unwinder: fix 'isDeopt' check

We used to not detect deopt frames in release mode this was because we are looking for 'astInterpretDeopt'
in the call stack but this did not work because the compiler optimized this function to a jmp to astInterpretDeoptInner.

I tested different compiler attributes but I ended up implementing this small wrapper function in assembler
because I think it's the most reliable way to make sure it does appear in the call stack.

src/codegen/ast_interpreter.cpp

@@ -1857,10 +1857,11 @@ Box* astInterpretFunctionEval(FunctionMetadata* md, Box* globals, Box* boxedLoca
     return v ? v : None;
 }
 
-static Box* astInterpretDeoptInner(FunctionMetadata* md, AST_expr* after_expr, AST_stmt* enclosing_stmt, Box* expr_val,
-                                   FrameStackState frame_state) __attribute__((noinline));
-static Box* astInterpretDeoptInner(FunctionMetadata* md, AST_expr* after_expr, AST_stmt* enclosing_stmt, Box* expr_val,
-                                   FrameStackState frame_state) {
+// caution when changing the function arguments: this function gets called from an assembler wrapper!
+extern "C" Box* astInterpretDeoptFromASM(FunctionMetadata* md, AST_expr* after_expr, AST_stmt* enclosing_stmt,
+                                         Box* expr_val, FrameStackState frame_state) {
+    static_assert(sizeof(FrameStackState) <= 2 * 8, "astInterpretDeopt assumes that all args get passed in regs!");
+
     assert(md);
     assert(enclosing_stmt);
     assert(frame_state.locals);
@@ -1958,11 +1959,6 @@ static Box* astInterpretDeoptInner(FunctionMetadata* md, AST_expr* after_expr, A
     return v ? v : None;
 }
 
-Box* astInterpretDeopt(FunctionMetadata* md, AST_expr* after_expr, AST_stmt* enclosing_stmt, Box* expr_val,
-                       FrameStackState frame_state) {
-    return astInterpretDeoptInner(md, after_expr, enclosing_stmt, expr_val, frame_state);
-}
-
 extern "C" void printExprHelper(Box* obj) {
     Box* displayhook = PySys_GetObject("displayhook");
     if (!displayhook)

src/codegen/ast_interpreter.h

@@ -77,8 +77,9 @@ struct Value {
 Box* astInterpretFunction(FunctionMetadata* f, Box* closure, Box* generator, Box* globals, Box* arg1, Box* arg2,
                           Box* arg3, Box** args);
 Box* astInterpretFunctionEval(FunctionMetadata* cf, Box* globals, Box* boxedLocals);
-Box* astInterpretDeopt(FunctionMetadata* cf, AST_expr* after_expr, AST_stmt* enclosing_stmt, Box* expr_val,
-                       FrameStackState frame_state);
+// this function is implemented in the src/codegen/ast_interpreter_exec.S assembler file
+extern "C" Box* astInterpretDeopt(FunctionMetadata* cf, AST_expr* after_expr, AST_stmt* enclosing_stmt, Box* expr_val,
+                                  FrameStackState frame_state);
 
 struct FrameInfo;
 FrameInfo* getFrameInfoForInterpretedFrame(void* frame_ptr);

src/codegen/ast_interpreter_exec.S

@@ -32,11 +32,36 @@ executeInnerAndSetupFrame:
     sub $16, %rsp
     mov %rdi, -8(%rbp)
     call executeInnerFromASM
-    leave
+    add $16, %rsp
+    pop %rbp
     .cfi_def_cfa            rsp,8
     ret
     .cfi_endproc
 .size executeInnerAndSetupFrame,.-executeInnerAndSetupFrame
 
+// This function is just a small wrapper around astInterpretDeoptFromASM.
+// Our unwinder must be able to detect deopt frames and by writting this wrapper in assembler we can be sure to correctly
+// detect the frame independent of compiler optimizations because this function will always appear in the call stack.
+//
+// Box* astInterpretDeopt(FunctionMetadata* cf, AST_expr* after_expr, AST_stmt* enclosing_stmt, Box* expr_val,
+//                        FrameStackState frame_state);
+.text
+.globl astInterpretDeopt
+.type astInterpretDeopt,@function
+.align 16
+astInterpretDeopt:
+    .cfi_startproc
+    push %rbp
+    .cfi_def_cfa_offset     16
+    .cfi_offset             rbp,-16
+    mov %rsp, %rbp
+    .cfi_def_cfa_register   rbp
+    call astInterpretDeoptFromASM
+    pop %rbp
+    .cfi_def_cfa            rsp,8
+    ret
+    .cfi_endproc
+.size astInterpretDeopt,.-astInterpretDeopt
+
 .section .note.GNU-stack,"",%progbits // we don't need executable stack