YJIT: Discard local var type info on routine call

Routines that are called from YJIT's output code can call methods, and
calling methods mean they can capture and change the environment of the
calling frame.

Discard type info whenever we perform routine calls. This is more
conservative than strictly necessary as some routines need to perform GC
allocation but can never call methods and so should never be able to
change local variables. However, manually analyzing C functions for
whether they have code paths that call methods is error prone and can go
out of date as changes land in the codebase.

Closes: shopify/yjit#300

1 files changed, 4 insertions, 0 deletions

diff --git a/yjit_codegen.c b/yjit_codegen.c
index aa352dac70..25fcfca083 100644
--- a/yjit_codegen.c
+++ b/yjit_codegen.c
@@ -184,6 +184,10 @@ jit_prepare_routine_call(jitstate_t *jit, ctx_t *ctx, x86opnd_t scratch_reg)
     jit->record_boundary_patch_point = true;
     jit_save_pc(jit, scratch_reg);
     jit_save_sp(jit, ctx);
+
+    // In case the routine calls Ruby methods, it can set local variables
+    // through Kernel#binding and other means.
+    ctx_clear_local_types(ctx);
 }
 
 // Record the current codeblock write position for rewriting into a jump into