diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 433af900dd2..ad9a2432dbf 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -24,6 +24,23 @@ endif()
 
 include(FindPythonInterp)
 if(PYTHONINTERP_FOUND)
+  get_directory_property(DEFINITIONS COMPILE_DEFINITIONS)
+  foreach(DEF ${DEFINITIONS})
+    set(DEFS "${DEFS} -D${DEF}")
+  endforeach()
+  get_directory_property(INC_DIRS INCLUDE_DIRECTORIES)
+  foreach(INC_DIR ${INC_DIRS})
+    set(IDIRS "${IDIRS} -I${INC_DIR}")
+  endforeach()
+  string(REPLACE "<CMAKE_CXX_COMPILER>" "${CMAKE_CXX_COMPILER}" TEST_COMPILE_CXX_CMD ${CMAKE_CXX_COMPILE_OBJECT})
+  string(REPLACE "<DEFINES>"            "${DEFS}"               TEST_COMPILE_CXX_CMD ${TEST_COMPILE_CXX_CMD})
+  string(REPLACE "<FLAGS>"              "${CMAKE_CXX_FLAGS}"    TEST_COMPILE_CXX_CMD ${TEST_COMPILE_CXX_CMD})
+  string(REPLACE "-o"                   ""                      TEST_COMPILE_CXX_CMD ${TEST_COMPILE_CXX_CMD})
+  string(REGEX REPLACE "<[^>]+>"        ""                      TEST_COMPILE_CXX_CMD ${TEST_COMPILE_CXX_CMD})
+  set(TEST_COMPILE_CXX_CMD "${TEST_COMPILE_CXX_CMD} ${IDIRS}")
+  if(NOT MSVC)
+    set(TEST_COMPILE_CXX_CMD "${TEST_COMPILE_CXX_CMD} -x c++")
+  endif()
   configure_file(
     ${CMAKE_CURRENT_SOURCE_DIR}/site.exp.in
     ${CMAKE_CURRENT_BINARY_DIR}/site.exp)
diff --git a/test/LLVMC/Alias.td b/test/LLVMC/Alias.td
index 88e142dae27..5d37889304b 100644
--- a/test/LLVMC/Alias.td
+++ b/test/LLVMC/Alias.td
@@ -1,7 +1,7 @@
 // Test alias generation.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
 // RUN: FileCheck -input-file %t %s
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/AppendCmdHook.td b/test/LLVMC/AppendCmdHook.td
index 690ece779df..c85f002e6e8 100644
--- a/test/LLVMC/AppendCmdHook.td
+++ b/test/LLVMC/AppendCmdHook.td
@@ -1,7 +1,7 @@
 // Check that hooks can be invoked from 'append_cmd'.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
 // RUN: FileCheck -input-file %t %s
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/EmptyCompilationGraph.td b/test/LLVMC/EmptyCompilationGraph.td
index 3d2210a0fff..a52b8a8c199 100644
--- a/test/LLVMC/EmptyCompilationGraph.td
+++ b/test/LLVMC/EmptyCompilationGraph.td
@@ -1,6 +1,6 @@
 // Check that the compilation graph can be empty.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/EnvParentheses.td b/test/LLVMC/EnvParentheses.td
index 403beb9521f..ce0cb824604 100644
--- a/test/LLVMC/EnvParentheses.td
+++ b/test/LLVMC/EnvParentheses.td
@@ -2,7 +2,7 @@
 // http://llvm.org/bugs/show_bug.cgi?id=4157
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
 // RUN: not grep {FOO")));} %t
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/ForwardAs.td b/test/LLVMC/ForwardAs.td
index 326e94b0e86..99b240e30fb 100644
--- a/test/LLVMC/ForwardAs.td
+++ b/test/LLVMC/ForwardAs.td
@@ -2,7 +2,7 @@
 // http://llvm.org/bugs/show_bug.cgi?id=4159
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
 // RUN: FileCheck -input-file %t %s
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/ForwardTransformedValue.td b/test/LLVMC/ForwardTransformedValue.td
index 10038f68d3e..9184ede3610 100644
--- a/test/LLVMC/ForwardTransformedValue.td
+++ b/test/LLVMC/ForwardTransformedValue.td
@@ -2,7 +2,7 @@
 // The dummy tool and graph are required to silence warnings.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
 // RUN: FileCheck -input-file %t %s
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/ForwardValue.td b/test/LLVMC/ForwardValue.td
index 402fa50f7a2..a42a3f06ec3 100644
--- a/test/LLVMC/ForwardValue.td
+++ b/test/LLVMC/ForwardValue.td
@@ -2,7 +2,7 @@
 // The dummy tool and graph are required to silence warnings.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
 // RUN: FileCheck -input-file %t %s
