libs alldep install clean realclean distclean cleansrcdir pull_all build_all clobber clobber_all pull_and_build_all everything configure preflight_all preflight postflight postflight_all

--- a/config/autoconf.mk.in
+++ b/config/autoconf.mk.in
@@ -278,16 +278,17 @@ ACDEFINES	= @MOZ_DEFINES@
 WARNINGS_AS_ERRORS = @WARNINGS_AS_ERRORS@
 
 MOZ_OPTIMIZE	= @MOZ_OPTIMIZE@
 MOZ_OPTIMIZE_FLAGS = @MOZ_OPTIMIZE_FLAGS@
 MOZ_OPTIMIZE_LDFLAGS = @MOZ_OPTIMIZE_LDFLAGS@
 
 MOZ_RTTI_FLAGS_ON = @_MOZ_RTTI_FLAGS_ON@
 
+MOZ_PROFILE_GUIDED_OPTIMIZE_DISABLE = @MOZ_PROFILE_GUIDED_OPTIMIZE_DISABLE@
 PROFILE_GEN_CFLAGS = @PROFILE_GEN_CFLAGS@
 PROFILE_GEN_LDFLAGS = @PROFILE_GEN_LDFLAGS@
 PROFILE_USE_CFLAGS = @PROFILE_USE_CFLAGS@
 PROFILE_USE_LDFLAGS = @PROFILE_USE_LDFLAGS@
 
 XCFLAGS		= @XCFLAGS@
 XLDFLAGS	= @XLDFLAGS@
 XLIBS		= @XLIBS@

--- a/config/config.mk
+++ b/config/config.mk
@@ -346,16 +346,21 @@ ifndef _ENABLE_PIC
 DSO_CFLAGS=
 ifeq ($(OS_ARCH)_$(HAVE_GCC3_ABI),Darwin_1)
 DSO_PIC_CFLAGS=-mdynamic-no-pic
 else
 DSO_PIC_CFLAGS=
 endif
 endif
 
+# This comes from configure
+ifdef MOZ_PROFILE_GUIDED_OPTIMIZE_DISABLE
+NO_PROFILE_GUIDED_OPTIMIZE = 1
+endif
+
 # Enable profile-based feedback
 ifndef NO_PROFILE_GUIDED_OPTIMIZE
 ifdef MOZ_PROFILE_GENERATE
 # No sense in profiling tools
 ifndef INTERNAL_TOOLS
 OS_CFLAGS += $(PROFILE_GEN_CFLAGS)
 OS_CXXFLAGS += $(PROFILE_GEN_CFLAGS)
 OS_LDFLAGS += $(PROFILE_GEN_LDFLAGS)

--- a/configure.in
+++ b/configure.in
@@ -6545,16 +6545,25 @@ fi
 
 dnl ========================================================
 dnl Profile guided optimization
 dnl ========================================================
 dnl Test for profiling options
 dnl Under gcc 3.3, use -fprofile-arcs/-fbranch-probabilities
 dnl Under gcc 3.4+, use -fprofile-generate/-fprofile-use
 
+dnl Provide a switch to disable PGO even when called via profiledbuild.
+MOZ_ARG_DISABLE_BOOL(profile-guided-optimization,
+[  --disable-profile-guided-optimization
+                           Don't build with PGO even if called via make profiledbuild],
+MOZ_PROFILE_GUIDED_OPTIMIZE_DISABLE=1,
+MOZ_PROFILE_GUIDED_OPTIMIZE_DISABLE=)
+
+AC_SUBST(MOZ_PROFILE_GUIDED_OPTIMIZE_DISABLE)
+
 _SAVE_CFLAGS="$CFLAGS"
 CFLAGS="$CFLAGS -fprofile-generate"
 
 AC_MSG_CHECKING([whether C compiler supports -fprofile-generate])
 AC_TRY_COMPILE([], [return 0;],
                [ PROFILE_GEN_CFLAGS="-fprofile-generate"
                  result="yes" ], result="no")
 AC_MSG_RESULT([$result])