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[PATCH 2/4] configure: Enable to propagate -sMEMORY64 flag to Emscripten

Kohei Tokunaga posted 4 patches 4 months, 1 week ago
Maintainers: "Alex Bennée" <alex.bennee@linaro.org>, "Philippe Mathieu-Daudé" <philmd@linaro.org>, Thomas Huth <thuth@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, "Marc-André Lureau" <marcandre.lureau@redhat.com>, "Daniel P. Berrangé" <berrange@redhat.com>, Kohei Tokunaga <ktokunaga.mail@gmail.com>
There is a newer version of this series
[PATCH 2/4] configure: Enable to propagate -sMEMORY64 flag to Emscripten
Posted by Kohei Tokunaga 4 months, 1 week ago 
Currently there are some engines that don't support wasm64 (e.g. unsupported
on Safari[1]). To mitigate this issue, the configure script allows the user
to use Emscripten's compatibility feature, "-sMEMORY64=2" flag[2].

Emscripten's "-sMEMORY64=2" flag still enables 64bit pointers in C code. But
this flag lowers the output binary into wasm32, with limiting the maximum
memory size to 4GB. So QEMU can run on wasm32 engines.

This commit adds "--wasm64-memory64" flag to the configure script. This
takes the value to propagate to Emscripten's -sMEMORY64. 1(default) targets
wasm64 engines and 2 targets wasm32 engines with still enabling 64bit
pointers.

[1] https://webassembly.org/features/
[2] https://emscripten.org/docs/tools_reference/settings_reference.html#memory64

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
---
 configure | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index 7f3893a42f..8573f84e26 100755
--- a/configure
+++ b/configure
@@ -182,6 +182,8 @@ EXTRA_CXXFLAGS=""
 EXTRA_OBJCFLAGS=""
 EXTRA_LDFLAGS=""
 
+wasm64_memory64=1
+
 # Default value for a variable defining feature "foo".
 #  * foo="no"  feature will only be used if --enable-foo arg is given
 #  * foo=""    feature will be searched for, and if found, will be used
@@ -239,6 +241,8 @@ for opt do
   ;;
   --without-default-features) default_feature="no"
   ;;
+  --wasm64-memory64=*) wasm64_memory64="$optarg"
+  ;;
   esac
 done
 
@@ -537,7 +541,7 @@ case "$cpu" in
     CPU_CFLAGS="-m32"
     ;;
   wasm64)
-    CPU_CFLAGS="-m64 -sMEMORY64=1"
+    CPU_CFLAGS="-m64 -sMEMORY64=$wasm64_memory64"
     ;;
 esac
 
@@ -795,6 +799,8 @@ for opt do
   ;;
   --disable-rust) rust=disabled
   ;;
+  --wasm64-memory64=*)
+  ;;
   # everything else has the same name in configure and meson
   --*) meson_option_parse "$opt" "$optarg"
   ;;
@@ -920,6 +926,8 @@ Advanced options (experts only):
   --disable-containers     don't use containers for cross-building
   --container-engine=TYPE  which container engine to use [$container_engine]
   --gdb=GDB-path           gdb to use for gdbstub tests [$gdb_bin]
+  --wasm64-memory64        Used only for wasm64 build. Set -sMEMORY64 of
+                           Emscripten to 1(default) or 2 (choices: 1/2)
 EOF
   meson_options_help
 cat << EOF
-- 
2.43.0
Re: [PATCH 2/4] configure: Enable to propagate -sMEMORY64 flag to Emscripten
Posted by Philippe Mathieu-Daudé 4 months, 1 week ago 
Hi Kohei,

On 4/8/25 14:57, Kohei Tokunaga wrote:
> Currently there are some engines that don't support wasm64 (e.g. unsupported
> on Safari[1]). To mitigate this issue, the configure script allows the user
> to use Emscripten's compatibility feature, "-sMEMORY64=2" flag[2].
> 
> Emscripten's "-sMEMORY64=2" flag still enables 64bit pointers in C code. But
> this flag lowers the output binary into wasm32, with limiting the maximum
> memory size to 4GB. So QEMU can run on wasm32 engines.
> 
> This commit adds "--wasm64-memory64" flag to the configure script. This
> takes the value to propagate to Emscripten's -sMEMORY64. 1(default) targets
> wasm64 engines and 2 targets wasm32 engines with still enabling 64bit
> pointers.
> 
> [1] https://webassembly.org/features/
> [2] https://emscripten.org/docs/tools_reference/settings_reference.html#memory64
> 
> Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
> ---
>   configure | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/configure b/configure
> index 7f3893a42f..8573f84e26 100755
> --- a/configure
> +++ b/configure
> @@ -182,6 +182,8 @@ EXTRA_CXXFLAGS=""
>   EXTRA_OBJCFLAGS=""
>   EXTRA_LDFLAGS=""
>   
> +wasm64_memory64=1
> +
>   # Default value for a variable defining feature "foo".
>   #  * foo="no"  feature will only be used if --enable-foo arg is given
>   #  * foo=""    feature will be searched for, and if found, will be used
> @@ -239,6 +241,8 @@ for opt do
>     ;;
>     --without-default-features) default_feature="no"
>     ;;
> +  --wasm64-memory64=*) wasm64_memory64="$optarg"
> +  ;;
>     esac
>   done
>   
> @@ -537,7 +541,7 @@ case "$cpu" in
>       CPU_CFLAGS="-m32"
>       ;;
>     wasm64)
> -    CPU_CFLAGS="-m64 -sMEMORY64=1"
> +    CPU_CFLAGS="-m64 -sMEMORY64=$wasm64_memory64"
>       ;;
>   esac
>   
> @@ -795,6 +799,8 @@ for opt do
>     ;;
>     --disable-rust) rust=disabled
>     ;;
> +  --wasm64-memory64=*)
> +  ;;
>     # everything else has the same name in configure and meson
>     --*) meson_option_parse "$opt" "$optarg"
>     ;;
> @@ -920,6 +926,8 @@ Advanced options (experts only):
>     --disable-containers     don't use containers for cross-building
>     --container-engine=TYPE  which container engine to use [$container_engine]
>     --gdb=GDB-path           gdb to use for gdbstub tests [$gdb_bin]
> +  --wasm64-memory64        Used only for wasm64 build. Set -sMEMORY64 of
> +                           Emscripten to 1(default) or 2 (choices: 1/2)

I wouldn't expose "1" or "2" to the users. Instead, keep 1 as internal
default, and provide the --wasm64-32bit-address-limit option which sets
internal value to 2. Configure help could be:

    --wasm64-32bit-address-limit    Restrict wasm64 address space to
                                    32-bit (default is to use the whole
                                    64-bit range).

WDYT?
Re: [PATCH 2/4] configure: Enable to propagate -sMEMORY64 flag to Emscripten
Posted by Kohei Tokunaga 4 months, 1 week ago 
Hi Philippe,

Thanks for the suggestion.

