find_replace: cover o3 function prologues on every backend

arm64, llvm and the region-interpreter rdrop path now watch the two
prologue words the way the x86-64 jit already did, so icon.replace_function's
lit+jmp patch retires a compiled callee (and clears fn_nat) instead of leaving
a stale stub. three new icon regressions: repeated o3 replace, failed
publication keeps the old entry, and a direct call after warming the region.

1 files changed, 17 insertions, 0 deletions

diff --git a/tests/icon/regression/o3_direct_replace.zc b/tests/icon/regression/o3_direct_replace.zc
new file mode 100644
index 0000000..efcd0be
--- /dev/null
+++ b/tests/icon/regression/o3_direct_replace.zc
@@ -0,0 +1,17 @@
+include rt;
+include run;
+include icon;
+// replace an o3 function and call it directly (entry via the patched prologue),
+// after warming the compiled region so the store must drop it.
+o3 int target() { return 1; }
+fn main() {
+	int i, s = 0;
+	for (i = 0; i < 100; i++) s += target();
+	rt.put_n(s); rt.put_c(' ');
+	let one = run.tokens("1"), two = run.tokens("2");
+	rt.put_n(icon.find_replace(target, one, two)); rt.put_c(' ');
+	s = 0;
+	for (i = 0; i < 100; i++) s += target();
+	rt.put_n(s); rt.put_c(10);
+	return 0;
+}