When compiling, use a single clang command for all input sources. NFC (#20713)

For folks that compiler a bunch of source files at once which should
help by reducing the number of clang subprocesses that we spawn.  This
includes the new system library build process that we use internally.
See #20577.

Do the same for PCH compilation and pre-processing (-E).

Author: sbc100

emcc.py

@@ -1332,9 +1332,6 @@ def run(args):
     logger.debug('stopping after compile phase')
     for flag in state.link_flags:
       diagnostics.warning('unused-command-line-argument', "argument unused during compilation: '%s'" % flag[1])
-    for f in linker_inputs:
-      diagnostics.warning('unused-command-line-argument', "%s: linker input file unused because linking not done" % f[1])
-
     return 0
 
   # We have now passed the compile phase, allow reading/writing of all settings.
@@ -1627,8 +1624,6 @@ def phase_setup(options, state, newargs):
     elif '-M' in newargs or '-MM' in newargs:
       options.default_object_extension = '.mout' # not bitcode, not js; but just dependency rule of the input file
 
-    if options.output_file and len(input_files) > 1:
-      exit_with_error('cannot specify -o with -c/-S/-E/-M and multiple source files')
   else:
     for arg in state.orig_args:
       if any(arg.startswith(f) for f in COMPILE_ONLY_FLAGS):
@@ -3030,6 +3025,19 @@ def get_full_import_name(name):
   return target, wasm_target
 
 
+def get_clang_output_extension(state):
+  if '-emit-llvm' in state.orig_args:
+    if state.has_dash_S:
+      return '.ll'
+    else:
+      return '.bc'
+
+  if state.has_dash_S:
+    return '.s'
+  else:
+    return '.o'
+
+
 @ToolchainProfiler.profile_block('compile inputs')
 def phase_compile_inputs(options, state, newargs, input_files):
   def is_link_flag(flag):
@@ -3064,40 +3072,62 @@ def get_language_mode(args):
   language_mode = get_language_mode(newargs)
   use_cxx = 'c++' in language_mode or run_via_emxx
 
-  def get_clang_command(src_file):
-    return compiler + get_cflags(state.orig_args, use_cxx) + compile_args + [src_file]
+  def get_clang_command():
+    return compiler + get_cflags(state.orig_args, use_cxx) + compile_args
 
-  def get_clang_command_preprocessed(src_file):
-    return compiler + get_clang_flags(state.orig_args) + compile_args + [src_file]
+  def get_clang_command_preprocessed():
+    return compiler + get_clang_flags(state.orig_args) + compile_args
 
-  def get_clang_command_asm(src_file):
-    return compiler + get_target_flags() + compile_args + [src_file]
+  def get_clang_command_asm():
+    return compiler + get_target_flags() + compile_args
 
   # preprocessor-only (-E) support
   if state.mode == Mode.PREPROCESS_ONLY:
-    for input_file in [x[1] for x in input_files]:
-      cmd = get_clang_command(input_file)
-      if options.output_file:
-        cmd += ['-o', options.output_file]
-      # Do not compile, but just output the result from preprocessing stage or
-      # output the dependency rule. Warning: clang and gcc behave differently
-      # with -MF! (clang seems to not recognize it)
-      logger.debug(('just preprocessor ' if state.has_dash_E else 'just dependencies: ') + ' '.join(cmd))
-      shared.check_call(cmd)
+    inputs = [i[1] for i in input_files]
+    cmd = get_clang_command() + inputs
+    if options.output_file:
+      cmd += ['-o', options.output_file]
+    # Do not compile, but just output the result from preprocessing stage or
+    # output the dependency rule. Warning: clang and gcc behave differently
+    # with -MF! (clang seems to not recognize it)
+    logger.debug(('just preprocessor ' if state.has_dash_E else 'just dependencies: ') + ' '.join(cmd))
+    shared.check_call(cmd)
     return []
 
   # Precompiled headers support
   if state.mode == Mode.PCH:
-    headers = [header for _, header in input_files]
-    for header in headers:
+    inputs = [i[1] for i in input_files]
+    for header in inputs:
       if not shared.suffix(header) in HEADER_ENDINGS:
-        exit_with_error(f'cannot mix precompiled headers with non-header inputs: {headers} : {header}')
-      cmd = get_clang_command(header)
-      if options.output_file:
-        cmd += ['-o', options.output_file]
-      logger.debug(f"running (for precompiled headers): {cmd[0]} {' '.join(cmd[1:])}")
-      shared.check_call(cmd)
-      return []
+        exit_with_error(f'cannot mix precompiled headers with non-header inputs: {inputs} : {header}')
+    cmd = get_clang_command() + inputs
+    if options.output_file:
+      cmd += ['-o', options.output_file]
+    logger.debug(f"running (for precompiled headers): {cmd[0]} {' '.join(cmd[1:])}")
+    shared.check_call(cmd)
+    return []
+
+  if state.mode == Mode.COMPILE_ONLY:
+    inputs = [i[1] for i in input_files]
+    if all(get_file_suffix(i) in ASSEMBLY_ENDINGS for i in inputs):
+      cmd = get_clang_command_asm() + inputs
+    else:
+      cmd = get_clang_command() + inputs
+    if options.output_file:
+      cmd += ['-o', options.output_file]
+      if get_file_suffix(options.output_file) == '.bc' and not settings.LTO and '-emit-llvm' not in state.orig_args:
+        diagnostics.warning('emcc', '.bc output file suffix used without -flto or -emit-llvm.  Consider using .o extension since emcc will output an object file, not a bitcode file')
+    shared.check_call(cmd)
+    if not options.output_file:
+      # Rename object files to match --default-obj-ext
+      # TODO: Remove '--default-obj-ext' to reduce this complexity
+      ext = get_clang_output_extension(state)
+      if options.default_object_extension != ext:
+        for i in inputs:
+          output = unsuffixed_basename(i) + ext
+          new_output = unsuffixed_basename(i) + options.default_object_extension
+          move_file(output, new_output)
+    return []
 