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/HookWithArguments.td b/test/LLVMC/HookWithArguments.td
index b3260a973b8..bbba2e98459 100644
--- a/test/LLVMC/HookWithArguments.td
+++ b/test/LLVMC/HookWithArguments.td
@@ -1,7 +1,7 @@
 // Check that hooks with arguments work.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
 // RUN: FileCheck -input-file %t %s
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/HookWithInFile.td b/test/LLVMC/HookWithInFile.td
index cc5da43b663..ed08b5321cc 100644
--- a/test/LLVMC/HookWithInFile.td
+++ b/test/LLVMC/HookWithInFile.td
@@ -1,7 +1,7 @@
 // Check that a hook can be given $INFILE as an argument.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
 // RUN: FileCheck -input-file %t %s
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/Init.td b/test/LLVMC/Init.td
index 8ab07d880b4..c3846797026 100644
--- a/test/LLVMC/Init.td
+++ b/test/LLVMC/Init.td
@@ -1,7 +1,7 @@
 // Check that (init true/false) and (init "str") work.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
 // RUN: FileCheck -input-file %t %s
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/LanguageMap.td b/test/LLVMC/LanguageMap.td
index aa1149ca7f0..a0502142e6d 100644
--- a/test/LLVMC/LanguageMap.td
+++ b/test/LLVMC/LanguageMap.td
@@ -1,7 +1,7 @@
 // Check that LanguageMap is processed properly.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
 // RUN: FileCheck -input-file %t %s
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/MultiValuedOption.td b/test/LLVMC/MultiValuedOption.td
index b6da6ce4c1d..08c753380d4 100644
--- a/test/LLVMC/MultiValuedOption.td
+++ b/test/LLVMC/MultiValuedOption.td
@@ -2,7 +2,7 @@
 // The dummy tool and graph are required to silence warnings.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
 // RUN: FileCheck -input-file %t %s
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/MultipleCompilationGraphs.td b/test/LLVMC/MultipleCompilationGraphs.td
index 0eaad872a71..b3746c03b6c 100644
--- a/test/LLVMC/MultipleCompilationGraphs.td
+++ b/test/LLVMC/MultipleCompilationGraphs.td
@@ -1,6 +1,6 @@
 // Check that multiple compilation graphs are allowed.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/NoActions.td b/test/LLVMC/NoActions.td
index 2573fbe2f2c..34b44406635 100644
--- a/test/LLVMC/NoActions.td
+++ b/test/LLVMC/NoActions.td
@@ -1,7 +1,7 @@
 // Check that tools without associated actions are accepted.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
 // RUN: FileCheck -input-file %t %s
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/NoCompilationGraph.td b/test/LLVMC/NoCompilationGraph.td
index 1208f2c5f07..4182882c451 100644
--- a/test/LLVMC/NoCompilationGraph.td
+++ b/test/LLVMC/NoCompilationGraph.td
@@ -1,6 +1,6 @@
 // Check that the compilation graph is not required.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/OneOrMore.td b/test/LLVMC/OneOrMore.td
index bb0ad8b11b1..54fa62d1ff0 100644
--- a/test/LLVMC/OneOrMore.td
+++ b/test/LLVMC/OneOrMore.td
@@ -2,7 +2,7 @@
 // The dummy tool and graph are required to silence warnings.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
 // RUN: FileCheck -input-file %t %s
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/OptionPreprocessor.td b/test/LLVMC/OptionPreprocessor.td
index 556530b8f76..8019c42634f 100644
--- a/test/LLVMC/OptionPreprocessor.td
+++ b/test/LLVMC/OptionPreprocessor.td
@@ -1,7 +1,7 @@
 // Test for the OptionPreprocessor and related functionality.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
 // RUN: FileCheck -input-file %t %s
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/LLVMC/OutputSuffixHook.td b/test/LLVMC/OutputSuffixHook.td
index 6bb2866c38b..1f5ecd1237f 100644
--- a/test/LLVMC/OutputSuffixHook.td
+++ b/test/LLVMC/OutputSuffixHook.td
@@ -1,7 +1,7 @@
 // Check that hooks can be invoked from 'output_suffix'.
