Re: [PATCH] kbuild: Support clang-$ver builds
From: Peter Zijlstra <peterz@infradead.org>
Date: 2021-10-28 15:04:20
Also in:
lkml, llvm
Subsystem:
kernel build + files below scripts/ (unless maintained elsewhere), the rest · Maintainers:
Nathan Chancellor, Nicolas Schier, Linus Torvalds
On Thu, Oct 28, 2021 at 04:22:22PM +0200, Peter Zijlstra wrote:
On Thu, Oct 28, 2021 at 04:15:02PM +0200, Peter Zijlstra wrote:quoted
On Thu, Oct 28, 2021 at 11:07:40PM +0900, Masahiro Yamada wrote:quoted
On Thu, Oct 28, 2021 at 10:44 PM Peter Zijlstra [off-list ref] wrote:quoted
Hi, Debian (and derived) distros ship their compilers as -$ver suffixed binaries. For gcc it is sufficent to use: $ make CC=gcc-12 However, clang builds (esp. clang-lto) need a whole array of tools to be exactly right, leading to unweildy stuff like: $ make CC=clang-13 LD=ld.lld=14 AR=llvm-ar-13 NM=llvm-nm-13 OBJCOPY=llvm-objcopy-13 OBJDUMP=llvm-objdump-13 READELF=llvm-readelf-13 STRIP=llvm-strip-13 LLVM=1 which is, quite franktly, totally insane and unusable. Instead use the already mandatory LLVM variable to convey this, enabling one such as myself to use: $ make LLVM=-13 This also lets one quickly test different clang versions.Please read the commit log of a0d1c951ef08ed24f35129267e3595d86f57f5d3That's yuck, I like LLVM=-13 or LLVM=-12 much better to select between compilers. Means I don't have to remember wth they live and or wreck PATH.Even better, why not do something like: if test "${CC:0:5}" == "clang" then LLVM=1 LLVM_SFX=${CC:5} fi Then we can simply use: make CC=clang-12 and have it all just work.
Like so.. --- Makefile | 26 ++++++++++++++++---------- tools/scripts/Makefile.include | 22 ++++++++++++++-------- 2 files changed, 30 insertions(+), 18 deletions(-)
diff --git a/Makefile b/Makefile
index 30c7c81d0437..1d0d4494e01d 100644
--- a/Makefile
+++ b/Makefile@@ -423,9 +423,15 @@ HOST_LFS_CFLAGS := $(shell getconf LFS_CFLAGS 2>/dev/null) HOST_LFS_LDFLAGS := $(shell getconf LFS_LDFLAGS 2>/dev/null) HOST_LFS_LIBS := $(shell getconf LFS_LIBS 2>/dev/null) +CC_BASE = $(shell echo $(CC) | cut -b "1-5") +ifeq ($(shell test $(CC_BASE) = clang; echo $$?),0) +LLVM := 1 +LLVM_SFX := $(shell echo $(CC) | cut -b "6-") +endif + ifneq ($(LLVM),) -HOSTCC = clang -HOSTCXX = clang++ +HOSTCC = clang$(LLVM_SFX) +HOSTCXX = clang++$(LLVM_SFX) else HOSTCC = gcc HOSTCXX = g++
@@ -443,14 +449,14 @@ KBUILD_HOSTLDLIBS := $(HOST_LFS_LIBS) $(HOSTLDLIBS) # Make variables (CC, etc...) CPP = $(CC) -E ifneq ($(LLVM),) -CC = clang -LD = ld.lld -AR = llvm-ar -NM = llvm-nm -OBJCOPY = llvm-objcopy -OBJDUMP = llvm-objdump -READELF = llvm-readelf -STRIP = llvm-strip +CC = clang$(LLVM_SFX) +LD = ld.lld$(LLVM_SFX) +AR = llvm-ar$(LLVM_SFX) +NM = llvm-nm$(LLVM_SFX) +OBJCOPY = llvm-objcopy$(LLVM_SFX) +OBJDUMP = llvm-objdump$(LLVM_SFX) +READELF = llvm-readelf$(LLVM_SFX) +STRIP = llvm-strip$(LLVM_SFX) else CC = $(CROSS_COMPILE)gcc LD = $(CROSS_COMPILE)ld
diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
index 071312f5eb92..94c41083a7c7 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include@@ -51,12 +51,18 @@ define allow-override $(eval $(1) = $(2))) endef +CC_BASE = $(shell echo $(CC) | cut -b "1-5") +ifeq ($(shell test $(CC_BASE) = clang; echo $$?),0) +LLVM := 1 +LLVM_SFX := $(shell echo $(CC) | cut -b "6-") +endif + ifneq ($(LLVM),) -$(call allow-override,CC,clang) -$(call allow-override,AR,llvm-ar) -$(call allow-override,LD,ld.lld) -$(call allow-override,CXX,clang++) -$(call allow-override,STRIP,llvm-strip) +$(call allow-override,CC,clang$(LLVM_SFX)) +$(call allow-override,AR,llvm-ar$(LLVM_SFX)) +$(call allow-override,LD,ld.lld$(LLVM_SFX)) +$(call allow-override,CXX,clang++$(LLVM_SFX)) +$(call allow-override,STRIP,llvm-strip$(LLVM_SFX)) else # Allow setting various cross-compile vars or setting CROSS_COMPILE as a prefix. $(call allow-override,CC,$(CROSS_COMPILE)gcc)
@@ -69,9 +75,9 @@ endif CC_NO_CLANG := $(shell $(CC) -dM -E -x c /dev/null | grep -Fq "__clang__"; echo $$?) ifneq ($(LLVM),) -HOSTAR ?= llvm-ar -HOSTCC ?= clang -HOSTLD ?= ld.lld +HOSTAR ?= llvm-ar$(LLVM_SFX) +HOSTCC ?= clang$(LLVM_SFX) +HOSTLD ?= ld.lld$(LLVM_SFX) else HOSTAR ?= ar HOSTCC ?= gcc