From 2e707ee66f484c11d4548011911ad17bec2063b9 Mon Sep 17 00:00:00 2001
From: John Hawthorn <john@hawthorn.email>
Date: Tue, 3 Aug 2021 10:31:26 -0700
Subject: Don't generate entry point when PC != 0

If we hit this at PC > 0 (ie. with an optional argument) the provided
types and context are likely incorrect and it is likely this block can't
be used.
---
 yjit_core.c | 6 ++++++
 1 file changed, 6 insertions(+)

(limited to 'yjit_core.c')

diff --git a/yjit_core.c b/yjit_core.c
index 45386dea23..95bdcc1fa4 100644
--- a/yjit_core.c
+++ b/yjit_core.c
@@ -613,6 +613,12 @@ block_t* gen_block_version(blockid_t blockid, const ctx_t* start_ctx, rb_executi
 // Generate a block version that is an entry point inserted into an iseq
 uint8_t* gen_entry_point(const rb_iseq_t *iseq, uint32_t insn_idx, rb_execution_context_t *ec)
 {
+    // If we aren't at PC 0, don't generate code
+    // See yjit_pc_guard
+    if (iseq->body->iseq_encoded != ec->cfp->pc) {
+        return NULL;
+    }
+
     // The entry context makes no assumptions about types
     blockid_t blockid = { iseq, insn_idx };
 
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