[Bug target/27627] __builtin_nanf("") doesn't return a _quiet_ nan on parisc

[soete dot joel at tiscali dot be]

------- Comment #5 from soete dot joel at tiscali dot be  2006-05-17 08:56 -------
Created an attachment (id=11481)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11481&action=view)
just another similar test case regarding double equivalent pb

compile with -O2 the Nan3.s is:
 .LEVEL 1.1
 .section .rodata.str1.4,"aMS",@progbits,1
 .align 4
.LC1:
.stringz"__builtin_nan(): 0x%llx.\n"
 .section .rodata.cst8,"aM",@progbits,8
 .align 8
.LC0:
 .word 2146959360
 .word 0
 .text
 .align 4
.globl main
 .type main, @function
main:
 .PROC
 .CALLINFO FRAME=0,CALLS,SAVE_RP
 .ENTRY
 stw %r2,-20(%r30)
 ldil LR'.LC0,%r28
 ldil LR'.LC1,%r26
 ldw RR'.LC0(%r28),%r23
 ldw RR'.LC0+4(%r28),%r24
 ldo RR'.LC1(%r26),%r26
 ldw -20(%r30),%r2
 bl printf,%r0
 nop
 nop
 .EXIT
 .PROCEND
 .size main, .-main
 .ident "GCC: (GNU) 4.1.1 20060511 (prerelease) (Debian 4.1.0-4)"

and print out:
__builtin_nan(): 0x7ff8000000000000.

or bin form of 1 32bit word: 01111111111110000000000000000000

i.e.
- the first bit being the sign == 0
- next 11 being the exponenent all == 1
- next 52 one being fraction have the first bit == 1, making this NAN a
signaling NAN.

And according to this thread (I don't have access to C99 std ;-( ):
<http://gcc.gnu.org/ml/libstdc++/2002-09/msg00030.html>
as well as gcc info
/quote
 -- Built-in Function: double __builtin_nan (const char *str)
     This is an implementation of the ISO C99 function `nan'.

     Since ISO C99 defines this function in terms of `strtod', which we
     do not implement, a description of the parsing is in order.  The
     string is parsed as by `strtol'; that is, the base is recognized by
     leading `0' or `0x' prefixes.  The number parsed is placed in the
     significand such that the least significant bit of the number is
     at the least significant bit of the significand.  The number is
     truncated to fit the significand field provided.  The significand
     is forced to be a quiet NaN.

     This function, if given a string literal, is evaluated early enough
     that it is considered a compile-time constant.
/quote

__builtin_nan[f](""); should return a quiet NAN. To do so, the parisc2.0 doc,
says that the fraction part have to be <> 0 but with first bit == 0.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27627