YJIT: Fix unexpected truncation when outputing VALUE

Previously, YJIT incorrectly discarded the upper 32 bits of the object
pointer when writing out VALUEs to setup default keyword arguments.

In addition to incorrectly truncating, the output pointers were not
properly tracked for handling GC compaction moving the referenced
objects.

YJIT previously attempted to encode a mov instruction with a memory
destination and a 64 bit immediate when there is no such encoding
possible in the ISA. Add an assert to mitigate not being able to
catch this at build time.

1 files changed, 4 insertions, 2 deletions

diff --git a/yjit_codegen.c b/yjit_codegen.c
index 3378f1500d..38b830a097 100644
--- a/yjit_codegen.c
+++ b/yjit_codegen.c
@@ -3698,7 +3698,7 @@ gen_send_iseq(jitstate_t *jit, ctx_t *ctx, const struct rb_callinfo *ci, const r
 
         // This struct represents the metadata about the callee-specified
         // keyword parameters.
-        const struct rb_iseq_param_keyword *keyword = iseq->body->param.keyword;
+        const struct rb_iseq_param_keyword *const keyword = iseq->body->param.keyword;
 
         ADD_COMMENT(cb, "keyword args");
 
@@ -3748,7 +3748,9 @@ gen_send_iseq(jitstate_t *jit, ctx_t *ctx, const struct rb_callinfo *ci, const r
                     default_value = Qnil;
                 }
 
-                mov(cb, default_arg, imm_opnd(default_value));
+                // GC might move default_value.
+                jit_mov_gc_ptr(jit, cb, REG0, default_value);
+                mov(cb, default_arg, REG0);
 
                 caller_kwargs[kwarg_idx++] = callee_kwarg;
             }