fix self tail recursion to different case-lambda clauses

http://savannah.gnu.org/bugs/?33362

* module/language/tree-il/compile-glil.scm (flatten-lambda-case): Rename
  from flatten, as it really just takes a particular case.  Instead of
  iteratively compiling lambda cases through `comp', tail-call through
  flatten-lambda-case.  This allows code to see which case it's being
  compiled in.  Take advantage of that to limit the self-tail-call
  optimization to self-calls to the same case -- otherwise we might be
  jumping to a label without having reserved the right number of
  locals.
  (flatten-lambda): Adapt the caller.

* test-suite/tests/compiler.test ("case-lambda"): Add a test.

module/language/tree-il/compile-glil.scm

@@ -207,10 +207,12 @@
          ;; write source info for proc
          (if src (emit-code #f (make-glil-source src)))
          ;; compile the body, yo
-         (flatten body allocation x self-label (car (hashq-ref allocation x))
+         (flatten-lambda-case body allocation x self-label
+                              (car (hashq-ref allocation x))
                               emit-code)))))))
 
-(define (flatten x allocation self self-label fix-labels emit-code)
+(define (flatten-lambda-case lcase allocation self self-label fix-labels
+                             emit-code)
   (define (emit-label label)
     (emit-code #f (make-glil-label label)))
   (define (emit-branch src inst label)
@@ -218,7 +220,7 @@
 
   ;; RA: "return address"; #f unless we're in a non-tail fix with labels
   ;; MVRA: "multiple-values return address"; #f unless we're in a let-values
-  (let comp ((x x) (context 'tail) (RA #f) (MVRA #f))
+  (let comp ((x lcase) (context 'tail) (RA #f) (MVRA #f))
     (define (comp-tail tree) (comp tree context RA MVRA))
     (define (comp-push tree) (comp tree 'push #f #f))
     (define (comp-drop tree) (comp tree 'drop #f #f))
@@ -422,20 +424,15 @@
                  (error "bad primitive op: too many pushes"
                         op (instruction-pushes op))))))
         
-        ;; self-call in tail position
+        ;; call to the same lambda-case in tail position
         ((and (lexical-ref? proc)
               self-label (eq? (lexical-ref-gensym proc) self-label)
-              (eq? context 'tail))
-         (let lp ((lcase (lambda-body self)))
-           (cond
-            ((and (lambda-case? lcase)
+              (eq? context 'tail)
               (not (lambda-case-kw lcase))
               (not (lambda-case-rest lcase))
               (= (length args)
                  (+ (length (lambda-case-req lcase))
                     (or (and=> (lambda-case-opt lcase) length) 0))))
-             ;; we have a case that matches the args; evaluate new
-             ;; values, rename variables and goto the case label
          (for-each comp-push args)
          (for-each (lambda (sym)
                      (pmatch (hashq-ref (hashq-ref allocation sym) self)
@@ -447,16 +444,6 @@
                        (,x (error "bad lambda-case arg allocation" x))))
                    (reverse (lambda-case-gensyms lcase)))
          (emit-branch src 'br (car (hashq-ref allocation lcase))))
-            ((lambda-case? lcase)
-             ;; no match, try next case
-             (lp (lambda-case-alternate lcase)))
-            (else
-             ;; no cases left -- use the normal tail call mechanism. we
-             ;; can't just shuffle the args down and jump back to the
-             ;; self label, because we don't have space.
-             (comp-push proc)
-             (for-each comp-push args)
-             (emit-code src (make-glil-call 'tail-call (length args)))))))
         
         ;; lambda, the ultimate goto
         ((and (lexical-ref? proc)
@@ -780,7 +767,8 @@
          (if alternate-label
              (begin
                (emit-label alternate-label)
-               (comp-tail alternate)))))
+               (flatten-lambda-case alternate allocation self self-label
+                                    fix-labels emit-code)))))
       
       ((<let> src names gensyms vals body)
        (for-each comp-push vals)

test-suite/tests/compiler.test

@@ -1,5 +1,5 @@
 ;;;; compiler.test --- tests for the compiler      -*- scheme -*-
-;;;; Copyright (C) 2008, 2009, 2010 Free Software Foundation, Inc.
+;;;; Copyright (C) 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
 ;;;; 
 ;;;; This library is free software; you can redistribute it and/or
 ;;;; modify it under the terms of the GNU Lesser General Public
@@ -149,3 +149,18 @@
                                        ((y)   y)
                                        ((y z) (list y z)))))))
         (not (not (memv 0 (map source:addr s))))))))
+
+(with-test-prefix "case-lambda"
+  (pass-if "self recursion to different clause"
+    (equal? (with-output-to-string
+              (lambda ()
+                (let ()
+                  (define t
+                    (case-lambda
+                      ((x)
+                       (t x 'y))
+                      ((x y)
+                       (display (list x y))
+                       (list x y))))
+                  (display (t 'x)))))
+            "(x y)(x y)")))