add a flag to indicate which slots are accessed

src/ast.scm

@@ -434,7 +434,7 @@
 (define (vinfo:capt v) (< 0 (logand (caddr v) 1)))
 (define (vinfo:asgn v) (< 0 (logand (caddr v) 2)))
 (define (vinfo:never-undef v) (< 0 (logand (caddr v) 4)))
-(define (vinfo:const v) (< 0 (logand (caddr v) 8)))
+(define (vinfo:read v) (< 0 (logand (caddr v) 8)))
 (define (vinfo:sa v) (< 0 (logand (caddr v) 16)))
 (define (set-bit x b val) (if val (logior x b) (logand x (lognot b))))
 ;; record whether var is captured
@@ -443,8 +443,8 @@
 (define (vinfo:set-asgn! v a)  (set-car! (cddr v) (set-bit (caddr v) 2 a)))
 ;; whether the assignments to var are known to dominate its usages
 (define (vinfo:set-never-undef! v a) (set-car! (cddr v) (set-bit (caddr v) 4 a)))
-;; whether var is const
-(define (vinfo:set-const! v a) (set-car! (cddr v) (set-bit (caddr v) 8 a)))
+;; whether var is ever read
+(define (vinfo:set-read! v a) (set-car! (cddr v) (set-bit (caddr v) 8 a)))
 ;; whether var is assigned once
 (define (vinfo:set-sa! v a)    (set-car! (cddr v) (set-bit (caddr v) 16 a)))
 ;; occurs undef: mask 32

src/julia-syntax.scm

@@ -2641,7 +2641,12 @@
 ;; where var-info-lst is a list of var-info records
 (define (analyze-vars e env captvars sp)
   (if (or (atom? e) (quoted? e))
-      e
+      (begin
+        (if (symbol? e)
+            (let ((vi (var-info-for e env)))
+              (if vi
+                  (vinfo:set-read! vi #t))))
+        e)
       (case (car e)
         ((local-def) ;; a local that we know has an assignment that dominates all usages
          (let ((vi (var-info-for (cadr e) env)))

src/method.c

@@ -259,7 +259,7 @@ static void jl_code_info_set_ast(jl_code_info_t *li, jl_expr_t *ast)
     li->ssaflags = jl_alloc_array_1d(jl_array_uint8_type, 0);
 
     // Flags that need to be copied to slotflags
-    const uint8_t vinfo_mask = 16 | 32 | 64;
+    const uint8_t vinfo_mask = 8 | 16 | 32 | 64;
     int i;
     for (i = 0; i < nslots; i++) {
         jl_value_t *vi = jl_array_ptr_ref(vis, i);