YJIT: Support splat with C methods with -1 arity

Usually we deal with splats by speculating that they're of a specific
size. In this case, the C method takes a pointer and a length, so
we can support changing sizes just fine.

1 files changed, 45 insertions, 0 deletions

diff --git a/yjit.c b/yjit.c
index 207974073b..8632361699 100644
--- a/yjit.c
+++ b/yjit.c
@@ -890,6 +890,51 @@ rb_yjit_ruby2_keywords_splat_p(VALUE obj)
     return FL_TEST_RAW(last, RHASH_PASS_AS_KEYWORDS);
 }
 
+// Checks to establish preconditions for rb_yjit_splat_varg_cfunc()
+VALUE
+rb_yjit_splat_varg_checks(VALUE *sp, VALUE splat_array, rb_control_frame_t *cfp)
+{
+    // We inserted a T_ARRAY guard before this call
+    long len = RARRAY_LEN(splat_array);
+
+    // Large splat arrays need a separate allocation
+    if (len < 0 || len > VM_ARGC_STACK_MAX) return Qfalse;
+
+    // Would we overflow if we put the contents of the array onto the stack?
+    if (sp + len > (VALUE *)(cfp - 2)) return Qfalse;
+
+    return Qtrue;
+}
+
+// Push array elements to the stack for a C method that has a variable number
+// of parameters. Returns the number of arguments the splat array contributes.
+int
+rb_yjit_splat_varg_cfunc(VALUE *stack_splat_array, bool sole_splat)
+{
+    VALUE splat_array = *stack_splat_array;
+    int len;
+
+    // We already checked that length fits in `int`
+    RUBY_ASSERT(RB_TYPE_P(splat_array, T_ARRAY));
+    len = (int)RARRAY_LEN(splat_array);
+
+    // If this is a splat call without any keyword arguments, exclude the
+    // ruby2_keywords hash if it's empty
+    if (sole_splat && len > 0) {
+        VALUE last_hash = RARRAY_AREF(splat_array, len - 1);
+        if (RB_TYPE_P(last_hash, T_HASH) &&
+                FL_TEST_RAW(last_hash, RHASH_PASS_AS_KEYWORDS) &&
+                RHASH_EMPTY_P(last_hash)) {
+            len--;
+        }
+    }
+
+    // Push the contents of the array onto the stack
+    MEMCPY(stack_splat_array, RARRAY_CONST_PTR(splat_array), VALUE, len);
+
+    return len;
+}
+
 // Print the Ruby source location of some ISEQ for debugging purposes
 void
 rb_yjit_dump_iseq_loc(const rb_iseq_t *iseq, uint32_t insn_idx)