From: Taylor R Campbell <campbell@mumble.net>
Date: Sat, 17 Nov 2018 09:15:26 +0000 (+0000)
Subject: Revert "Remove workaround for 9.2 compiler bug."
X-Git-Tag: mit-scheme-pucked-10.1.2~16^2~57
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=7cbf0d42c187ef96fc861a43ceff42f68ca53741;p=mit-scheme.git

Revert "Remove workaround for 9.2 compiler bug."

This reverts commit 7828111b77fb53e34b365abc775148f49eabe1d2.

Can't keep this change until a new release has a compiler without
the bug.
---

diff --git a/src/runtime/floenv.scm b/src/runtime/floenv.scm
index 3c78ef5b5..d4d478ee3 100644
--- a/src/runtime/floenv.scm
+++ b/src/runtime/floenv.scm
@@ -362,27 +362,30 @@ USA.
 (define flo:nan.0)
 (define flo:+inf.0)
 (define flo:-inf.0)
-(if (flo:have-trap-enable/disable?)
-    (begin
-      (set! flo:nan.0
-	    (named-lambda (flo:nan.0)
-	      (flo:with-exceptions-untrapped (flo:exception:invalid-operation)
-		(lambda ()
-		  (flo:/ 0. 0.)))))
-      (set! flo:+inf.0
-	    (named-lambda (flo:+inf.0)
-	      (flo:with-exceptions-untrapped (flo:exception:divide-by-zero)
-		(lambda ()
-		  (flo:/ +1. 0.)))))
-      (set! flo:-inf.0
-	    (named-lambda (flo:-inf.0)
-	      (flo:with-exceptions-untrapped (flo:exception:divide-by-zero)
-		(lambda ()
-		  (flo:/ -1. 0.)))))
-      unspecific)
-    ;; This works on macOS.  YMMV.
-    (begin
-      (set! flo:nan.0 (named-lambda (flo:nan.0) (flo:/ 0. 0.)))
-      (set! flo:+inf.0 (named-lambda (flo:+inf.0) (flo:/ +1. 0.)))
-      (set! flo:-inf.0 (named-lambda (flo:-inf.0) (flo:/ -1. 0.)))
-      unspecific))
\ No newline at end of file
+;;; ZERO can be eliminated after 9.3 is released.  It works around
+;;; overly-aggressive constant folding in SF and LIAR.
+(let ((zero (lambda () (identity-procedure 0.))))
+  (if (flo:have-trap-enable/disable?)
+      (begin
+	(set! flo:nan.0
+	      (named-lambda (flo:nan.0)
+		(flo:with-exceptions-untrapped (flo:exception:invalid-operation)
+		  (lambda ()
+		    (flo:/ 0. (zero))))))
+	(set! flo:+inf.0
+	      (named-lambda (flo:+inf.0)
+		(flo:with-exceptions-untrapped (flo:exception:divide-by-zero)
+		  (lambda ()
+		    (flo:/ +1. (zero))))))
+	(set! flo:-inf.0
+	      (named-lambda (flo:-inf.0)
+		(flo:with-exceptions-untrapped (flo:exception:divide-by-zero)
+		  (lambda ()
+		    (flo:/ -1. (zero))))))
+	unspecific)
+      ;; This works on macOS.  YMMV.
+      (begin
+	(set! flo:nan.0 (named-lambda (flo:nan.0) (flo:/ 0. (zero))))
+	(set! flo:+inf.0 (named-lambda (flo:+inf.0) (flo:/ +1. (zero))))
+	(set! flo:-inf.0 (named-lambda (flo:-inf.0) (flo:/ -1. (zero))))
+	unspecific)))
\ No newline at end of file