Revert exception threshold logic. Document option in yjid.md

doc/yjit/yjit.md

@@ -165,9 +165,11 @@ YJIT supports all command-line options supported by upstream CRuby, but also add
 
 - `--yjit`: enable YJIT (disabled by default)
 - `--yjit-call-threshold=N`: number of calls after which YJIT begins to compile a function (default 30)
+- `--yjit-cold-threshold=N`: number of calls after which an ISEQ is considered cold and not
+compiled, lower values mean less code is compiled (default 200000)
 - `--yjit-exec-mem-size=N`: size of the executable memory block to allocate, in MiB (default 64 MiB in Ruby 3.2, 128 MiB in Ruby 3.3+)
 - `--yjit-stats`: print statistics after the execution of a program (incurs a run-time cost)
-- `--yjit-stats=quiet`: gather statistics while running a program but don't print them. Stats are accessible through `RubyVM::YJIT.runtime_stats`. (incurs a run-time cost) 
+- `--yjit-stats=quiet`: gather statistics while running a program but don't print them. Stats are accessible through `RubyVM::YJIT.runtime_stats`. (incurs a run-time cost)
 - `--yjit-trace-exits`: produce a Marshal dump of backtraces from specific exits. Automatically enables `--yjit-stats` (must configure and build with `--enable-yjit=stats` to use this)
 - `--yjit-max-versions=N`: maximum number of versions to generate per basic block (default 4)
 - `--yjit-greedy-versioning`: greedy versioning mode (disabled by default, may increase code size)

vm.c

@@ -442,7 +442,7 @@ jit_compile_exception(rb_execution_context_t *ec)
     // Increment the ISEQ's call counter and trigger JIT compilation if not compiled
     if (body->jit_exception == NULL) {
         body->jit_exception_calls++;
-        if (rb_yjit_threshold_hit(iseq, body->jit_exception_calls)) {
+        if (body->jit_exception_calls == rb_yjit_call_threshold()) {
             rb_yjit_compile_iseq(iseq, ec, true);
         }
     }

yjit.h

@@ -27,6 +27,7 @@
 // Expose these as declarations since we are building YJIT.
 bool rb_yjit_enabled_p(void);
 bool rb_yjit_compile_new_iseqs(void);
+unsigned long rb_yjit_call_threshold();
 bool rb_yjit_threshold_hit(const rb_iseq_t *const iseq, unsigned long total_calls);
 void rb_yjit_invalidate_all_method_lookup_assumptions(void);
 void rb_yjit_cme_invalidate(rb_callable_method_entry_t *cme);
@@ -49,6 +50,7 @@ void rb_yjit_tracing_invalidate_all(void);
 
 static inline bool rb_yjit_enabled_p(void) { return false; }
 static inline bool rb_yjit_compile_new_iseqs(void) { return false; }
+static inline unsigned long rb_yjit_call_threshold() { return 0; }
 static inline bool rb_yjit_threshold_hit(const rb_iseq_t *const iseq, unsigned long total_calls) { return false; }
 static inline void rb_yjit_invalidate_all_method_lookup_assumptions(void) {}
 static inline void rb_yjit_cme_invalidate(rb_callable_method_entry_t *cme) {}

yjit/src/yjit.rs

@@ -46,6 +46,12 @@ pub fn yjit_enabled_p() -> bool {
     YJIT_ENABLED.load(Ordering::Acquire)
 }
 
+/// Make the call threshold available to C
+#[no_mangle]
+pub extern "C" fn rb_yjit_call_threshold() -> raw::c_ulong {
+    get_option!(call_threshold) as raw::c_ulong
+}
+
 // Counter to serve as a proxy for execution time, total number of calls
 static mut TOTAL_ENTRY_HITS: u64 = 0;