From 6c7813a05f8772489a8543e10654d40558219baf Mon Sep 17 00:00:00 2001
From: Andy Wingo <wingo@igalia.com>
Date: Thu, 30 Jul 2020 11:51:56 +0200
Subject: [PATCH] Ensure tail caller and callee in jmpi test have compatible
 ABI

* tests/jmpi.c: Emit the tail callee using the JIT, to ensure that it
  saves and restores registers in the same way as the caller.  Fixes
  #16.
---
 tests/jmpi.c | 32 ++++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/tests/jmpi.c b/tests/jmpi.c
index 2f9213fec..e73ace055 100644
--- a/tests/jmpi.c
+++ b/tests/jmpi.c
@@ -1,21 +1,41 @@
 #include "test.h"
 
-static int tail(void) { return 42; }
+void *tail;
+
+static void *target;
 
 static void
 run_test(jit_state_t *j, uint8_t *arena_base, size_t arena_size)
 {
   jit_begin(j, arena_base, arena_size);
-
-  jit_jmpi(j, tail);
-
+  jit_enter_jit_abi(j, 0, 0, 0);
+  jit_movi(j, JIT_R0, 42);
+  jit_jmpi(j, target);
+  // Unreachable.
+  jit_breakpoint(j);
   int (*f)(void) = jit_end(j, NULL);
-
   ASSERT(f() == 42);
 }
 
+// Make the tail-call target via a separate main_helper because probably the new
+// arena will be allocated farther away, forcing nonlocal jumps.
+static void
+make_target(jit_state_t *j, uint8_t *arena_base, size_t arena_size)
+{
+  jit_begin(j, arena_base, arena_size);
+  size_t align = jit_enter_jit_abi(j, 0, 0, 0);
+  // Tail call target assumes tail caller called enter_jit_abi with compatible
+  // parameters.
+  target = jit_address(j);
+  jit_leave_jit_abi(j, 0, 0, align);
+  jit_retr(j, JIT_R0);
+  jit_end(j, NULL);
+
+  main_helper(0, NULL, run_test);
+}
+
 int
 main (int argc, char *argv[])
 {
-  return main_helper(argc, argv, run_test);
+  return main_helper(argc, argv, make_target);
 }