Emit ´libtcg-helpers-$ARCH.bc`

Adds `llvm-helpers` subdir containing `to_bc.py` which converts all
input .c files to .bc using clang, and then llvm-links everything to a
single module.

Signed-off-by: Anton Johansson <anjo@rev.ng>

llvm-helpers/meson.build

+llvm_dep  = dependency('llvm', modules : ['support'])
+opt       = find_program(llvm_dep.get_variable(configtool: 'bindir') / 'opt')
+clang     = find_program(llvm_dep.get_variable(configtool: 'bindir') / 'clang')
+llvm_link = find_program(llvm_dep.get_variable(configtool: 'bindir') / 'llvm-link')
+
+to_ll = files('to_ll.py')

llvm-helpers/to_ll.py

+#!/usr/bin/env python3
+
+import argparse
+import json
+import os
+import shlex
+import sys
+import subprocess
+
+def run_command(argv):
+    proc = subprocess.Popen(argv)
+    if proc.wait() != 0:
+        print("Command exited with %d:\n%s\n" % (proc.returncode," ".join(argv)))
+
+def find_compile_commands(clang_path, input_path):
+    if os.path.exists("compile_commands.json"):
+        with open("compile_commands.json", "r") as compile_commands_file:
+            compile_commands = json.load(compile_commands_file)
+            for compile_command in compile_commands:
+                path = compile_command["file"]
+                #if os.path.basename(path) != os.path.basename(input_path):
+                if path != input_path:
+                    continue
+
+                os.chdir(compile_command["directory"])
+                command = compile_command["command"]
+                argv = shlex.split(command)
+                argv[0] = clang_path
+                return argv
+
+    # If we coulnd't find "compile_commands" just default
+    # to the following.
+    return [clang_path, input_path]
+
+def generate_llvm_ir(clang_path, input_path, output_path):
+    argv = find_compile_commands(clang_path, input_path)
+
+    for i, arg in reversed(list(enumerate(argv))):
+        if arg in {'-MQ', '-o', '-MF'}:
+            del argv[i:i+2]
+
+    argv += ["-Wno-unknown-warning-option",  "-emit-llvm", "-disable-O0-optnone -O0", "-o", output_path]
+
+    run_command(argv)
+
+def link(llvm_link_path, ll_paths, output_path):
+    argv = [llvm_link_path] + ll_paths + ['-o', output_path]
+    run_command(argv)
+
+def temp_file(file):
+    _, containing_folder = os.path.split(os.path.abspath(os.path.dirname(file)))
+    dir = os.path.join("llvm-helpers", containing_folder)
+    os.makedirs(dir, exist_ok=True)
+    filename, _ = os.path.splitext(os.path.basename(file))
+    new_file = os.path.join(dir, filename) + ".bc"
+    return new_file
+
+def main():
+    parser = argparse.ArgumentParser(description='Produce the LLVM IR for a given source file.')
+    parser.add_argument("clang",       metavar="CLANG_PATH",            help="Path to clang.")
+    parser.add_argument("llvm_link",   metavar="LLVM_LINK_PATH",        help="Path to llvm-link")
+    parser.add_argument("opt",         metavar="OPT_PATH",              help="Path to opt")
+    #parser.add_argument('passes',      metavar='LLVM_PASSES',           help='Path to library containing LLVM passes')
+    parser.add_argument('output',      metavar='OUTPUT_PATH',           help='Path to output file')
+    parser.add_argument('input_paths', metavar='INPUT_PATH', nargs='+', help='Source file input path')
+    args = parser.parse_args()
+
+    os.makedirs("llvm-helpers", exist_ok=True)
+
+    for input_path in args.input_paths:
+        print(input_path)
+
+    # Generate LLVM IR
+    ll_paths = []
+    for input_path in args.input_paths:
+        if input_path.endswith(".inc") or \
+           input_path.endswith(".h") or \
+           input_path.endswith(".pyinc") or \
+           input_path.endswith(".py") or \
+           "gdb" in input_path:
+            continue
+        output_path = temp_file(input_path)
+        ll_paths.append(output_path)
+        generate_llvm_ir(args.clang, input_path, output_path)
+
+    # Todo might be worth to have pre-pass that goes over module
+    # and checks if it contains any attribute we care about.
+    # We could then reject the entire module if not.
+    #
+    # Profile this!
+
+    # link together llvm-ir
+    link(args.llvm_link, ll_paths, args.output)
+
+    #step1_out = temp_file("step1")
+    #command = [
+    #    args.opt,
+    #    '-enable-new-pm=0',
+    #    '-load',
+    #    args.passes,
+    #    ll_out,
+    #    '--TagHelpersPass',
+    #    '-S',
+    #    '-o',
+    #    step1_out
+    #]
+
+    #print(" ".join(command))
+
+    #proc = subprocess.Popen(command)
+    #if proc.wait() != 0:
+    #    print("Command: %s exited with %d\n" % (" ".join(command), proc.returncode))
+
+    #proc = subprocess.Popen([args.clang, '-c', step1_out, '-o', args.output])
+    #if proc.wait() != 0:
+    #    print("#lol")
+
+if __name__ == "__main__":
+    sys.exit(main())