   linker_inputs = []
   seen_names = {}
@@ -3108,32 +3138,21 @@ def uniquename(name):
     return unsuffixed(name) + '_' + seen_names[name] + shared.suffix(name)
 
   def get_object_filename(input_file):
-    if state.mode == Mode.COMPILE_ONLY:
-      # In compile-only mode we don't use any temp file.  The object files
-      # are written directly to their final output locations.
-      if options.output_file:
-        assert len(input_files) == 1
-        if get_file_suffix(options.output_file) == '.bc' and not settings.LTO and '-emit-llvm' not in state.orig_args:
-          diagnostics.warning('emcc', '.bc output file suffix used without -flto or -emit-llvm.  Consider using .o extension since emcc will output an object file, not a bitcode file')
-        return options.output_file
-      else:
-        return unsuffixed_basename(input_file) + options.default_object_extension
-    else:
-      return in_temp(unsuffixed(uniquename(input_file)) + options.default_object_extension)
+    return in_temp(unsuffixed(uniquename(input_file)) + options.default_object_extension)
 
   def compile_source_file(i, input_file):
     logger.debug(f'compiling source file: {input_file}')
     output_file = get_object_filename(input_file)
-    if state.mode not in (Mode.COMPILE_ONLY, Mode.PREPROCESS_ONLY):
-      linker_inputs.append((i, output_file))
+    linker_inputs.append((i, output_file))
     if get_file_suffix(input_file) in ASSEMBLY_ENDINGS:
-      cmd = get_clang_command_asm(input_file)
+      cmd = get_clang_command_asm()
     elif get_file_suffix(input_file) in PREPROCESSED_ENDINGS:
-      cmd = get_clang_command_preprocessed(input_file)
+      cmd = get_clang_command_preprocessed()
     else:
-      cmd = get_clang_command(input_file)
+      cmd = get_clang_command()
       if get_file_suffix(input_file) in ['.pcm']:
         cmd = [c for c in cmd if not c.startswith('-fprebuilt-module-path=')]
+    cmd += [input_file]
     if not state.has_dash_c:
       cmd += ['-c']
     cmd += ['-o', output_file]

test/test_other.py

@@ -589,7 +589,7 @@ def test_multiple_sources(self):
     self.clear()
     err = self.expect_fail(cmd + ['-o', 'out.o'])
 
-    self.assertContained('cannot specify -o with -c/-S/-E/-M and multiple source files', err)
+    self.assertContained('clang: error: cannot specify -o when generating multiple output files', err)
     self.assertNotExists('twopart_main.o')
     self.assertNotExists('twopart_side.o')
     self.assertNotExists(test_file('twopart_main.o'))
@@ -5280,10 +5280,11 @@ def test_dashS_stdout(self):
     self.assertEqual(os.listdir('.'), [])
     self.assertContained('hello_world.c', stdout)
 
-  def test_emit_llvm(self):
+  def test_emit_llvm_asm(self):
     self.run_process([EMCC, test_file('hello_world.c'), '-S', '-emit-llvm'])
     self.assertIsLLVMAsm('hello_world.ll')
 
+  def test_emit_llvm(self):
     self.run_process([EMCC, test_file('hello_world.c'), '-c', '-emit-llvm'])
     self.assertTrue(building.is_bitcode('hello_world.bc'))
 
@@ -11414,7 +11415,7 @@ def test_linker_flags_unused(self):
   def test_linker_input_unused(self):
     self.run_process([EMXX, '-c', test_file('hello_world.cpp')])
     err = self.run_process([EMCC, 'hello_world.o', '-c', '-o', 'out.o'], stderr=PIPE).stderr
-    self.assertContained("warning: hello_world.o: linker input file unused because linking not done [-Wunused-command-line-argument", err)
+    self.assertContained("clang: warning: hello_world.o: 'linker' input unused [-Wunused-command-line-argument]", err)
     # In this case the compiler does not produce any output file.
     self.assertNotExists('out.o')