Index: Mk/Uses/llvm.mk
===================================================================
--- /dev/null
+++ Mk/Uses/llvm.mk
@@ -0,0 +1,94 @@
+# Provides support to depend on LLVM
+#
+# It chooses the llvm port to be used based on the following constraint:
+#	1) no constraints given						=> ${LLVM_DEFAULT}
+#	2) exact constraint given					=> ${exact}
+#	2) max constraint given && ${max} < ${LLVM_DEFAULT}		=> ${max}
+#	3) min constraint given && ${LLVM_DEFAULT} < ${LLVM_DEFAULT}	=> ${LLVM_DEFAULT}
+
+# Usage:
+# 	USES=	llvm			- default version chosen
+# 	USES=	llvm:15			- exact constraint
+# 	USES=	llvm:min=9		- min constraint: max(min,default)
+# 	USES=	llvm:max=10		- max constraint: min(max,default)
+# 	USES=	llvm:min=10,max=11	- all constraint: max(min(max,default),default)
+
+.if ! defined(_INCLUDE_USES_LLVM_MK)
+_INCLUDE_USES_LLVM_MK=	YES
+
+_LLVM_MK_VALID_VERSIONS=	7 8 9 10 11 12 13 14 15
+_LLVM_MK_VALID_CONSTRAINTS=	min max
+_LLVM_MK_VALID_MODES=		build run
+
+# === parse mode arguments ===
+_LLVM_MK_MODES=	# empty
+.  for _mode in ${_LLVM_MK_VALID_MODES}
+.    if ${llvm_ARGS:M${_mode}}
+_LLVM_MK_MODES+=	${_mode}
+.    endif
+.  endfor
+.  if empty(_LLVM_MK_MODES)
+_LLVM_MK_MODES=	build
+.  endif
+
+# === parse version arguments ===
+_LLVM_MK_VERSION=	# empty
+.  for _ver in ${_LLVM_MK_VALID_VERSIONS}
+.    if ${llvm_ARGS:M${_ver}}
+.      if !empty(_LLVM_MK_VERSION)
+BROKEN=		USES=llvm:${llvm_ARGS} contains multiple version definitions
+.      else
+_LLVM_MK_VERSION=	${_ver}
+.      endif
+.    endif
+.  endfor
+.  if empty(_LLVM_MK_VERSION)
+_LLVM_MK_VERSION=	${LLVM_DEFAULT}
+.  endif
+
+# === handle constraints ===
+.  for _constraint in ${_LLVM_MK_VALID_CONSTRAINTS}
+_version=	${llvm_ARGS:M${_constraint}=[0-9]*:S/${_constraint}=//}
+.    if !empty(_version)
+_LLVM_MK_CONSTRAINT_${_constraint}=	${_version}
+.    endif
+.  endfor
+
+.  if !empty(_LLVM_MK_CONSTRAINT_min)
+.    if ${_LLVM_MK_CONSTRAINT_min} > ${_LLVM_MK_VERSION}
+_LLVM_MK_VERSION=	${_LLVM_MK_CONSTRAINT_min}
+.    endif
+.  endif
+
+.  if !empty(_LLVM_MK_CONSTRAINT_max)
+.    if ${_LLVM_MK_CONSTRAINT_max} < ${_LLVM_MK_VERSION}
+_LLVM_MK_VERSION=	${_LLVM_MK_CONSTRAINT_max}
+.    endif
+.  endif
+
+# === define helpers for the dependencies ===
+.  for _ver in ${_LLVM_MK_VALID_VERSIONS:N1[0-9]}
+_LLVM_MK_SUFFIX_${_ver}=	${_ver}0
+.  endfor
+
+.  for _ver in ${_LLVM_MK_VALID_VERSIONS}
+_LLVM_MK_SUFFIX_${_ver}?=	${_ver}
+.  endfor
+
+# === define variables to depend on and export ===
+_LLVM_MK_PORT=		devel/llvm${_LLVM_MK_SUFFIX_${_LLVM_MK_VERSION}}
+_LLVM_MK_PATH=		llvm-config${_LLVM_MK_SUFFIX_${_LLVM_MK_VERSION}}
+_LLVM_MK_PREFIX=	${PREFIX}/llvm${_LLVM_MK_SUFFIX_${_LLVM_MK_VERSION}}
+
+# == add actual dependencies ===
+.  for _mode in ${_LLVM_MK_MODES}
+${_mode:tu}_DEPENDS+=	${_LLVM_MK_PATH}:${_LLVM_MK_PORT}
+.  endfor
+
+# == export config ===
+LLVM_PORT=		${_LLVM_MK_PORT}
+LLVM_CONFIG=		${_LLVM_MK_PATH}
+LLVM_VERSION=		${_LLVM_MK_VERSION}
+LLVM_PREFIX=		${_LLVM_MK_PREFIX}
+
+.endif
Index: devel/android-tools-simpleperf/Makefile
===================================================================
--- devel/android-tools-simpleperf/Makefile
+++ devel/android-tools-simpleperf/Makefile
@@ -10,19 +10,17 @@
 
 LICENSE=	APACHE20
 
-BUILD_DEPENDS=	llvm-config${LLVM_DEFAULT}:devel/llvm${LLVM_DEFAULT}
-
 USE_GITHUB=	yes
 GH_TUPLE=	jbeich:platform_system_extras:${DISTVERSIONFULL} \
 		aosp-mirror:platform_system_core:${DISTVERSIONFULL}:core \
 		aosp-mirror:platform_bionic:${DISTVERSIONFULL}:bionic/bionic
 
-USES=		compiler:c++11-lib ncurses uidfix
+USES=		compiler:c++11-lib ncurses uidfix llvm:9
 BUILD_WRKSRC=	${WRKSRC}/simpleperf
 INSTALL_WRKSRC=	${BUILD_WRKSRC}
 TEST_WRKSRC=	${BUILD_WRKSRC}
 MAKEFILE=	${FILESDIR}/Makefile
-MAKE_ENV=	BINDIR="${PREFIX}/bin" LLVM_CONFIG="llvm-config${LLVM_DEFAULT}"
+MAKE_ENV=	BINDIR="${PREFIX}/bin" LLVM_CONFIG=${LLVM_CONFIG}
 ALL_TARGET=	all
 TEST_TARGET=	test
 LDFLAGS+=	-Wl,--as-needed # avoid overlinking (llvm deps)