Re: c++/3834: const volatile G++ bug gcc-2.95.2 sparc-sun-solaris2.5.1

Re: c++/3834: const volatile G++ bug gcc-2.95.2 sparc-sun-solaris2.5.1

[davem]

Synopsis: const volatile G++ bug gcc-2.95.2 sparc-sun-solaris2.5.1

State-Changed-From-To: open->closed
State-Changed-By: davem
State-Changed-When: Fri May  3 14:57:50 2002
State-Changed-Why:
    Retesting with gcc-3.1 CVS shows that the compiler respects
    the volatile attribute in both the second and third loop
    which appears to be what you think should happen.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=3834

c++/3834: const volatile G++ bug gcc-2.95.2 sparc-sun-solaris2.5.1

[don]

>Number:         3834
>Category:       c++
>Synopsis:       const volatile G++ bug gcc-2.95.2 sparc-sun-solaris2.5.1
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Thu Jul 26 10:56:01 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     Donald Duncan
>Release:        gcc version 2.95.2 19991024 (release)
>Organization:
>Environment:
sparc-sun-solaris2.5.1
>Description:
The first loop is correct (if nonsensical),
The second is correct, but
the third should look like the second
while it looks like the first!
Volatile has been lost and const prevails.

In the assembly, the line after .LL46 tests
a register but does not update its contents
inside the loop (LL46 & next 5 lines of assembly).

The second loop (LL48) works correctly as
there is a ld instruction getting new data.
(This is a 6 line code generation.)

The third loop (LL51) does not have the
data load instruction like the second loop.
(Should be 6 lines but only 5 lines of code.)
THIS IS THE BUG I FOUND.

I do not know if removing some of the C++
layers in the source will make a difference
to the code generated. I simply tried to
closely match the actual code in my source.

>How-To-Repeat:

/hq/master/util/gcc-2.95.2/bin/g++ -save-temps -S -fverbose-asm -Wall -O
3 gccbug.cxx
>Fix:

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