Bug 1867845 - Split rlbox.wasm.c in multiple parts in local builds. r=firefox-build-system-reviewers,sergesanspaille

We pick an arbitrary number of files to split the wasm2c output.

Differential Revision: https://phabricator.services.mozilla.com/D195276

config/wasm2c.py

@@ -6,9 +6,9 @@ import os
 import subprocess
 
 
-def wasm2c(output, wasm2c_bin, wasm_lib):
+def wasm2c(output, wasm2c_bin, wasm_lib, *flags):
     output.close()
     module_name = os.path.basename(os.path.splitext(wasm_lib)[0])
     return subprocess.run(
-        [wasm2c_bin, "-n", module_name, "-o", output.name, wasm_lib]
+        [wasm2c_bin, "-n", module_name] + list(flags) + ["-o", output.name, wasm_lib]
     ).returncode

security/rlbox/rlbox.mozbuild

@@ -12,7 +12,11 @@ def RLBoxLibrary(name, use_segue=True):
         "/third_party/rlbox_wasm2c_sandbox/c_src/wasm2c_sandbox_wrapper.c",
     ]
 
-    SOURCES += [f"!{name}.wasm.c"]
+    if CONFIG["DEVELOPER_OPTIONS"]:
+        wasm_sources = sorted(f"!{name}.wasm_{n}.c" for n in range(16))
+    else:
+        wasm_sources = [f"!{name}.wasm.c"]
+    SOURCES += wasm_sources
     SOURCES += ["/third_party/wasm2c/wasm2c/wasm-rt-impl.c"]
     SOURCES += ["/third_party/wasm2c/wasm2c/wasm-rt-mem-impl.c"]
 
@@ -38,9 +42,8 @@ def RLBoxLibrary(name, use_segue=True):
     # fails inside the sandbox. This information is used to annotate crash reports.
     DEFINES["WASM_RT_GROW_FAILED_HANDLER"] = "moz_wasm2c_memgrow_failed"
 
-    SOURCES[f"!{name}.wasm.c"].flags += [
-        "-Wno-unused",
-    ]
+    for source in wasm_sources:
+        SOURCES[source].flags += ["-Wno-unused"]
 
     # Use Segue optimization. Since this requires passing the "-mfsgsbase", we
     # restrict this to compilers and architectures that support this flag.
@@ -81,4 +84,5 @@ def RLBoxLibrary(name, use_segue=True):
         script="/config/wasm2c.py",
         entry_point="wasm2c",
         inputs=["!/dist/host/bin/wasm2c" + CONFIG["HOST_BIN_SUFFIX"], f"!{name}.wasm"],
+        flags=["--num-outputs", len(wasm_sources)] if len(wasm_sources) > 1 else [],
     )