wasm64 target enables 64bit pointers using Emscripten's -sMEMORY64=1
flag[1]. This enables QEMU to run 64bit guests.

Although the configure script uses "uname -m" as the fallback value when
"cpu" is empty, this can't be used for Emscripten which targets to Wasm.
So, in wasm build, this commit fixes configure to require --cpu flag to be
explicitly specified by the user.

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

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
---
 configure   | 6 +++++-
 meson.build | 4 ++--
 2 files changed, 7 insertions(+), 3 deletions(-)

V3:
- This commit is under review in another patch series so please ignore it
  here.

diff --git a/configure b/configure
index 274a778764..112e4725fc 100755
--- a/configure
+++ b/configure
@@ -365,7 +365,6 @@ elif check_define __APPLE__; then
   host_os=darwin
 elif check_define EMSCRIPTEN ; then
   host_os=emscripten
-  cpu=wasm32
   cross_compile="yes"
 else
   # This is a fatal error, but don't report it yet, because we
@@ -425,6 +424,8 @@ elif check_define __aarch64__ ; then
   cpu="aarch64"
 elif check_define __loongarch64 ; then
   cpu="loongarch64"
+elif check_define EMSCRIPTEN ; then
+  error_exit "wasm32 or wasm64 must be specified to the cpu flag"
 else
   # Using uname is really broken, but it is just a fallback for architectures
   # that are going to use TCI anyway
@@ -535,6 +536,9 @@ case "$cpu" in
   wasm32)
     CPU_CFLAGS="-m32"
     ;;
+  wasm64)
+    CPU_CFLAGS="-m64 -sMEMORY64=1"
+    ;;
 esac
 
 if test -n "$host_arch" && {
diff --git a/meson.build b/meson.build
index 50c774a195..44bb7ed334 100644
--- a/meson.build
+++ b/meson.build
@@ -52,7 +52,7 @@ qapi_trace_events = []
 bsd_oses = ['gnu/kfreebsd', 'freebsd', 'netbsd', 'openbsd', 'dragonfly', 'darwin']
 supported_oses = ['windows', 'freebsd', 'netbsd', 'openbsd', 'darwin', 'sunos', 'linux', 'emscripten']
 supported_cpus = ['ppc', 'ppc64', 's390x', 'riscv32', 'riscv64', 'x86', 'x86_64',
-  'arm', 'aarch64', 'loongarch64', 'mips', 'mips64', 'sparc64', 'wasm32']
+  'arm', 'aarch64', 'loongarch64', 'mips', 'mips64', 'sparc64', 'wasm32', 'wasm64']
 
 cpu = host_machine.cpu_family()
 
@@ -916,7 +916,7 @@ if have_tcg
     if not get_option('tcg_interpreter')
       error('Unsupported CPU @0@, try --enable-tcg-interpreter'.format(cpu))
     endif
-  elif host_arch == 'wasm32'
+  elif host_arch == 'wasm32' or host_arch == 'wasm64'
     if not get_option('tcg_interpreter')
       error('WebAssembly host requires --enable-tcg-interpreter')
     endif
-- 
2.43.0