> On 4/8/25 14:57, Kohei Tokunaga wrote:
> > Currently there are some engines that don't support wasm64 (e.g.
unsupported
> > on Safari[1]). To mitigate this issue, the configure script allows the
user
> > to use Emscripten's compatibility feature, "-sMEMORY64=2" flag[2].
> >
> > Emscripten's "-sMEMORY64=2" flag still enables 64bit pointers in C
code. But
> > this flag lowers the output binary into wasm32, with limiting the
maximum
> > memory size to 4GB. So QEMU can run on wasm32 engines.
> >
> > This commit adds "--wasm64-memory64" flag to the configure script. This
> > takes the value to propagate to Emscripten's -sMEMORY64. 1(default)
targets
> > wasm64 engines and 2 targets wasm32 engines with still enabling 64bit
> > pointers.
> >
> > [1] https://webassembly.org/features/
> > [2]
https://emscripten.org/docs/tools_reference/settings_reference.html#memory64
> >
> > Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
> > ---
> >   configure | 10 +++++++++-
> >   1 file changed, 9 insertions(+), 1 deletion(-)
> >
> > diff --git a/configure b/configure
> > index 7f3893a42f..8573f84e26 100755
> > --- a/configure
> > +++ b/configure
> > @@ -182,6 +182,8 @@ EXTRA_CXXFLAGS=""
> >   EXTRA_OBJCFLAGS=""
> >   EXTRA_LDFLAGS=""
> >
> > +wasm64_memory64=1
> > +
> >   # Default value for a variable defining feature "foo".
> >   #  * foo="no"  feature will only be used if --enable-foo arg is given
> >   #  * foo=""    feature will be searched for, and if found, will be
used
> > @@ -239,6 +241,8 @@ for opt do
> >     ;;
> >     --without-default-features) default_feature="no"
> >     ;;
> > +  --wasm64-memory64=*) wasm64_memory64="$optarg"
> > +  ;;
> >     esac
> >   done
> >
> > @@ -537,7 +541,7 @@ case "$cpu" in
> >       CPU_CFLAGS="-m32"
> >       ;;
> >     wasm64)
> > -    CPU_CFLAGS="-m64 -sMEMORY64=1"
> > +    CPU_CFLAGS="-m64 -sMEMORY64=$wasm64_memory64"
> >       ;;
> >   esac
> >
> > @@ -795,6 +799,8 @@ for opt do
> >     ;;
> >     --disable-rust) rust=disabled
> >     ;;
> > +  --wasm64-memory64=*)
> > +  ;;
> >     # everything else has the same name in configure and meson
> >     --*) meson_option_parse "$opt" "$optarg"
> >     ;;
> > @@ -920,6 +926,8 @@ Advanced options (experts only):
> >     --disable-containers     don't use containers for cross-building
> >     --container-engine=TYPE  which container engine to use
[$container_engine]
> >     --gdb=GDB-path           gdb to use for gdbstub tests [$gdb_bin]
> > +  --wasm64-memory64        Used only for wasm64 build. Set -sMEMORY64
of
> > +                           Emscripten to 1(default) or 2 (choices: 1/2)
>
> I wouldn't expose "1" or "2" to the users. Instead, keep 1 as internal
> default, and provide the --wasm64-32bit-address-limit option which sets
> internal value to 2. Configure help could be:
>
>     --wasm64-32bit-address-limit    Restrict wasm64 address space to
>                                     32-bit (default is to use the whole
>                                     64-bit range).
>
> WDYT?

It looks good to me. I'll update the patch.

Regards,
Kohei
Re: [PATCH 2/4] configure: Enable to propagate -sMEMORY64 flag to Emscripten
Posted by Pierrick Bouvier 4 months, 1 week ago 
On 8/4/25 5:57 AM, Kohei Tokunaga wrote:
> Currently there are some engines that don't support wasm64 (e.g. unsupported
> on Safari[1]). To mitigate this issue, the configure script allows the user
> to use Emscripten's compatibility feature, "-sMEMORY64=2" flag[2].
> 
> Emscripten's "-sMEMORY64=2" flag still enables 64bit pointers in C code. But
> this flag lowers the output binary into wasm32, with limiting the maximum
> memory size to 4GB. So QEMU can run on wasm32 engines.
> 
> This commit adds "--wasm64-memory64" flag to the configure script. This
> takes the value to propagate to Emscripten's -sMEMORY64. 1(default) targets
> wasm64 engines and 2 targets wasm32 engines with still enabling 64bit
> pointers.
> 
> [1] https://webassembly.org/features/
> [2] https://emscripten.org/docs/tools_reference/settings_reference.html#memory64
> 
> Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
> ---
>   configure | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)

It could be worth adding the link to documentation in commit description 
directly in configure also.
As well, the --wasm64-memory64 option help could explain that in a few 
words.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Re: [PATCH 2/4] configure: Enable to propagate -sMEMORY64 flag to Emscripten
Posted by Kohei Tokunaga 4 months, 1 week ago 
Hi Pierrick, thanks for the feedback.

> It could be worth adding the link to documentation in commit description
> directly in configure also.
> As well, the --wasm64-memory64 option help could explain that in a few
> words.

I'll add the explanation in the configure script in the next version of this
patch series.

Regards,
Kohei

Patchew 2.1-devel-b67e4c2

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