From 678369f187c0dc3cf8ed3dbe95048494356f518a Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Fri, 13 May 2016 11:15:23 -0600
Subject: [PATCH] avoid generating shared call code for too many arguments

Although the JIT would not try to use a block of shared code for more
than a certain number of arguments, it could in rare cases (related to
self tail calls, for example) generate the code and attempt to install
it in the array of shared-code pointers.
---
 racket/src/racket/src/jitcall.c | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/racket/src/racket/src/jitcall.c b/racket/src/racket/src/jitcall.c
index 39d0c90fc6..7d01aa6f63 100644
--- a/racket/src/racket/src/jitcall.c
+++ b/racket/src/racket/src/jitcall.c
@@ -2252,12 +2252,17 @@ int scheme_generate_app(Scheme_App_Rec *app, Scheme_Object **alt_rands, int num_
     /* if unboxed_non_tail_args, then we'll also use index 4 in place of dp */
 
     if (is_tail) {
-      if (!sjc.shared_tail_code[dp][num_rands]) {
-	code = scheme_generate_shared_call(num_rands, jitter, multi_ok, result_ignored, is_tail, 
-                                           direct_prim, direct_native, 0, 0);
-	sjc.shared_tail_code[dp][num_rands] = code;
+      if (num_rands < MAX_SHARED_CALL_RANDS) {
+        if (!sjc.shared_tail_code[dp][num_rands]) {
+          code = scheme_generate_shared_call(num_rands, jitter, multi_ok, result_ignored, is_tail, 
+                                             direct_prim, direct_native, 0, 0);
+          sjc.shared_tail_code[dp][num_rands] = code;
+        }
+        code = sjc.shared_tail_code[dp][num_rands];
+      } else {
+        /* We won't use this code pointer, because `direct_self` or similar. */
+        code = NULL;
       }
-      code = sjc.shared_tail_code[dp][num_rands];
       CHECK_NESTED_GENERATE();
       if (direct_self) {
         LOG_IT(("<-self\n"));
@@ -2329,14 +2334,19 @@ int scheme_generate_app(Scheme_App_Rec *app, Scheme_Object **alt_rands, int num_
         unboxed_code = NULL;
 #endif
 
-      if (!sjc.shared_non_tail_code[dp][num_rands][mo]) {
-        scheme_ensure_retry_available(jitter, multi_ok, result_ignored);
-	code = scheme_generate_shared_call(num_rands, jitter, multi_ok, result_ignored, is_tail, 
-                                           direct_prim, direct_native, nontail_self, 0);
-	sjc.shared_non_tail_code[dp][num_rands][mo] = code;
+      if (num_rands < MAX_SHARED_CALL_RANDS) {
+        if (!sjc.shared_non_tail_code[dp][num_rands][mo]) {
+          scheme_ensure_retry_available(jitter, multi_ok, result_ignored);
+          code = scheme_generate_shared_call(num_rands, jitter, multi_ok, result_ignored, is_tail, 
+                                             direct_prim, direct_native, nontail_self, 0);
+          sjc.shared_non_tail_code[dp][num_rands][mo] = code;
+        }
+        code = sjc.shared_non_tail_code[dp][num_rands][mo];
+      } else {
+        /* Not used, due to `apply_to_list` */
+        code = NULL;
       }
       LOG_IT(("<-non-tail %d %d %d\n", dp, num_rands, mo));
-      code = sjc.shared_non_tail_code[dp][num_rands][mo];
       CHECK_NESTED_GENERATE();
 
       if (nontail_self) {