Fix closure structure so that first entry is word-aligned.

diff --git a/src/compiler/machines/svm/machine.scm b/src/compiler/machines/svm/machine.scm
index 12488c1882234aee70243f6cc125fbd6a7744ab2..10c51e873e632a845c26f6bf6a4e89ed6bbeb285 100644 (file)
--- a/src/compiler/machines/svm/machine.scm
+++ b/src/compiler/machines/svm/machine.scm
@@ -147,16 +147,16 @@ USA.
 ;; See microcode/cmpintmd/svm1.c for a description of the layout.
 
 ;; Offset of the first object in the closure from the address of the
-;; first closure entry point, in words.
+;; first closure entry point, in words.  In order to make this work,
+;; we add padding to the closure-count field so that the first entry
+;; is aligned on an object boundary.
 
 (define (closure-first-offset count entry)
   entry
   (if (= count 0)
       1
-      ;; This returns the offset in bytes, it isn't necessarily in words.
-      (receive (entries entries-size padding-size) (make-closure-entries count)
-       entries-size padding-size
-       (+ 2 (car (car entries))))))
+      (+ (integer-ceiling (* count 3) address-units-per-object)
+        count)))
 
 ;; Offset of the first object in the closure from the address of the
 ;; manifest-closure header word, in words.
@@ -164,71 +164,15 @@ USA.
 (define (closure-object-first-offset count)
   (if (= count 0)
       1
-      (receive (entries entries-size padding-size) (make-closure-entries count)
-       entries
-       (quotient (+ 2 entries-size padding-size)
-                 address-units-per-object))))
+      (+ 2 (closure-first-offset count 0))))
 
 ;; Increment from one closure entry address to another, in bytes.
 
 (define (closure-entry-distance count entry entry*)
-  (* 10 (- entry* entry)))
+  (* 3 (- entry* entry)))
 
 ;; Increment from a given closure address to the first closure
 ;; address, in bytes.  Usually negative.
 
 (define (closure-environment-adjustment count entry)
-  (closure-entry-distance count entry 0))
-
-
-;; This could get stuck toggling between two states.  It's probably
-;; not worth running the ITERATION loop more than a couple of times.
-(define (make-closure-entries count)
-  (let ((last (- count 1))
-       (initial-padding (padding-size (* count 9))))
-    (let ((entries
-          (reverse!
-           (make-initialized-list count
-             (lambda (i)
-               (cons (+ (* (- last i) 9)
-                        initial-padding
-                        (* i 4))
-                     9))))))
-      (let iteration ((padding initial-padding))
-       (let loop ((entries entries))
-         (if (pair? entries)
-             (let ((entry (car entries))
-                   (entries (cdr entries)))
-               (let ((size* (offset->entry-size (car entry)))
-                     (size (cdr entry)))
-                 (if (not (= size* size))
-                     (begin
-                       (set-cdr! entry size*)
-                       (adjust-entries! entries (- size size*)))))
-               (loop entries))))
-       (let ((entries-size (entries-size entries)))
-         (let ((padding* (padding-size entries-size)))
-           (if (not (= padding* padding))
-               (begin
-                 (adjust-entries! entries (- padding padding*))
-                 (iteration padding*))
-               (values (map car (reverse! entries))
-                       entries-size
-                       padding))))))))
-
-(define (entries-size entries)
-  (reduce + 0 (map cdr entries)))
-
-(define (padding-size entries-size)
-  (let ((entries-size (+ entries-size 2)))
-    (- (* (integer-ceiling entries-size 4) 4) entries-size)))
-
-(define (offset->entry-size offset)
-  (cond ((< offset #x100) 6)
-       ((< offset #x10000) 7)
-       (else 9)))
-
-(define (adjust-entries! entries delta)
-  (for-each (lambda (entry)
-             (set-car! entry (- (car entry) delta)))
-           entries))
\ No newline at end of file
+  (closure-entry-distance count entry 0))
\ No newline at end of file

diff --git a/src/microcode/cmpintmd/svm1.c b/src/microcode/cmpintmd/svm1.c
index 5ec801c677893ea92dc01a7b94c486574a743a9d..183370cc06b042281e25c23c75d2ea3248975758 100644 (file)
--- a/src/microcode/cmpintmd/svm1.c
+++ b/src/microcode/cmpintmd/svm1.c
@@ -224,28 +224,30 @@ write_u16 (unsigned int n, insn_t * address)
 
    For example, on a 32-bit machine with count == 3 and 4 value cells:
 
-   0x00    TC_MANIFEST_CLOSURE | n_words == 11
+   0x00    TC_MANIFEST_CLOSURE | n_words == 12
+
    0x04    count == 3
+   0x06    2 padding bytes (next address must be word-aligned)
 
-   0x06    SVM1_INST_ENTER_CLOSURE
-   0x07    index == 0
+   0x08    SVM1_INST_ENTER_CLOSURE
+   0x09    index == 0
 
-   0x09    SVM1_INST_ENTER_CLOSURE
-   0x0A    index == 1
+   0x0B    SVM1_INST_ENTER_CLOSURE
+   0x0C    index == 1
 
-   0x0C    SVM1_INST_ENTER_CLOSURE
-   0x0D    index == 2
+   0x0E    SVM1_INST_ENTER_CLOSURE
+   0x0F    index == 2
 
-   0x0F    1 padding byte
+   0x11    3 padding bytes (next address must be word-aligned)
 
-   0x10    target 0
-   0x14    target 1
-   0x18    target 2
+   0x14    target 0
+   0x18    target 1
+   0x1C    target 2
 
-   0x1C    value cell 0
-   0x20    value cell 1
-   0x24    value cell 2
-   0x28    value cell 3
+   0x20    value cell 0
+   0x24    value cell 1
+   0x28    value cell 2
+   0x2C    value cell 3
 
    */
 

diff --git a/src/microcode/cmpintmd/svm1.h b/src/microcode/cmpintmd/svm1.h
index 4ddf04cf78172a89db69495f33f9c06e83f86e93..732336c6f936f50974f4d39452fe302dedb275d8 100644 (file)
--- a/src/microcode/cmpintmd/svm1.h
+++ b/src/microcode/cmpintmd/svm1.h
@@ -46,8 +46,10 @@ typedef byte_t insn_t;
    instructions are stored.  */
 #define CC_ENTRY_GC_TRAP_SIZE 0
 
-/* Size of closure count in insn_t units.  */
-#define CLOSURE_COUNT_SIZE 2
+/* Size of closure count in insn_t units.  Only first two bytes
+   contain the count, but we must add padding to move the first entry
+   to a word boundary.  */
+#define CLOSURE_COUNT_SIZE SIZEOF_SCHEME_OBJECT
 
 /* Size of closure entry in insn_t units.  */
 #define CLOSURE_ENTRY_SIZE 3