Merge tag 'llvmlinux-for-v3.15' of git://git.linuxfoundation.org/llvmlinux/kernel

Pull llvm patches from Behan Webster:
"These are some initial updates to support compiling the kernel with
clang.

These patches have been through the proper reviews to the best of my
ability, and have been soaking in linux-next for a few weeks. These
patches by themselves still do not completely allow clang to be used
with the kernel code, but lay the foundation for other patches which
are still under review.

Several other of the LLVMLinux patches have been already added via
maintainer trees"

* tag 'llvmlinux-for-v3.15' of git://git.linuxfoundation.org/llvmlinux/kernel:
x86: LLVMLinux: Fix "incomplete type const struct x86cpu_device_id"
x86 kbuild: LLVMLinux: More cc-options added for clang
x86, acpi: LLVMLinux: Remove nested functions from Thinkpad ACPI
LLVMLinux: Add support for clang to compiler.h and new compiler-clang.h
LLVMLinux: Remove warning about returning an uninitialized variable
kbuild: LLVMLinux: Fix LINUX_COMPILER definition script for compilation with clang
Documentation: LLVMLinux: Update Documentation/dontdiff
kbuild: LLVMLinux: Adapt warnings for compilation with clang
kbuild: LLVMLinux: Add Kbuild support for building kernel with Clang

Documentation/dontdiff

···
 *.a
 *.aux
+*.bc
 *.bin
 *.bz2
 *.cis
···
 *.i
 *.jpeg
 *.ko
+*.ll
 *.log
 *.lst
 *.lzma
···
 *.out
 *.patch
 *.pdf
+*.plist
 *.png
 *.pot
 *.ps

Makefile

···
 HOSTCFLAGS   = -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer
 HOSTCXXFLAGS = -O2
 
+ifeq ($(shell $(HOSTCC) -v 2>&1 | grep -c "clang version"), 1)
+HOSTCFLAGS  += -Wno-unused-value -Wno-unused-parameter \
+		-Wno-missing-field-initializers -fno-delete-null-pointer-checks
+endif
+
 # Decide whether to build built-in, modular, or both.
 # Normally, just do built-in.
 
···
 
 export quiet Q KBUILD_VERBOSE
 
+ifneq ($(CC),)
+ifeq ($(shell $(CC) -v 2>&1 | grep -c "clang version"), 1)
+COMPILER := clang
+else
+COMPILER := gcc
+endif
+export COMPILER
+endif
 
 # Look for make include files relative to root of kernel src
 MAKEFLAGS += --include-dir=$(srctree)
···
 		   -fno-strict-aliasing -fno-common \
 		   -Werror-implicit-function-declaration \
 		   -Wno-format-security \
-		   -fno-delete-null-pointer-checks
+		   $(call cc-option,-fno-delete-null-pointer-checks,)
 KBUILD_AFLAGS_KERNEL :=
 KBUILD_CFLAGS_KERNEL :=
 KBUILD_AFLAGS   := -D__ASSEMBLY__
···
 endif
 KBUILD_CFLAGS += $(stackp-flag)
 
+ifeq ($(COMPILER),clang)
+KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,)
+KBUILD_CPPFLAGS += $(call cc-option,-Wno-unknown-warning-option,)
+KBUILD_CFLAGS += $(call cc-disable-warning, unused-variable)
+KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier)
+KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
+# Quiet clang warning: comparison of unsigned expression < 0 is always false
+KBUILD_CFLAGS += $(call cc-disable-warning, tautological-compare)
+# CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the
+# source of a reference will be _MergedGlobals and not on of the whitelisted names.
+# See modpost pattern 2
+KBUILD_CFLAGS += $(call cc-option, -mno-global-merge,)
+else
+
 # This warning generated too much noise in a regular build.
 # Use make W=1 to enable this warning (see scripts/Makefile.build)
 KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
+endif
 
 ifdef CONFIG_FRAME_POINTER
 KBUILD_CFLAGS	+= -fno-omit-frame-pointer -fno-optimize-sibling-calls

arch/x86/Makefile

···
 
         # this works around some issues with generating unwind tables in older gccs
         # newer gccs do it by default
-        KBUILD_CFLAGS += -maccumulate-outgoing-args
+        KBUILD_CFLAGS += $(call cc-option,-maccumulate-outgoing-args)
 endif
 
