From 0fbe3181f7630cf1258bf019fce0504728bdb9f8 Mon Sep 17 00:00:00 2001
From: Taylor R Campbell <campbell@mumble.net>
Date: Sat, 20 Apr 2019 19:48:07 +0000
Subject: [PATCH] Simplify some logic by using dedicated scratch registers or
 targets.

No need to allocate temporaries except when we need more than two or
three of them.
---
 src/compiler/machines/aarch64/rules2.scm | 15 +++------------
 src/compiler/machines/aarch64/rules3.scm |  4 ++--
 src/compiler/machines/aarch64/rulfix.scm | 11 ++++++-----
 3 files changed, 11 insertions(+), 19 deletions(-)

diff --git a/src/compiler/machines/aarch64/rules2.scm b/src/compiler/machines/aarch64/rules2.scm
index 382030ebb..1d555f976 100644
--- a/src/compiler/machines/aarch64/rules2.scm
+++ b/src/compiler/machines/aarch64/rules2.scm
@@ -80,20 +80,11 @@ USA.
 
 (define-rule predicate
   (PRED-1-ARG INDEX-FIXNUM? (REGISTER (? register)))
-  (define (operate temp source)
+  (let* ((source (standard-source! register))
+         (temp regnum:scratch-0))
     (set-equal-branches!)
     (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)))))
+         (CMP X ,temp (&U ,(* 2 type-code:fixnum))))))
 
 (define (zero-test! register)
   (set-equal-zero-branches! register)
diff --git a/src/compiler/machines/aarch64/rules3.scm b/src/compiler/machines/aarch64/rules3.scm
index 6756f022e..37ed22954 100644
--- a/src/compiler/machines/aarch64/rules3.scm
+++ b/src/compiler/machines/aarch64/rules3.scm
@@ -307,8 +307,8 @@ USA.
   (assert (>= frame-size 2))
   (assert (fits-in-unsigned-12? (* 8 frame-size))) ;XXX
   (assert (= 8 address-units-per-object))
-  (let* ((temp1 (allocate-temporary-register! 'GENERAL))
-         (temp2 (allocate-temporary-register! 'GENERAL))
+  (let* ((temp1 regnum:scratch-0)
+         (temp2 regnum:scratch-1)
          (index (allocate-temporary-register! 'GENERAL))
          (label (generate-label 'MOVE-LOOP))
          ;; Unroll an odd element if there is one; then do an even
diff --git a/src/compiler/machines/aarch64/rulfix.scm b/src/compiler/machines/aarch64/rulfix.scm
index 8d753b354..b9e30a595 100644
--- a/src/compiler/machines/aarch64/rulfix.scm
+++ b/src/compiler/machines/aarch64/rulfix.scm
@@ -172,8 +172,9 @@ USA.
     (if (not overflow?)
         (LAP (ASR X ,regnum:scratch-0 ,source1 (&U ,scheme-type-width))
              (MUL X ,target ,regnum:scratch-0 ,source2))
-        (let* ((mask (allocate-temporary-register! 'GENERAL))
-               (hi (allocate-temporary-register! 'GENERAL)))
+        (let* ((mask regnum:scratch-0)
+               (hi regnum:scratch-1)
+               (temp (allocate-temporary-register! 'GENERAL)))
           ;; We're going to test whether the high 64-bits is equal to
           ;; the -1 or 0 we expect it to be.  Overflow if not equal, no
           ;; overflow if equal.
@@ -186,9 +187,9 @@ USA.
                (CSETM X LT ,mask)
                (CMP X ,source2 (&U 0))
                (CINV X LT ,mask ,mask)
-               (ASR X ,regnum:scratch-0 ,source1 (&U ,scheme-type-width))
-               (SMULH X ,hi ,regnum:scratch-0 ,source2)
-               (MUL X ,target ,regnum:scratch-0 ,source2)
+               (ASR X ,temp ,source1 (&U ,scheme-type-width))
+               (SMULH X ,hi ,temp ,source2)
+               (MUL X ,target ,temp ,source2)
                (CMP X ,mask ,hi))))))
 
 (define-arithmetic-method 'FIXNUM-QUOTIENT fixnum-methods/2-args
-- 
2.25.1