From 3abe71105f2640de7c9f3fcac880b3ed4e40a906 Mon Sep 17 00:00:00 2001 From: Peter Jung Date: Sat, 13 Dec 2025 11:33:01 +0100 Subject: [PATCH 03/11] autofdo Signed-off-by: Peter Jung --- Makefile | 9 +++++---- arch/Kconfig | 11 +++++++++++ scripts/Makefile.autofdo | 12 +++++++++--- scripts/Makefile.lib | 9 ++++++--- scripts/Makefile.propeller | 20 ++++++++++++++++---- scripts/Makefile.vmlinux_o | 3 ++- 6 files changed, 49 insertions(+), 15 deletions(-) diff --git a/Makefile b/Makefile index 23cc6c39819b..de1d81ee0b86 100644 --- a/Makefile +++ b/Makefile @@ -1230,14 +1230,15 @@ PHONY += vmlinux # not for decompressors. LDFLAGS_vmlinux in arch/*/boot/compressed/Makefile is # unrelated; the decompressors just happen to have the same base name, # arch/*/boot/compressed/vmlinux. -# Export LDFLAGS_vmlinux only to scripts/Makefile.vmlinux. +# Export LDFLAGS_vmlinux only to scripts/Makefile.vmlinux, and +# scripts/Makefile.vmlinux_o. # # _LDFLAGS_vmlinux is a workaround for the 'private export' bug: # https://savannah.gnu.org/bugs/?61463 # For Make > 4.4, the following simple code will work: -# vmlinux: private export LDFLAGS_vmlinux := $(LDFLAGS_vmlinux) -vmlinux: private _LDFLAGS_vmlinux := $(LDFLAGS_vmlinux) -vmlinux: export LDFLAGS_vmlinux = $(_LDFLAGS_vmlinux) +# vmlinux vmlinux_o: private export LDFLAGS_vmlinux := $(LDFLAGS_vmlinux) +vmlinux vmlinux_o: private _LDFLAGS_vmlinux := $(LDFLAGS_vmlinux) +vmlinux vmlinux_o: export LDFLAGS_vmlinux = $(_LDFLAGS_vmlinux) vmlinux: vmlinux.o $(KBUILD_LDS) modpost $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.vmlinux diff --git a/arch/Kconfig b/arch/Kconfig index 61130b88964b..6f0995ce7dd2 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -886,6 +886,17 @@ config AUTOFDO_CLANG If unsure, say N. +config AUTOFDO_PROFILE_ACCURATE + bool "Assert AutoFDO profile is accurate (EXPERIMENTAL)" + depends on AUTOFDO_CLANG + help + This option asserts that the AutoFDO profile (specified + in CLANG_AUTOFDO_PROFILE) is collected from a representative + workload, allowing the Clang compiler to perform more + aggressive optimizations. + + If unsure, say N. + config ARCH_SUPPORTS_PROPELLER_CLANG bool diff --git a/scripts/Makefile.autofdo b/scripts/Makefile.autofdo index 1caf2457e585..36abeae2accd 100644 --- a/scripts/Makefile.autofdo +++ b/scripts/Makefile.autofdo @@ -11,14 +11,20 @@ endif ifdef CLANG_AUTOFDO_PROFILE CFLAGS_AUTOFDO_CLANG += -fprofile-sample-use=$(CLANG_AUTOFDO_PROFILE) -ffunction-sections CFLAGS_AUTOFDO_CLANG += -fsplit-machine-functions +ifdef CONFIG_AUTOFDO_PROFILE_ACCURATE + CFLAGS_AUTOFDO_CLANG += -fprofile-sample-accurate +endif endif ifdef CONFIG_LTO_CLANG_THIN + _ldflags_autofdo := --mllvm=-enable-fs-discriminator=true --mllvm=-improved-fs-discriminator=true -plugin-opt=thinlto + _ldflags_autofdo += -plugin-opt=-split-machine-functions ifdef CLANG_AUTOFDO_PROFILE - KBUILD_LDFLAGS += --lto-sample-profile=$(CLANG_AUTOFDO_PROFILE) + _ldflags_autofdo += --lto-sample-profile=$(CLANG_AUTOFDO_PROFILE) endif - KBUILD_LDFLAGS += --mllvm=-enable-fs-discriminator=true --mllvm=-improved-fs-discriminator=true -plugin-opt=thinlto - KBUILD_LDFLAGS += -plugin-opt=-split-machine-functions + # TODO: change LDFLAGS_vmlinux to KBUILD_LDFLAGS when kernel modules + # are supported. + LDFLAGS_vmlinux += $(_ldflags_autofdo) endif export CFLAGS_AUTOFDO_CLANG diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 1d581ba5df66..0f6874e8d584 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -108,20 +108,23 @@ endif # # Enable AutoFDO build flags except some files or directories we don't want to # enable (depends on variables AUTOFDO_PROFILE_obj.o and AUTOFDO_PROFILE). -# +# TODO: change '$(part-of-builtin)' to '$(is-kernel-object)' when the AutoFDO +# build supports modules. ifeq ($(CONFIG_AUTOFDO_CLANG),y) _c_flags += $(if $(patsubst n%,, \ - $(AUTOFDO_PROFILE_$(target-stem).o)$(AUTOFDO_PROFILE)$(is-kernel-object)), \ + $(AUTOFDO_PROFILE_$(target-stem).o)$(AUTOFDO_PROFILE)$(part-of-builtin)), \ $(CFLAGS_AUTOFDO_CLANG)) endif # # Enable Propeller build flags except some files or directories we don't want to # enable (depends on variables AUTOFDO_PROPELLER_obj.o and PROPELLER_PROFILE). +# TODO: change '$(part-of-builtin)' to '$(is-kernel-object)' when the Propeller +# build supports modules. # ifdef CONFIG_PROPELLER_CLANG _c_flags += $(if $(patsubst n%,, \ - $(AUTOFDO_PROFILE_$(target-stem).o)$(AUTOFDO_PROFILE)$(PROPELLER_PROFILE))$(is-kernel-object), \ + $(PROPELLER_PROFILE_$(target-stem).o)$(PROPELLER_PROFILE)$(part-of-builtin)), \ $(CFLAGS_PROPELLER_CLANG)) endif diff --git a/scripts/Makefile.propeller b/scripts/Makefile.propeller index 48a660128e25..8c3e514dbcc0 100644 --- a/scripts/Makefile.propeller +++ b/scripts/Makefile.propeller @@ -3,7 +3,7 @@ # Enable available and selected Clang Propeller features. ifdef CLANG_PROPELLER_PROFILE_PREFIX CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=list=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt -ffunction-sections - KBUILD_LDFLAGS += --symbol-ordering-file=$(CLANG_PROPELLER_PROFILE_PREFIX)_ld_profile.txt --no-warn-symbol-ordering + _ldflags_propeller := --symbol-ordering-file=$(CLANG_PROPELLER_PROFILE_PREFIX)_ld_profile.txt --no-warn-symbol-ordering else # Starting with Clang v20, the '-fbasic-block-sections=labels' option is # deprecated. Use the recommended '-fbasic-block-address-map' option. @@ -13,8 +13,14 @@ else else CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=labels endif + # Disable Machine Function Splitter for Propeller. + # Propeller profile generation requires Machine Function Splitter to be disabled. + # We use -fno-split-machine-functions to override any prior AutoFDO/PGO flags + #(in Makefile.lib), assuming Propeller options are applied afterward. + CFLAGS_PROPELLER_CLANG += -fno-split-machine-functions endif + # Propeller requires debug information to embed module names in the profiles. # If CONFIG_DEBUG_INFO is not enabled, set -gmlt option. Skip this for AutoFDO, # as the option should already be set. @@ -26,14 +32,20 @@ endif ifdef CONFIG_LTO_CLANG_THIN ifdef CLANG_PROPELLER_PROFILE_PREFIX - KBUILD_LDFLAGS += --lto-basic-block-sections=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt + _ldflags_propeller += --lto-basic-block-sections=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt else ifeq ($(call test-ge, $(CONFIG_LLD_VERSION), 200000),y) - KBUILD_LDFLAGS += --lto-basic-block-address-map + _ldflags_propeller += --lto-basic-block-address-map else - KBUILD_LDFLAGS += --lto-basic-block-sections=labels + _ldflags_propeller += --lto-basic-block-sections=labels endif + # Again, we need to disable Machine Function Splitter. + LDFLAGS_vmlinux := $(filter-out -plugin-opt=-split-machine-functions, $(LDFLAGS_vmlinux)) endif endif +# TODO: change LDFLAGS_vmlinux to KBUILD_LDFLAGS when kernel modules +# are supported. +LDFLAGS_vmlinux += $(_ldflags_propeller) + export CFLAGS_PROPELLER_CLANG diff --git a/scripts/Makefile.vmlinux_o b/scripts/Makefile.vmlinux_o index 23c8751285d7..ee070bf35385 100644 --- a/scripts/Makefile.vmlinux_o +++ b/scripts/Makefile.vmlinux_o @@ -56,7 +56,8 @@ vmlinux-o-ld-args-$(CONFIG_BUILTIN_MODULE_RANGES) += -Map=$@.map quiet_cmd_ld_vmlinux.o = LD $@ cmd_ld_vmlinux.o = \ - $(LD) ${KBUILD_LDFLAGS} -r -o $@ \ + $(LD) $(KBUILD_LDFLAGS) \ + $(filter-out -pie, $(LDFLAGS_vmlinux)) -r -o $@ \ $(vmlinux-o-ld-args-y) \ $(addprefix -T , $(initcalls-lds)) \ --whole-archive vmlinux.a --no-whole-archive \ -- 2.52.0