 // RUN: tblgen -I %p/../../include --gen-llvmc %s -o %t
 // RUN: FileCheck -input-file %t %s
-// RUN: %compile_cxx -x c++ %t
+// RUN: %compile_cxx %t
 // XFAIL: vg_leak
 
 include "llvm/CompilerDriver/Common.td"
diff --git a/test/Makefile b/test/Makefile
index 1e179da008a..5bec0eb7ad5 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -145,8 +145,8 @@ site.exp: FORCE
 	@echo 'set objdir "$(LLVM_OBJ_ROOT)/test"' >>site.tmp
 	@echo 'set gccpath "$(CC)"' >>site.tmp
 	@echo 'set gxxpath "$(CXX)"' >>site.tmp
-	@echo 'set compile_c "' $(CC) $(CPP.Flags) $(TargetCommonOpts) $(CompileCommonOpts) -c '"' >>site.tmp
-	@echo 'set compile_cxx "' $(CXX) $(CPP.Flags) $(CXX.Flags) $(TargetCommonOpts) $(CompileCommonOpts) -c '"' >> site.tmp
+	@echo 'set compile_c "' $(CC) $(CPP.Flags) $(TargetCommonOpts) $(CompileCommonOpts) -c -x c '"' >>site.tmp
+	@echo 'set compile_cxx "' $(CXX) $(CPP.Flags) $(CXX.Flags) $(TargetCommonOpts) $(CompileCommonOpts) -c -x c++ '"' >> site.tmp
 	@echo 'set link "' $(CXX) $(CPP.Flags) $(CXX.Flags) $(TargetCommonOpts) $(CompileCommonOpts) $(LD.Flags) '"' >>site.tmp
 	@echo 'set llvmgcc "$(LLVMGCC) $(TargetCommonOpts) $(EXTRA_OPTIONS)"' >> site.tmp
 	@echo 'set llvmgxx "$(LLVMGCC) $(TargetCommonOpts) $(EXTRA_OPTIONS)"' >> site.tmp
diff --git a/test/lit.cfg b/test/lit.cfg
index 28f336ba20c..f15777c9991 100644
--- a/test/lit.cfg
+++ b/test/lit.cfg
@@ -49,6 +49,14 @@ if llvm_obj_root is not None:
 if 'HOME' in os.environ:
     config.environment['HOME'] = os.environ['HOME']
 
+# Propogate 'INCLUDE' through the environment.
+if 'INCLUDE' in os.environ:
+    config.environment['INCLUDE'] = os.environ['INCLUDE']
+
+# Propogate 'LIB' through the environment.
+if 'LIB' in os.environ:
+    config.environment['LIB'] = os.environ['LIB']
+
 # Propogate LLVM_SRC_ROOT into the environment.
 config.environment['LLVM_SRC_ROOT'] = getattr(config, 'llvm_src_root', '')