11502 - Alpha/Linux doesn't like denormalized values either.

Status: VERIFIED DUPLICATE of bug 9967

(Core :: JavaScript Engine, defect, P3)

Description

[Rick Niles]

While you carefully check for INF and NAN you never checked for
denormalized values in your double precision checks.  With all the
infrastructure in place it was trival to add it.  Alpha/Linux with
glibc-2.1 requires this patch:

--- jsnum.h	Mon Aug  9 22:43:45 1999
+++ jsnum.h.new	Mon Aug  9 22:43:28 1999
@@ -57,6 +57,10 @@ JS_BEGIN_EXTERN_C
 #define JSDOUBLE_IS_NEGZERO(d)  (JSDOUBLE_HI32(d) == JSDOUBLE_HI32_SIGNBIT && \
 				 JSDOUBLE_LO32(d) == 0)

+#define JSDOUBLE_IS_DENORMAL(x)                                               \
+    ((JSDOUBLE_HI32(x) & JSDOUBLE_HI32_EXPMASK) == 0 &&                       \
+    (JSDOUBLE_LO32(x) || (JSDOUBLE_HI32(x) & JSDOUBLE_HI32_MANTMASK)))

 /*
  * JSDOUBLE_IS_INT first checks that d is neither NaN nor infinite, to avoid
  * raising SIGFPE on platforms such as Alpha Linux, then (only if the cast is
@@ -64,7 +68,7 @@ JS_BEGIN_EXTERN_C
  * comparisons under MSVC.
  */
 #define JSDOUBLE_IS_INT(d, i) (JSDOUBLE_IS_FINITE(d) && !JSDOUBLE_IS_NEGZERO(d)
\
-			       && ((d) == (i = (jsint)(d))))
+			       && !JSDOUBLE_IS_DENORMAL(d) && ((d) == (i = (jsint)(d))))

 /* Initialize the Number class, returning its prototype object. */
 extern JSObject *

Comment 1

[Mike McCabe]

Denormalized values are part of the JavaScript language standard, and have been
with the language since very early on.  (Waldemar, Brendan - can you confirm?)

This issue has come up before with various OSes running on the Alpha; the proper
solution is to add a compiler flag to turn off floating point exceptions; I
belive the proper flag is -mieee.  If you can find a clean place to incorporate
that flag into the make system (possibly including the standalone 'Makefile.ref'
file for the JavaScript shell) I'd be happy to apply a patch.

Comment 2

[Mike McCabe]

Marking as depending on 9967, and reopening; I think I was a little rash in
closing it.  The fact that we need to suppress floating point exceptions for the
Alpha architecture remains.

Comment 3

[Mike McCabe]

Here we go.  Now that it's open, I can mark it as a dup of 9967.  Sorry for the
excess traffic, cc list.

*** This bug has been marked as a duplicate of 9967 ***

Comment 4

[Jay Patel [:jay]]

verified dup...see Bug 9967

Comment 5

[Brendan Eich [:brendan]]

Is this really a DUP, or do we need something like fpsetmask(0) called early in
main on Linux/Alpha as well as on FreeBSD/Intel?

/be

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/b68b85411df6
[fenix] For https://github.com/mozilla-mobile/fenix/issues/11502: Make sure to always process root titles for parent folders during edit