diff --git a/README.md b/README.md
index 4376e79d924..0aef21f25c3 100644
--- a/README.md
+++ b/README.md
@@ -31,7 +31,7 @@ The installed toolchains have to match the one Qt was compiled with.
 
 You can build Qt Creator with
 
-    # Optional, needed for the Clang Code Model:
+    # Optional, needed for the Clang Code Model if llvm-config is not in PATH:
     export LLVM_INSTALL_DIR=/path/to/llvm (or "set" on Windows)
     # Optional, needed to let the QbsProjectManager plugin use system Qbs:
     export QBS_INSTALL_DIR=/path/to/qbs
@@ -129,7 +129,7 @@ For detailed information on the supported compilers, see
        * Install LLVM/Clang - see the section "Get LLVM/Clang for the Clang
          Code Model".
        * Set the environment variable LLVM_INSTALL_DIR to the LLVM/Clang
-         installation directory.
+         installation directory if llvm-config is not in PATH.
        * When you launch Qt Creator, activate the Clang Code Model plugin as
          described in doc/src/editors/creator-clang-codemodel.qdoc.
 
diff --git a/src/plugins/clangcodemodel/clangcodemodel.pro b/src/plugins/clangcodemodel/clangcodemodel.pro
index 55a3bf45720..bd10d49e207 100644
--- a/src/plugins/clangcodemodel/clangcodemodel.pro
+++ b/src/plugins/clangcodemodel/clangcodemodel.pro
@@ -3,6 +3,8 @@ include(../../shared/clang/clang_installation.pri)
 
 include(../../shared/clang/clang_defines.pri)
 
+requires(!isEmpty(LLVM_VERSION))
+
 SOURCES += \
     clangactivationsequencecontextprocessor.cpp \
     clangactivationsequenceprocessor.cpp \
diff --git a/src/plugins/plugins.pro b/src/plugins/plugins.pro
index d1c774128bb..b01145d3a61 100644
--- a/src/plugins/plugins.pro
+++ b/src/plugins/plugins.pro
@@ -96,21 +96,15 @@ exists(../shared/qbs/qbs.pro)|!isEmpty(QBS_INSTALL_DIR): \
     SUBDIRS += \
         qbsprojectmanager
 
-# prefer qmake variable set on command line over env var
-isEmpty(LLVM_INSTALL_DIR):LLVM_INSTALL_DIR=$$(LLVM_INSTALL_DIR)
-exists($$LLVM_INSTALL_DIR) {
-    SUBDIRS += clangcodemodel
+SUBDIRS += \
+    clangcodemodel
 
-    QTC_NO_CLANG_LIBTOOLING=$$(QTC_NO_CLANG_LIBTOOLING)
-    isEmpty(QTC_NO_CLANG_LIBTOOLING) {
-        SUBDIRS += clangrefactoring
-        SUBDIRS += clangpchmanager
-    } else {
-        warning("Building the Clang refactoring and the pch manager plugins are disabled.")
-    }
+QTC_NO_CLANG_LIBTOOLING=$$(QTC_NO_CLANG_LIBTOOLING)
+isEmpty(QTC_NO_CLANG_LIBTOOLING) {
+    SUBDIRS += clangrefactoring
+    SUBDIRS += clangpchmanager
 } else {
-    warning("Set LLVM_INSTALL_DIR to build the Clang Code Model. " \
-            "For details, see doc/src/editors/creator-clang-codemodel.qdoc.")
+    warning("Building the Clang refactoring and the pch manager plugins are disabled.")
 }
 
