ZJIT: Load Ruby params in bb0 instead of entry point

Previously, we stored the params at the wrong spots on the stack because after
gen_entry_params() we touched the SP in gen_function() for bb0 in
asm.frame_setup() and in the explicit stack pointer bump. Later, when we
read off of SP using the same offset we don't load what we stored
because SP has moved. (This is like the _iterator invalidation
problem_.)

Load the params in bb0 after all the SP movements.

Author: XrXr

zjit/src/codegen.rs

@@ -113,7 +113,7 @@ fn gen_iseq_entry_point(iseq: IseqPtr) -> *const u8 {
             payload.start_ptr = Some(start_ptr);
 
             // Compile an entry point to the JIT code
-            (gen_entry(cb, iseq, &function, start_ptr), branch_iseqs)
+            (gen_entry(cb, iseq, start_ptr), branch_iseqs)
         },
         None => (None, vec![]),
     };
@@ -144,11 +144,10 @@ fn gen_iseq_entry_point(iseq: IseqPtr) -> *const u8 {
 }
 
 /// Compile a JIT entry
-fn gen_entry(cb: &mut CodeBlock, iseq: IseqPtr, function: &Function, function_ptr: CodePtr) -> Option<CodePtr> {
+fn gen_entry(cb: &mut CodeBlock, iseq: IseqPtr, function_ptr: CodePtr) -> Option<CodePtr> {
     // Set up registers for CFP, EC, SP, and basic block arguments
     let mut asm = Assembler::new();
     gen_entry_prologue(&mut asm, iseq);
-    gen_entry_params(&mut asm, iseq, function.block(BlockId(0)));
 
     // Jump to the first block using a call instruction
     asm.ccall(function_ptr.raw_ptr(cb) as *const u8, vec![]);
@@ -216,6 +215,8 @@ fn gen_function(cb: &mut CodeBlock, iseq: IseqPtr, function: &Function) -> Optio
                 let new_sp = asm.sub(NATIVE_STACK_PTR, jit.c_stack_bytes.into());
                 asm.mov(NATIVE_STACK_PTR, new_sp);
             }
+
+            gen_entry_params(&mut asm, iseq, function.block(BlockId(0)));
         }
 
         // Compile all parameters