compiler: move peephole pattern and remove condition.

* stdlib/optimize.tl (basic-blocks do-peephole-block):
Remove the local function only-locally-used-treg.
This is unnecessary because the optimization is valid
even if the treg is used in downstream basic blocks.
It was necessary previously in the old version of
this optimization in which we deleted the first
instruction which sets the treg's value. We are now
depending on it being identified as a dead register.
Also, moving the rule to the end. The reason is
that there are cases when the pattern matches, but
it returns insns. That causes the rewrite macro to
march down to the next instruction, skipping other
patterns. This could be bad, unless the pattern is the
last one tried before the @else fallback.

1 files changed, 11 insertions, 15 deletions

diff --git a/stdlib/optimize.tl b/stdlib/optimize.tl
index bb1b84c3..e78c9300 100644
--- a/stdlib/optimize.tl
+++ b/stdlib/optimize.tl
@@ -384,10 +384,7 @@
 (defmeth basic-blocks do-peephole-block (bb bl code)
   (labels ((dead-treg (insn n)
              (let ((li [bb.li-hash insn]))
-               (and li (not (bit li.used n)))))
-           (only-locally-used-treg (insn n)
-             (let ((li [bb.li-hash insn]))
-               (and li (bit li.used n) (not (bit bl.live n))))))
+               (and li (not (bit li.used n))))))
     (rewrite-case insns code
       ;; dead t-reg
       (@(require ((@(or mov getlx getv getf getfb) (t @n) . @nil) . @nil)
@@ -407,17 +404,6 @@
         (pushnew bl bb.rescan)
         (set bb.recalc t)
         (cdr insns))
-      ;; unnecessary copying t-reg
-      (@(require ((mov @(as dst (t @n)) @src) . @rest)
-                 (only-locally-used-treg (car insns) n)
-                 (nequal dst src))
-        (let ((ren bb.(rename rest dst src)))
-          (cond
-            ((nequal rest ren)
-             (pushnew bl bb.rescan)
-             (set bb.recalc t)
-             (cons (car insns) ren))
-            (t insns))))
       ;; wasteful moves
       (((mov @reg0 @nil) (mov @reg0 @nil) . @nil)
        (cdr insns))
@@ -500,6 +486,16 @@
                 bl.next nil
                 bl.links nil))
          oinsns))
+      ;; unnecessary copying t-reg
+      (@(require ((mov @(as dst (t @nil)) @src) . @rest)
+                 (nequal dst src))
+        (let ((ren bb.(rename rest dst src)))
+          (cond
+            ((nequal rest ren)
+             (pushnew bl bb.rescan)
+             (set bb.recalc t)
+             (cons (car insns) ren))
+            (t insns))))
       (@nil insns))))
 
 (defmeth basic-blocks peephole (bb)