middle-end/6205: -O -fpmath=sse breaks visibility of register accumulated sum

[tprince@computer.org]

>Number:         6205
>Category:       middle-end
>Synopsis:       -O -fpmath=sse breaks visibility of register accumulated sum
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Apr 06 07:16:00 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     Tim Prince
>Release:        3.1
>Organization:
>Environment:
linux-SuSE 7.3 or cygwin/2K
>Description:
result of a float sum in SSE register is seen as NaN in certain contexts, when built with -O -mfpmath=sse

Problem originally seen in larger examples in g77; case available on request.

>How-To-Repeat:
gcc -O -march=pentium3 -mfpmath=sse badsum.c
./a.out

result seen as nan in printf(), but is OK if -O or -mfpmath options are removed
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
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