Bug 1501796 - Add USE_NASM mozbuild option. r=firefox-build-system-reviewers,mshal

Differential Revision: https://phabricator.services.mozilla.com/D9868

--HG--
extra : moz-landing-system : lando

python/mozbuild/mozbuild/frontend/context.py

@@ -372,6 +372,12 @@ class AsmFlags(BaseCompileFlags):
                     debug_flags += ['-g', 'cv8']
                 elif self._context.config.substs.get('OS_ARCH') != 'Darwin':
                     debug_flags += ['-g', 'dwarf2']
+            elif self._context.get('USE_NASM'):
+                if (self._context.config.substs.get('OS_ARCH') == 'WINNT' and
+                    not self._context.config.substs.get('GNU_CC')):
+                    debug_flags += ['-F', 'cv8']
+                elif self._context.config.substs.get('OS_ARCH') != 'Darwin':
+                    debug_flags += ['-F', 'dwarf']
             elif (self._context.config.substs.get('OS_ARCH') == 'WINNT' and
                   self._context.config.substs.get('CPU_ARCH') == 'aarch64'):
                 # armasm64 accepts a paucity of options compared to ml/ml64.
@@ -2143,6 +2149,17 @@ VARIABLES = {
         corresponding XPCOMBinaryComponent.
         """),
 
+    'USE_NASM': (bool, bool,
+        """Use the nasm assembler to assemble assembly files from SOURCES.
+
+        By default, the build will use the toolchain assembler, $(AS), to
+        assemble source files in assembly language (.s or .asm files). Setting
+        this value to ``True`` will cause it to use nasm instead.
+
+        If nasm is not available on this system, or does not support the
+        current target architecture, an error will be raised.
+        """),
+
     'USE_YASM': (bool, bool,
         """Use the yasm assembler to assemble assembly files from SOURCES.
 

python/mozbuild/mozbuild/frontend/emitter.py

@@ -1322,6 +1322,15 @@ class TreeMetadataEmitter(LoggingMixin):
         computed_as_flags.resolve_flags('MOZBUILD',
                                         context.get('ASFLAGS'))
 
+        if context.get('USE_NASM') is True:
+            nasm = context.config.substs.get('NASM')
+            if not nasm:
+                raise SandboxValidationError('nasm is not available', context)
+            passthru.variables['AS'] = nasm
+            passthru.variables['AS_DASH_C_FLAG'] = ''
+            passthru.variables['ASOUTOPTION'] = '-o '
+            computed_as_flags.resolve_flags('OS',
+                                            context.config.substs.get('NASM_ASFLAGS', []))
         if context.get('USE_YASM') is True:
             yasm = context.config.substs.get('YASM')
             if not yasm: