Emscripten: Add wasm64 target #927
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MEMORY64 enables 64bit pointers so this commit updates the accessors for the libffi data structures accordingly. Each JS functions in ffi.c receives pointers as BigInt (i64) values and with casts them to Numer (i53) using bigintToI53Checked. While memory64 supports 64bit addressing, the maximum memory size is currently limited to 16GiB [1]. Therefore, we can assume that the passed pointers are within the Number's range. [1] https://webassembly.github.io/memory64/js-api/#limits Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
This commit adds support for the wasm64 target via the configure script. Emscripten supports two modes of the -sMEMORY64 flag[1] so the script allows users specifying the value through a configuration variable. Additionally, "src/wasm32" directory has been renamed to the more generic "src/wasm" because it's now shared between both 32bit and 64bit builds. [1] https://emscripten.org/docs/tools_reference/settings_reference.html#memory64 Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
This commit adds a test matrix for wasm32, wasm64 and wasm64 with the -sMEMORY64=2 flag, using the latest version of Emscripten. -Wno-main is added to suppress the following warning in unwindtest.cc and unwindtest_ffi_call.cc. > FAIL: libffi.closures/unwindtest_ffi_call.cc -W -Wall -O2 (test for excess errors) > Excess errors: > ./libffi.closures/unwindtest_ffi_call.cc:20:5: warning: 'main' should not be 'extern "C"' [-Wmain] > 20 | int main (void) > | ^ > 1 warning generated. Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
test_libffi.py calls each test's main function without arguments, but some tests define the main function with parameters. This signature mismatch causes a runtime error with the recent version of Emscripten. This commit resolves this issue by updating the function signatures to match the way they are called. Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
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LGTM! In Emscripten, we usually use #ifdef __wasm64__ and #ifdef __wasm32__ for these checks, but I like this approach as well.
It also makes me wonder if we could rely more on the __SIZEOF_*__ macros instead of using hardcoded values (and perhaps use something like #define FFI_ALIGNOF(type) _Alignof(type)?), but that be done as a possible follow-up.
@hoodmane Would you like to review this as well?
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Thank you for your review, @kleisauke ! |
| # TODO: node-based tests of wasm64 requires newer version of node (v23.0.0) | ||
| # which isn't available on the current emsdk. |
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Use an action to install node 24?
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We shouldn't use the node from emsdk anyways.
| @@ -123,6 +123,8 @@ AC_C_BIGENDIAN | |||
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| GCC_AS_CFI_PSEUDO_OP | |||
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| AC_ARG_VAR([WASM64_MEMORY64], [Used only for the wasm64 target. Set to 1 (default) or 2 for Emscripten's -sMEMORY64 mode]) | |||
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What's the difference between these?
| var struct_arg_info = []; | ||
| for (var i = nargs - 1; i >= nfixedargs; i--) { | ||
| var arg_ptr = DEREF_U32(avalue, i); | ||
| var arg_unboxed = unbox_small_structs(DEREF_U32(arg_types_ptr, i)); | ||
| var arg_ptr = DEC_PTR(DEREF_PTR(avalue, i)); |
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Maybe we could use a macro for DEC_PTR(DEREF_PTR(x))?
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Code looks good to me. In a few places the formatting could be improved, and it might be nice to add more macros for common patterns. But I would be fine with merging as-is as well, other than adding a test with node 24. |
This PR adds support for building libffi with Emscripten's -sMEMORY64 flag.
A new
wasm64target is introduced in the build scripts. When this is selected, the-sMEMORY64=1flag is automatically passed to emcc, enabling 64bit addressing.Emscripten's
-sMEMORY64has another mode (-sMEMORY64=2) which allows the 64bit code to run on wasm32 engines. To enable this mode, WASM64_MEMORY64 variable can be used.