 isEmpty(IDE_PACKAGE_MODE) {
diff --git a/src/shared/clang/clang_installation.pri b/src/shared/clang/clang_installation.pri
index 572d0441b25..63ad0ad538c 100644
--- a/src/shared/clang/clang_installation.pri
+++ b/src/shared/clang/clang_installation.pri
@@ -1,7 +1,18 @@
 isEmpty(LLVM_INSTALL_DIR):LLVM_INSTALL_DIR=$$(LLVM_INSTALL_DIR)
 LLVM_INSTALL_DIR = $$clean_path($$LLVM_INSTALL_DIR)
-isEmpty(LLVM_INSTALL_DIR): error("No LLVM_INSTALL_DIR provided")
-!exists($$LLVM_INSTALL_DIR): error("LLVM_INSTALL_DIR does not exist: $$LLVM_INSTALL_DIR")
+
+!isEmpty(LLVM_INSTALL_DIR):!exists($$LLVM_INSTALL_DIR) {
+    error("Explicitly given LLVM_INSTALL_DIR does not exist: $$LLVM_INSTALL_DIR")
+}
+
+defineReplace(llvmWarningOrError) {
+    warningText = $$1
+    errorText = $$2
+    isEmpty(errorText): errorText = $$warningText
+    isEmpty(LLVM_INSTALL_DIR): warning($$warningText)
+    else: error($$errorText)
+    return(false)
+}
 
 # Expected input: "3.9.1", "5.0.0svn", "5.0.1git-81029f14223"
 defineReplace(extractVersion)      { return($$replace(1, ^(\\d+\\.\\d+\\.\\d+).*$, \\1)) }
@@ -69,20 +80,6 @@ defineReplace(findClangLibInLibDir) {
     }
 }
 
-defineReplace(findClangOnWindows) {
-    FILE_EXTS = a dll
-    msvc: FILE_EXTS = lib dll
-    for (suffix, $$list(lib bin)) {
-        for (libname, $$list(clang libclang)) {
-            for (ext, FILE_EXTS) {
-                exists("$${LLVM_INSTALL_DIR}/$${suffix}/$${libname}.$${ext}") {
-                    return($${LLVM_INSTALL_DIR}/$${suffix}/)
-                }
-            }
-        }
-    }
-}
-
 CLANGTOOLING_LIBS=-lclangTooling -lclangIndex -lclangFrontend -lclangParse -lclangSerialization \
                   -lclangSema -lclangEdit -lclangAnalysis -lclangDriver -lclangDynamicASTMatchers \
                   -lclangASTMatchers -lclangToolingCore -lclangAST -lclangLex -lclangBasic
@@ -91,65 +88,87 @@ win32:CLANGTOOLING_LIBS += -lversion
 BIN_EXTENSION =
 win32: BIN_EXTENSION = .exe
 
