1 files changed, 83 insertions, 0 deletions
diff --git a/libc-top-half/musl/src/setjmp/wasm32/rt.c b/libc-top-half/musl/src/setjmp/wasm32/rt.c
new file mode 100644
index 0000000..24e4e33
--- /dev/null
+++ b/libc-top-half/musl/src/setjmp/wasm32/rt.c
@@ -0,0 +1,83 @@
+/*
+ * a runtime implementation for
+ * https://github.com/llvm/llvm-project/pull/84137
+ * https://docs.google.com/document/d/1ZvTPT36K5jjiedF8MCXbEmYjULJjI723aOAks1IdLLg/edit
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+
+/*
+ * function prototypes
+ */
+void __wasm_setjmp(void *env, uint32_t label, void *func_invocation_id);
+uint32_t __wasm_setjmp_test(void *env, void *func_invocation_id);
+void __wasm_longjmp(void *env, int val);
+
+/*
+ * jmp_buf should have large enough size and alignment to contain
+ * this structure.
+ */
+struct jmp_buf_impl {
+        void *func_invocation_id;
+        uint32_t label;
+
+        /*
+         * this is a temorary storage used by the communication between
+         * __wasm_sjlj_longjmp and WebAssemblyLowerEmscriptenEHSjL-generated
+         * logic.
+         * ideally, this can be replaced with multivalue.
+         */
+        struct arg {
+                void *env;
+                int val;
+        } arg;
+};
+
+void
+__wasm_setjmp(void *env, uint32_t label, void *func_invocation_id)
+{
+        struct jmp_buf_impl *jb = env;
+        if (label == 0) { /* ABI contract */
+                __builtin_trap();
+        }
+        if (func_invocation_id == NULL) { /* sanity check */
+                __builtin_trap();
+        }
+        jb->func_invocation_id = func_invocation_id;
+        jb->label = label;
+}
+
+uint32_t
+__wasm_setjmp_test(void *env, void *func_invocation_id)
+{
+        struct jmp_buf_impl *jb = env;
+        if (jb->label == 0) { /* ABI contract */
+                __builtin_trap();
+        }
+        if (func_invocation_id == NULL) { /* sanity check */
+                __builtin_trap();
+        }
+        if (jb->func_invocation_id == func_invocation_id) {
+                return jb->label;
+        }
+        return 0;
+}
+
+void
+__wasm_longjmp(void *env, int val)
+{
+        struct jmp_buf_impl *jb = env;
+        struct arg *arg = &jb->arg;
+        /*
+         * C standard says:
+         * The longjmp function cannot cause the setjmp macro to return
+         * the value 0; if val is 0, the setjmp macro returns the value 1.
+         */
+        if (val == 0) {
+                val = 1;
+        }
+        arg->env = env;
+        arg->val = val;
+        __builtin_wasm_throw(1, arg); /* 1 == C_LONGJMP */
+}