[MLton-commit] r4690

[Stephen Weeks]

Fixed bug in the "useless" SSA optimization pass, caused by calling an
imported C function and then ignoring the result.  The useless pass
eliminated the result, which changed the return type of the call, and
led to a type error.  The fix was simply to force FFI arguments and
results to be useful.


----------------------------------------------------------------------

U   mlton/trunk/doc/changelog
U   mlton/trunk/mlton/ssa/useless.fun

----------------------------------------------------------------------

Modified: mlton/trunk/doc/changelog
===================================================================
--- mlton/trunk/doc/changelog	2006-07-19 02:50:56 UTC (rev 4689)
+++ mlton/trunk/doc/changelog	2006-08-04 05:48:22 UTC (rev 4690)
@@ -1,5 +1,9 @@
 Here are the changes since version 20051202.
 
+* 2006-08-03
+   - Fixed a bug in the "useless" SSA optimization, caused by calling
+     an imported C function and then ignoring the result.
+
 * 2006-06-24
    - Fixed a bug in pass to flatten data structures.  Thanks to Joe Hurd
      for the bug report.

Modified: mlton/trunk/mlton/ssa/useless.fun
===================================================================
--- mlton/trunk/mlton/ssa/useless.fun	2006-07-19 02:50:56 UTC (rev 4689)
+++ mlton/trunk/mlton/ssa/useless.fun	2006-08-04 05:48:22 UTC (rev 4690)
@@ -520,6 +520,9 @@
                                (unify (l, l'); unifySlot (e, e'))
                            | _ => Error.bug "Useless.primApp: Array_toVector")
                    | Array_update => update ()
+                   | FFI _ =>
+                        (Vector.foreach (args, deepMakeUseful);
+                         deepMakeUseful result)
                    | MLton_equal => Vector.foreach (args, deepMakeUseful)
                    | Ref_assign => coerce {from = arg 1, to = deref (arg 0)}
                    | Ref_deref => return (deref (arg 0))