-llvm_config = $$system_quote($$LLVM_INSTALL_DIR/bin/llvm-config)
-requires(exists($$llvm_config$$BIN_EXTENSION))
-#message("llvm-config found, querying it for paths and version")
-LLVM_LIBDIR = $$quote($$system($$llvm_config --libdir, lines))
-LLVM_INCLUDEPATH = $$system($$llvm_config --includedir, lines)
+isEmpty(LLVM_INSTALL_DIR) {
+    llvm_config = llvm-config
+} else {
+    llvm_config = $$system_quote($$LLVM_INSTALL_DIR/bin/llvm-config)
+    requires(exists($$llvm_config$$BIN_EXTENSION))
+}
+
 output = $$system($$llvm_config --version, lines)
 LLVM_VERSION = $$extractVersion($$output)
-msvc {
-    LLVM_STATIC_LIBS_STRING += $$system($$llvm_config --libnames, lines)
+isEmpty(LLVM_VERSION) {
+    $$llvmWarningOrError(\
+        "Cannot determine clang version. Set LLVM_INSTALL_DIR to build the Clang Code Model",\
+        "LLVM_INSTALL_DIR does not contain a valid llvm-config, candidate: $$llvm_config")
+} else:!versionIsAtLeast($$LLVM_VERSION, 5, 0, 0): {
+    # CLANG-UPGRADE-CHECK: Adapt minimum version numbers.
+    $$llvmWarningOrError(\
+        "LLVM/Clang version >= 5.0.0 required, version provided: $$LLVM_VERSION")
+    LLVM_VERSION =
 } else {
-    LLVM_STATIC_LIBS_STRING += $$system($$llvm_config --libs, lines)
-}
-LLVM_STATIC_LIBS_STRING += $$system($$llvm_config --system-libs, lines)
-
-LLVM_STATIC_LIBS = $$split(LLVM_STATIC_LIBS_STRING, " ")
-
-LIBCLANG_MAIN_HEADER = $$LLVM_INCLUDEPATH/clang-c/Index.h
-!exists($$LIBCLANG_MAIN_HEADER): error("Cannot find libclang's main header file, candidate: $$LIBCLANG_MAIN_HEADER")
-!exists($$LLVM_LIBDIR): error("Cannot detect lib dir for clang, candidate: $$LLVM_LIBDIR")
-CLANG_LIB = $$findClangLibInLibDir($$LLVM_LIBDIR)
-isEmpty(CLANG_LIB): error("Cannot find Clang shared library in $$LLVM_LIBDIR")
-
-!contains(QMAKE_DEFAULT_LIBDIRS, $$LLVM_LIBDIR): LIBCLANG_LIBS = -L$${LLVM_LIBDIR}
-LIBCLANG_LIBS += $${CLANG_LIB}
-
-QTC_NO_CLANG_LIBTOOLING=$$(QTC_NO_CLANG_LIBTOOLING)
-isEmpty(QTC_NO_CLANG_LIBTOOLING) {
-    QTC_FORCE_CLANG_LIBTOOLING = $$(QTC_FORCE_CLANG_LIBTOOLING)
-    versionIsEqual($$LLVM_VERSION, 5, 0)|!isEmpty(QTC_FORCE_CLANG_LIBTOOLING) {
-        !contains(QMAKE_DEFAULT_LIBDIRS, $$LLVM_LIBDIR): LIBTOOLING_LIBS = -L$${LLVM_LIBDIR}
-        LIBTOOLING_LIBS += $$CLANGTOOLING_LIBS $$LLVM_STATIC_LIBS
-        contains(QMAKE_DEFAULT_INCDIRS, $$LLVM_INCLUDEPATH): LLVM_INCLUDEPATH =
+    LLVM_LIBDIR = $$quote($$system($$llvm_config --libdir, lines))
+    LLVM_BINDIR = $$quote($$system($$llvm_config --bindir, lines))
+    LLVM_INCLUDEPATH = $$system($$llvm_config --includedir, lines)
+    msvc {
+        LLVM_STATIC_LIBS_STRING += $$system($$llvm_config --libnames, lines)
     } else {
-        warning("Clang LibTooling is disabled because only version 5.0 is supported.")
+        LLVM_STATIC_LIBS_STRING += $$system($$llvm_config --libs, lines)
     }
-} else {
-    warning("Clang LibTooling is disabled.")
+    LLVM_STATIC_LIBS_STRING += $$system($$llvm_config --system-libs, lines)
+
+    LLVM_STATIC_LIBS = $$split(LLVM_STATIC_LIBS_STRING, " ")
+
+    LIBCLANG_MAIN_HEADER = $$LLVM_INCLUDEPATH/clang-c/Index.h
+    !exists($$LIBCLANG_MAIN_HEADER) {
+        $$llvmWarningOrError(\
+            "Cannot find libclang's main header file, candidate: $$LIBCLANG_MAIN_HEADER")
+    }
+    !exists($$LLVM_LIBDIR) {
+        $$llvmWarningOrError("Cannot detect lib dir for clang, candidate: $$LLVM_LIBDIR")
