diff --git a/sys/conf/Makefile.amd64 b/sys/conf/Makefile.amd64
index d34359f1d30b..696ef55a3fb0 100644
--- a/sys/conf/Makefile.amd64
+++ b/sys/conf/Makefile.amd64
@@ -37,6 +37,9 @@ INCLUDES+= -I$S/contrib/libfdt
 CFLAGS+=	-fno-omit-frame-pointer -mno-omit-leaf-frame-pointer
 .endif
 
+ASM_CFLAGS.acpi_wakecode.S=	${CLANG_NO_IAS34}
+ASM_CFLAGS.mpboot.S=		${CLANG_NO_IAS34}
+
 %BEFORE_DEPEND
 
 %OBJS
diff --git a/sys/conf/Makefile.i386 b/sys/conf/Makefile.i386
index 621ebff79e19..6b1eca42f1bb 100644
--- a/sys/conf/Makefile.i386
+++ b/sys/conf/Makefile.i386
@@ -32,6 +32,9 @@ S=	../../..
 
 INCLUDES+= -I$S/contrib/libfdt
 
+ASM_CFLAGS.acpi_wakecode.S=	${CLANG_NO_IAS34}
+ASM_CFLAGS.mpboot.s=		${CLANG_NO_IAS34}
+
 %BEFORE_DEPEND
 
 %OBJS
diff --git a/sys/conf/Makefile.pc98 b/sys/conf/Makefile.pc98
index 28d0956912bc..9d0f25b57a57 100644
--- a/sys/conf/Makefile.pc98
+++ b/sys/conf/Makefile.pc98
@@ -30,6 +30,8 @@ S=	../../..
 .endif
 .include "$S/conf/kern.pre.mk"
 
+ASM_CFLAGS.mpboot.s=		${CLANG_NO_IAS34}
+
 %BEFORE_DEPEND
 
 %OBJS
diff --git a/sys/conf/kern.mk b/sys/conf/kern.mk
index 3cf3d94e1d04..157f5b50a1b0 100644
--- a/sys/conf/kern.mk
+++ b/sys/conf/kern.mk
@@ -29,9 +29,16 @@ NO_WSOMETIMES_UNINITIALIZED=	-Wno-error-sometimes-uninitialized
 CWARNEXTRA?=	-Wno-error-tautological-compare -Wno-error-empty-body \
 		-Wno-error-parentheses-equality -Wno-error-unused-function \
 		-Wno-error-pointer-sign -Wno-error-format -Wno-error-parentheses
+
+CLANG_NO_IAS= -no-integrated-as
+.if ${COMPILER_VERSION} < 30500
+# XXX: clang < 3.5 integrated-as doesn't grok .codeNN directives
+CLANG_NO_IAS34= -no-integrated-as
+.endif
 .endif
 
 .if ${COMPILER_TYPE} == "gcc"
+GCC_MS_EXTENSIONS= -fms-extensions
 .if ${COMPILER_VERSION} >= 40300
 # Catch-all for all the things that are in our tree, but for which we're
 # not yet ready for this compiler. Note: we likely only really "support"
@@ -168,9 +175,8 @@ CFLAGS+=	-fstack-protector
 CFLAGS+=	-gdwarf-2
 .endif
 
-CFLAGS+= ${CWARNEXTRA}
-
-CFLAGS+= ${CFLAGS.${COMPILER_TYPE}}
+CFLAGS+= ${CWARNEXTRA} ${CWARNFLAGS} ${CWARNFLAGS.${.IMPSRC:T}}
+CFLAGS+= ${CFLAGS.${COMPILER_TYPE}} ${CFLAGS.${.IMPSRC}}
 
 # Tell bmake not to mistake standard targets for things to be searched for
 # or expect to ever be up-to-date.
@@ -199,6 +205,3 @@ CFLAGS+=        -std=iso9899:1999
 .else # CSTD
 CFLAGS+=        -std=${CSTD}
 .endif # CSTD
-
-# Pull in any CWARNFLAGS the modules have added.
-CFLAGS+= ${CWARNFLAGS} ${CWARNFLAGS.${.IMPSRC:T}}
diff --git a/sys/conf/kern.pre.mk b/sys/conf/kern.pre.mk
index 21a42900f993..48982c5de5b6 100644
--- a/sys/conf/kern.pre.mk
+++ b/sys/conf/kern.pre.mk
@@ -103,13 +103,7 @@ CFLAGS.gcc+=${CFLAGS_ARCH_PARAMS}
 WERROR?= -Werror
 
 # XXX LOCORE means "don't declare C stuff" not "for locore.s".
-ASM_CFLAGS= -x assembler-with-cpp -DLOCORE ${CFLAGS}
-
-.if ${COMPILER_TYPE} == "clang"
-CLANG_NO_IAS= -no-integrated-as
-.else
-GCC_MS_EXTENSIONS= -fms-extensions
-.endif
+ASM_CFLAGS= -x assembler-with-cpp -DLOCORE ${CFLAGS} ${ASM_CFLAGS.${.IMPSRC}} 
 
 .if defined(PROFLEVEL) && ${PROFLEVEL} >= 1
 CFLAGS+=	-DGPROF
diff --git a/sys/modules/bios/smapi/Makefile b/sys/modules/bios/smapi/Makefile
index 30c9058dea2f..f55ab5af3bbf 100644
--- a/sys/modules/bios/smapi/Makefile
+++ b/sys/modules/bios/smapi/Makefile
@@ -8,3 +8,5 @@ SRCS=	smapi.c smapi_bios.S \
 	bus_if.h device_if.h
 
 .include <bsd.kmod.mk>
+
+CFLAGS.smapi_bios.S=	${CLANG_NO_IAS34}