Revert "Remove workaround for 9.2 compiler bug."

This reverts commit 7828111b77fb53e34b365abc775148f49eabe1d2.

I haven't tracked this down because the stack trace is full of frames
in the compiler for which we don't install debug data but the symptom
is:

;  Compiling file: "./floenv.bin" => "./floenv.com"...
;The object +inf.0, passed as the first argument to flonum-normalize, is not the correct type.

First few frames suggest this is in flo:->rational called by something
in RTL CSE.

diff --git a/src/runtime/floenv.scm b/src/runtime/floenv.scm
index 3c78ef5b590e8619829966cb3bacb7fea41c6883..d4d478ee372a2f6062fc683f4c6401092e191cd0 100644 (file)
--- 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