+    }
+    !exists($$LLVM_BINDIR) {
+        $$llvmWarningOrError("Cannot detect bin dir for clang, candidate: $$LLVM_BINDIR")
+    }
+    CLANG_LIB = $$findClangLibInLibDir($$LLVM_LIBDIR)
+    isEmpty(CLANG_LIB) {
+        $$llvmWarningOrError("Cannot find Clang shared library in $$LLVM_LIBDIR")
+    }
+
+    !contains(QMAKE_DEFAULT_LIBDIRS, $$LLVM_LIBDIR): LIBCLANG_LIBS = -L$${LLVM_LIBDIR}
+    LIBCLANG_LIBS += $${CLANG_LIB}
+
+    QTC_NO_CLANG_LIBTOOLING=$$(QTC_NO_CLANG_LIBTOOLING)
+    isEmpty(QTC_NO_CLANG_LIBTOOLING) {
+        QTC_FORCE_CLANG_LIBTOOLING = $$(QTC_FORCE_CLANG_LIBTOOLING)
+        versionIsEqual($$LLVM_VERSION, 5, 0)|!isEmpty(QTC_FORCE_CLANG_LIBTOOLING) {
+            !contains(QMAKE_DEFAULT_LIBDIRS, $$LLVM_LIBDIR): LIBTOOLING_LIBS = -L$${LLVM_LIBDIR}
+            LIBTOOLING_LIBS += $$CLANGTOOLING_LIBS $$LLVM_STATIC_LIBS
+            contains(QMAKE_DEFAULT_INCDIRS, $$LLVM_INCLUDEPATH): LLVM_INCLUDEPATH =
+        } else {
+            warning("Clang LibTooling is disabled because only version 5.0 is supported.")
+        }
+    } else {
+        warning("Clang LibTooling is disabled.")
+    }
+
+    # Remove unwanted flags. It is a workaround for linking.
+    # It is not intended for cross compiler linking.
+    LLVM_CXXFLAGS = $$system($$llvm_config --cxxflags, lines)
+    LLVM_CXXFLAGS ~= s,-fno-exceptions,
+    LLVM_CXXFLAGS ~= s,-std=c++11,
+    LLVM_CXXFLAGS ~= s,-std=c++0x,
+    LLVM_CXXFLAGS ~= s,-O\S*,
+    LLVM_CXXFLAGS ~= s,/O\S*,
+    LLVM_CXXFLAGS ~= s,/W4,
+    LLVM_CXXFLAGS ~= s,/EH\S*,
+    LLVM_CXXFLAGS ~= s,-Werror=date-time,
+    LLVM_CXXFLAGS ~= s,-Wcovered-switch-default,
+    LLVM_CXXFLAGS ~= s,-fPIC,
+    LLVM_CXXFLAGS ~= s,-pedantic,
+    LLVM_CXXFLAGS ~= s,-Wstring-conversion,
+    # split-dwarf needs objcopy which does not work via icecc out-of-the-box
+    LLVM_CXXFLAGS ~= s,-gsplit-dwarf,
+
+    LLVM_IS_COMPILED_WITH_RTTI = $$system($$llvm_config --has-rtti, lines)
 }
-
-isEmpty(LLVM_VERSION): error("Cannot determine clang version at $$LLVM_INSTALL_DIR")
-!versionIsAtLeast($$LLVM_VERSION, 5, 0, 0): { # CLANG-UPGRADE-CHECK: Adapt minimum version numbers.
-    error("LLVM/Clang version >= 5.0.0 required, version provided: $$LLVM_VERSION")
-}
-
-# Remove unwanted flags. It is a workaround for linking. It is not intended for cross compiler linking.
-LLVM_CXXFLAGS = $$system($$llvm_config --cxxflags, lines)
-LLVM_CXXFLAGS ~= s,-fno-exceptions,
-LLVM_CXXFLAGS ~= s,-std=c++11,
-LLVM_CXXFLAGS ~= s,-std=c++0x,
-LLVM_CXXFLAGS ~= s,-O\S*,
-LLVM_CXXFLAGS ~= s,/O\S*,
-LLVM_CXXFLAGS ~= s,/W4,
-LLVM_CXXFLAGS ~= s,/EH\S*,
-LLVM_CXXFLAGS ~= s,-Werror=date-time,
-LLVM_CXXFLAGS ~= s,-Wcovered-switch-default,
-LLVM_CXXFLAGS ~= s,-fPIC,
-LLVM_CXXFLAGS ~= s,-pedantic,
-LLVM_CXXFLAGS ~= s,-Wstring-conversion,
-# split-dwarf needs objcopy which does not work via icecc out-of-the-box
-LLVM_CXXFLAGS ~= s,-gsplit-dwarf,
-
-LLVM_IS_COMPILED_WITH_RTTI = $$system($$llvm_config --has-rtti, lines)
diff --git a/src/tools/clangbackend/clangbackend.pro b/src/tools/clangbackend/clangbackend.pro
index 32ca5f08422..3b7c5de518c 100644
--- a/src/tools/clangbackend/clangbackend.pro
+++ b/src/tools/clangbackend/clangbackend.pro
@@ -6,6 +6,8 @@ include(../../qtcreatortool.pri)
 include(../../shared/clang/clang_installation.pri)
 include(source/clangbackendclangipc-source.pri)
 
