[wasm] add asyncify based setjmp, fiber, register scan emulation

configure.ac: setup build tools and register objects

main.c: wrap main with rb_wasm_rt_start to handle asyncify unwinds

tool/m4/ruby_wasm_tools.m4: setup default command based on WASI_SDK_PATH
environment variable. checks wasm-opt which is used for asyncify.

tool/wasm-clangw wasm/wasm-opt: a clang wrapper which replaces real
wasm-opt with do-nothing wasm-opt to avoid misoptimization before
asyncify. asyncify is performed at POSTLINK, but clang linker driver
tries to run optimization by wasm-opt unconditionally. inlining pass
at wasm level breaks asyncify's assumption, so should not optimize
before POSTLIK.

wasm/GNUmakefile.in: wasm specific rules to compile objects

1 files changed, 9 insertions, 0 deletions

diff --git a/tool/wasm-clangw b/tool/wasm-clangw
new file mode 100755
index 0000000000..9ebdfda75a
--- /dev/null
+++ b/tool/wasm-clangw
@@ -0,0 +1,9 @@
+#!/bin/sh
+# A Clang wrapper script to fake the clang linker driver.
+# Clang linker automatically uses wasm-opt with -O if it found.
+# However optimization before asyncify causes misoptimization,
+# so wrap clang to insert our fake wasm-opt, which does nothing, in PATH.
+
+src_dir="$(cd "$(dirname "$0")/../wasm" && pwd)"
+export PATH="$src_dir:$PATH"
+exec "$@"