add an alloy.py option to build ispc binary with g++

alloy.py

@@ -239,7 +239,7 @@ def check_targets():
     answer_sde = []
     # check what native targets do we have
     if current_OS != "Windows":
-        try_do_LLVM("build check_ISA", "clang check_isa.cpp -o check_isa.exe", True)
+        try_do_LLVM("build check_ISA", "g++ check_isa.cpp -o check_isa.exe", True)
     else:
         try_do_LLVM("build check_ISA", "cl check_isa.cpp", True)
     SSE2  = ["sse2-i32x4",  "sse2-i32x8"]
@@ -296,6 +296,18 @@ def check_targets():
 def build_ispc(version_LLVM, make):
     current_path = os.getcwd()
     os.chdir(os.environ["ISPC_HOME"])
+
+    # the default 'make' variable for ISPC and LLVM may be actually different,
+    # so we have to manually set a new make command here (make targets are already verified in Main() )
+    if (options.ispc_compiler == "clang"):
+        make_target = "clang"
+    elif (options.ispc_compiler == "gcc"):
+        make_target = "gcc"
+    elif (options.ispc_compiler == "g++"):
+        make_target = "gcc"
+
+    make_ispc = "make " + make_target + " -j" + options.speed
+
     if current_OS != "Windows":
         p_temp = os.getenv("PATH")
         os.environ["PATH"] = os.environ["LLVM_HOME"] + "/bin-" + version_LLVM + "/bin:" + os.environ["PATH"]
@@ -312,7 +324,7 @@ def build_ispc(version_LLVM, make):
         (revision_llvm, err) = p.communicate()
         
         try_do_LLVM("recognize LLVM revision", "svn info " + folder, True)
-        try_do_LLVM("build ISPC with LLVM version " + version_LLVM + " ", make, True)
+        try_do_LLVM("build ISPC with LLVM version " + version_LLVM + " ", make_ispc, True)
         os.environ["PATH"] = p_temp
     else:
         p_temp = os.getenv("LLVM_INSTALL_DIR")
@@ -650,6 +662,19 @@ def Main():
         parser.print_help()
         exit(0)
 
+    # set appropriate makefile target
+    # gcc and g++ options are equal and added for ease of use 
+    if (options.ispc_compiler == "clang"):
+        make_target = "clang"
+    elif (options.ispc_compiler == "gcc"):
+        make_target = "gcc"
+    elif (options.ispc_compiler == "g++"):
+        make_target = "gcc"
+    else:
+        error("unknow option for --ispc-compiler: " + options.ispc_compiler, 1)
+        parser.print_help()
+        exit(0)
+
     setting_paths(options.llvm_home, options.ispc_home, options.sde_home)
     if os.environ.get("LLVM_HOME") == None:
         error("you have no LLVM_HOME", 1)
@@ -759,6 +784,8 @@ if __name__ == '__main__':
         help='ask for validation run', default=False, action="store_true")
     parser.add_option('-j', dest='speed',
         help='set -j for make', default=num_threads)
+    parser.add_option('--ispc-compiler', dest='ispc_compiler',
+        help='set compiler to build ispc binary (clang or g++)', default="clang")
     # options for activity "build LLVM"
     llvm_group = OptionGroup(parser, "Options for building LLVM",
                     "These options must be used with -b option.")