+requires(!isEmpty(LLVM_VERSION))
+
 QT += core network
 QT -= gui
 
diff --git a/src/tools/clangpchmanagerbackend/clangpchmanagerbackend.pro b/src/tools/clangpchmanagerbackend/clangpchmanagerbackend.pro
index 8dab349dd34..b54db0be04a 100644
--- a/src/tools/clangpchmanagerbackend/clangpchmanagerbackend.pro
+++ b/src/tools/clangpchmanagerbackend/clangpchmanagerbackend.pro
@@ -33,4 +33,4 @@ unix {
     !disable_external_rpath: QMAKE_LFLAGS += -Wl,-rpath,$$shell_quote($${LLVM_LIBDIR})
 }
 
-DEFINES += CLANG_COMPILER_PATH=\"R\\\"xxx($$LLVM_INSTALL_DIR/bin/clang)xxx\\\"\"
+DEFINES += CLANG_COMPILER_PATH=\"R\\\"xxx($${LLVM_BINDIR}/clang)xxx\\\"\"
diff --git a/src/tools/tools.pro b/src/tools/tools.pro
index 23268020b79..9cd8728ef32 100644
--- a/src/tools/tools.pro
+++ b/src/tools/tools.pro
@@ -20,17 +20,14 @@ mac {
     SUBDIRS += iostool
 }
 
-isEmpty(LLVM_INSTALL_DIR):LLVM_INSTALL_DIR=$$(LLVM_INSTALL_DIR)
-exists($$LLVM_INSTALL_DIR) {
-    SUBDIRS += clangbackend
+SUBDIRS += clangbackend
 
-    QTC_NO_CLANG_LIBTOOLING=$$(QTC_NO_CLANG_LIBTOOLING)
-    isEmpty(QTC_NO_CLANG_LIBTOOLING) {
-        SUBDIRS += clangrefactoringbackend
-        SUBDIRS += clangpchmanagerbackend
-    } else {
-        warning("Building the Clang refactoring back end and the pch manager plugins are disabled.")
-    }
+QTC_NO_CLANG_LIBTOOLING=$$(QTC_NO_CLANG_LIBTOOLING)
+isEmpty(QTC_NO_CLANG_LIBTOOLING) {
+    SUBDIRS += clangrefactoringbackend
+    SUBDIRS += clangpchmanagerbackend
+} else {
+    warning("Building the Clang refactoring back end and the pch manager plugins are disabled.")
 }
 