 # Make sure compiler does not have buggy stack-protector support.

include/asm-generic/cmpxchg-local.h

···
 #include <linux/types.h>
 #include <linux/irqflags.h>
 
-extern unsigned long wrong_size_cmpxchg(volatile void *ptr);
+extern unsigned long wrong_size_cmpxchg(volatile void *ptr)
+	__noreturn;
 
 /*
  * Generic version of __cmpxchg_local (disables interrupts). Takes an unsigned

include/linux/compiler-clang.h

···
+#ifndef __LINUX_COMPILER_H
+#error "Please don't include <linux/compiler-clang.h> directly, include <linux/compiler.h> instead."
+#endif
+
+/* Some compiler specific definitions are overwritten here
+ * for Clang compiler
+ */
+
+#ifdef uninitialized_var
+#undef uninitialized_var
+#define uninitialized_var(x) x = *(&(x))
+#endif

include/linux/compiler.h

···
 # include <linux/compiler-intel.h>
 #endif
 
+/* Clang compiler defines __GNUC__. So we will overwrite implementations
+ * coming from above header files here
+ */
+#ifdef __clang__
+#include <linux/compiler-clang.h>
+#endif
+
 /*
  * Generic compiler-dependent macros required for kernel
  * build go below this comment. Actual compiler/compiler version

include/linux/mod_devicetable.h

···
  * See documentation of "x86_match_cpu" for details.
  */
 
+/*
+ * MODULE_DEVICE_TABLE expects this struct to be called x86cpu_device_id.
+ * Although gcc seems to ignore this error, clang fails without this define.
+ */
+#define x86cpu_device_id x86_cpu_id
 struct x86_cpu_id {
 	__u16 vendor;
 	__u16 family;

scripts/Makefile.build

···
 warning-1 := -Wextra -Wunused -Wno-unused-parameter
 warning-1 += -Wmissing-declarations
 warning-1 += -Wmissing-format-attribute
-warning-1 += -Wmissing-prototypes
+warning-1 += $(call cc-option, -Wmissing-prototypes)
 warning-1 += -Wold-style-definition
 warning-1 += $(call cc-option, -Wmissing-include-dirs)
 warning-1 += $(call cc-option, -Wunused-but-set-variable)
 warning-1 += $(call cc-disable-warning, missing-field-initializers)
+
+# Clang
+warning-1 += $(call cc-disable-warning, initializer-overrides)
+warning-1 += $(call cc-disable-warning, unused-value)
+warning-1 += $(call cc-disable-warning, format)
+warning-1 += $(call cc-disable-warning, unknown-warning-option)
+warning-1 += $(call cc-disable-warning, sign-compare)
+warning-1 += $(call cc-disable-warning, format-zero-length)
+warning-1 += $(call cc-disable-warning, uninitialized)
+warning-1 += $(call cc-option, -fcatch-undefined-behavior)
 
 warning-2 := -Waggregate-return
 warning-2 += -Wcast-align

scripts/mkcompile_h

···
   echo \#define LINUX_COMPILE_BY \"`echo $LINUX_COMPILE_BY | $UTS_TRUNCATE`\"
   echo \#define LINUX_COMPILE_HOST \"`echo $LINUX_COMPILE_HOST | $UTS_TRUNCATE`\"
 
-  echo \#define LINUX_COMPILER \"`$CC -v 2>&1 | tail -n 1`\"
+  echo \#define LINUX_COMPILER \"`$CC -v 2>&1 | grep ' version '`\"
 ) > .tmpcompile
 
 # Only replace the real compile.h if the new one is different,