From: Taylor R Campbell <campbell@mumble.net>
Date: Tue, 15 Jan 2019 03:19:18 +0000 (+0000)
Subject: Avoid REGISTER-COPY-IF-AVAILABLE and TEMPORARY-COPY-IF-AVAILABLE.
X-Git-Tag: mit-scheme-pucked-10.1.20~11^2~66^2~83
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=136919dcd09d3ef54d9890d41576b1999bc2bc54;p=mit-scheme.git

Avoid REGISTER-COPY-IF-AVAILABLE and TEMPORARY-COPY-IF-AVAILABLE.

These give out register references, which are a pain.  Just use
REUSE-PSEUDO-REGISTER-IF-AVAILABLE! to get the machine register
number.
---

diff --git a/src/compiler/machines/aarch64/rules1.scm b/src/compiler/machines/aarch64/rules1.scm
index 55dcfe73c..a75955d84 100644
--- a/src/compiler/machines/aarch64/rules1.scm
+++ b/src/compiler/machines/aarch64/rules1.scm
@@ -43,25 +43,24 @@ USA.
   (ASSIGN (REGISTER (? target))
           (CONS-POINTER (REGISTER (? type))
                         (REGISTER (? datum))))
-  (cond ((let ((type (register-known-value type)))
-           (and type (zero? type)))
-         (assign-register->register target datum))
-        ((register-copy-if-available datum 'GENERAL target)
-         => (lambda (get-target!)
-              ;; If we already have a suitable register for the target,
-              ;; use bit field insertion to set the type.
-              (let* ((type (standard-source! type))
-                     (target (get-target!))
-                     (lsb scheme-datum-width)
-                     (width scheme-type-width))
-                (LAP (BFI X ,target ,type (&U ,lsb) (&U ,width))))))
-        (else
-         ;; Otherwise, no advantage to using bit field insertion since
-         ;; we'd need two instructions anyway, so just shift and or.
-         (standard-binary target type datum
-           (lambda (target type datum)
-             (LAP (LSL X ,target ,type (&U ,scheme-datum-width))
-                  (ORR X ,target ,target ,datum)))))))
+  (reuse-pseudo-register-alias! datum 'GENERAL
+    (lambda (alias)
+      ;; If we already have a reusable machine register loaded with the
+      ;; datum, use bit field insertion to set the type, and treat it
+      ;; as an alias for the target.
+      (let ((type (standard-source! type))
+            (lsb scheme-datum-width)
+            (width scheme-type-width))
+        (delete-dead-registers!)
+        (add-pseudo-register-alias! target alias)
+        (LAP (BFI X ,alias ,type (&U ,lsb) (&U ,width)))))
+    (lambda ()
+      ;; No advantage to using bit field insertion since we'd need two
+      ;; instructions anyway, so just shift and or.
+      (standard-binary target type datum
+        (lambda (target type datum)
+          (LAP (LSL X ,target ,type (&U ,scheme-datum-width))
+               (ORR X ,target ,target ,datum)))))))
 
 (define-rule statement
   (ASSIGN (REGISTER (? target))
diff --git a/src/compiler/machines/aarch64/rules2.scm b/src/compiler/machines/aarch64/rules2.scm
index bef249b29..382030ebb 100644
--- a/src/compiler/machines/aarch64/rules2.scm
+++ b/src/compiler/machines/aarch64/rules2.scm
@@ -80,10 +80,20 @@ USA.
 
 (define-rule predicate
   (PRED-1-ARG INDEX-FIXNUM? (REGISTER (? register)))
-  (let ((temp (standard-move-to-temporary! register)))
+  (define (operate temp source)
     (set-equal-branches!)
-    (LAP (LSR X ,temp (&U ,(- scheme-datum-width 1)))
-         (CMP X ,temp (&U ,(* 2 type-code:fixnum))))))
+    (LAP (LSR X ,temp ,source (&U ,(- scheme-datum-width 1)))
+         (CMP X ,temp (&U ,(* 2 type-code:fixnum)))))
+  ;; This basically is WITH-TEMPORARY-REGISTER-COPY! but without
+  ;; register references getting in the way.
+  (reuse-pseudo-register-alias! register 'GENERAL
+    (lambda (temp)
+      (need-register! temp)
+      (operate temp temp))
+    (lambda ()
+      (let* ((source (standard-source! register))
+             (temp (allocate-temporary-register! 'GENERAL)))
+        (operate temp source)))))
 
 (define (zero-test! register)
   (set-equal-zero-branches! register)