 isEmpty(BUILD_CPLUSPLUS_TOOLS):BUILD_CPLUSPLUS_TOOLS=$$(BUILD_CPLUSPLUS_TOOLS)
diff --git a/tests/tests.pro b/tests/tests.pro
index a7c5bc6bd23..08d0e9438d0 100644
--- a/tests/tests.pro
+++ b/tests/tests.pro
@@ -1,4 +1,2 @@
 TEMPLATE=subdirs
-SUBDIRS += auto manual tools
-isEmpty(LLVM_INSTALL_DIR):LLVM_INSTALL_DIR=$$(LLVM_INSTALL_DIR)
-exists($$LLVM_INSTALL_DIR):SUBDIRS += unit
+SUBDIRS += auto manual tools unit
diff --git a/tests/unit/unittest/clang_dependency.pri b/tests/unit/unittest/clang_dependency.pri
index bbce04a527a..9c2a3c57a3c 100644
--- a/tests/unit/unittest/clang_dependency.pri
+++ b/tests/unit/unittest/clang_dependency.pri
@@ -1,27 +1,26 @@
-isEmpty(LLVM_INSTALL_DIR):LLVM_INSTALL_DIR=$$(LLVM_INSTALL_DIR)
-!isEmpty(LLVM_INSTALL_DIR) {
 include(../../../src/shared/clang/clang_installation.pri)
-requires(!isEmpty(LIBCLANG_LIBS))
-equals(LLVM_IS_COMPILED_WITH_RTTI, "NO") : message("LLVM needs to be compiled with RTTI!")
-requires(equals(LLVM_IS_COMPILED_WITH_RTTI, "YES"))
+!isEmpty(LLVM_VERSION) {
+    requires(!isEmpty(LIBCLANG_LIBS))
+    equals(LLVM_IS_COMPILED_WITH_RTTI, "NO") : message("LLVM needs to be compiled with RTTI!")
+    requires(equals(LLVM_IS_COMPILED_WITH_RTTI, "YES"))
 
-DEFINES += CLANG_UNIT_TESTS
-INCLUDEPATH += $$LLVM_INCLUDEPATH
-win32 {
-    LIBS += -lVersion
+    DEFINES += CLANG_UNIT_TESTS
+    INCLUDEPATH += $$LLVM_INCLUDEPATH
+    win32 {
+        LIBS += -lVersion
 
-    # set run path for clang.dll dependency
-    bin_path = $$LLVM_INSTALL_DIR/bin
-    bin_path ~= s,/,\\,g
-    # the below gets added to later by testcase.prf
-    check.commands = cd . & set PATH=$$bin_path;%PATH%& cmd /c
+        # set run path for clang.dll dependency
+        bin_path = $$LLVM_BINDIR
+        bin_path ~= s,/,\\,g
+        # the below gets added to later by testcase.prf
+        check.commands = cd . & set PATH=$$bin_path;%PATH%& cmd /c
+    }
+
+    LIBS += $$LIBTOOLING_LIBS $$LIBCLANG_LIBS
+    QMAKE_RPATHDIR += $$LLVM_LIBDIR
+
+    LLVM_CXXFLAGS ~= s,-g\d?,
+    QMAKE_CXXFLAGS += $$LLVM_CXXFLAGS
+
+    DEFINES += CLANG_COMPILER_PATH=\"R\\\"xxx($$LLVM_BINDIR/clang)xxx\\\"\"
 }
-
-LIBS += $$LIBTOOLING_LIBS $$LIBCLANG_LIBS
-QMAKE_RPATHDIR += $$LLVM_LIBDIR
-
-LLVM_CXXFLAGS ~= s,-g\d?,
-QMAKE_CXXFLAGS += $$LLVM_CXXFLAGS
-}
-
-DEFINES += CLANG_COMPILER_PATH=\"R\\\"xxx($$LLVM_INSTALL_DIR/bin/clang)xxx\\\"\"
diff --git a/tests/unit/unittest/creator_dependency.pri b/tests/unit/unittest/creator_dependency.pri
index f86f9e9967e..ae82403f00e 100644
--- a/tests/unit/unittest/creator_dependency.pri
+++ b/tests/unit/unittest/creator_dependency.pri
@@ -14,7 +14,7 @@ include($$PWD/../../../src/plugins/clangrefactoring/clangrefactoring-source.pri)
 include($$PWD/../../../src/plugins/clangpchmanager/clangpchmanager-source.pri)
 include($$PWD/../../../src/plugins/cpptools/cpptoolsunittestfiles.pri)
 include(cplusplus.pri)
-!isEmpty(LLVM_INSTALL_DIR) {
+!isEmpty(LLVM_VERSION) {
 include($$PWD/../../../src/shared/clang/clang_defines.pri)
 include($$PWD/../../../src/tools/clangbackend/source/clangbackendclangipc-source.pri)
 include($$PWD/../../../src/plugins/clangcodemodel/clangcodemodelunittestfiles.pri)