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Date: Thu, 28 Oct 2021 15:43:48 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: nathan@...nel.org, ndesaulniers@...gle.com, masahiroy@...nel.org,
michal.lkml@...kovi.net
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
linux-kbuild@...r.kernel.org, llvm@...ts.linux.dev
Subject: [PATCH] kbuild: Support clang-$ver builds
Hi,
Debian (and derived) distros ship their compilers as -$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.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
Makefile | 27 +++++++++++++++++----------
tools/scripts/Makefile.include | 23 +++++++++++++++--------
2 files changed, 32 insertions(+), 18 deletions(-)
diff --git a/Makefile b/Makefile
index 30c7c81d0437..a38f38f7f190 100644
--- a/Makefile
+++ b/Makefile
@@ -423,9 +423,16 @@ HOST_LFS_CFLAGS := $(shell getconf LFS_CFLAGS 2>/dev/null)
HOST_LFS_LDFLAGS := $(shell getconf LFS_LDFLAGS 2>/dev/null)
HOST_LFS_LIBS := $(shell getconf LFS_LIBS 2>/dev/null)
+# When LLVM=-ver use clang-ver binaries, useful for Debian and other
+# multi-version setups
+ifeq ($(shell test $(LLVM) -lt 0; echo $$?),0)
+LLVM_SFX=$(LLVM)
+export LLVM_SFX
+endif
+
ifneq ($(LLVM),)
-HOSTCC = clang
-HOSTCXX = clang++
+HOSTCC = clang$(LLVM_SFX)
+HOSTCXX = clang++$(LLVM_SFX)
else
HOSTCC = gcc
HOSTCXX = g++
@@ -443,14 +450,14 @@ KBUILD_HOSTLDLIBS := $(HOST_LFS_LIBS) $(HOSTLDLIBS)
# Make variables (CC, etc...)
CPP = $(CC) -E
ifneq ($(LLVM),)
-CC = clang
-LD = ld.lld
-AR = llvm-ar
-NM = llvm-nm
-OBJCOPY = llvm-objcopy
-OBJDUMP = llvm-objdump
-READELF = llvm-readelf
-STRIP = llvm-strip
+CC = clang$(LLVM_SFX)
+LD = ld.lld$(LLVM_SFX)
+AR = llvm-ar$(LLVM_SFX)
+NM = llvm-nm$(LLVM_SFX)
+OBJCOPY = llvm-objcopy$(LLVM_SFX)
+OBJDUMP = llvm-objdump$(LLVM_SFX)
+READELF = llvm-readelf$(LLVM_SFX)
+STRIP = llvm-strip$(LLVM_SFX)
else
CC = $(CROSS_COMPILE)gcc
LD = $(CROSS_COMPILE)ld
diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
index 071312f5eb92..a2b53cc91378 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -51,12 +51,19 @@ define allow-override
$(eval $(1) = $(2)))
endef
+# When LLVM=-ver use clang-ver binaries, useful for Debian and other
+# multi-version setups
+ifeq ($(shell test $(LLVM) -lt 0; echo $$?),0)
+LLVM_SFX=$(LLVM)
+export LLVM_SFX
+endif
+
ifneq ($(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 +76,9 @@ 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
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