target/2246: Code generated for IA64 doesn't reset NaT bit on scratch reg

[wilson@gcc.gnu.org]

Synopsis: Code generated for IA64 doesn't reset NaT bit on scratch reg

Responsible-Changed-From-To: unassigned->wilson
Responsible-Changed-By: wilson
Responsible-Changed-When: Mon Sep 17 21:23:08 2001
Responsible-Changed-Why:
    IA-64 maintainer
State-Changed-From-To: open->analyzed
State-Changed-By: wilson
State-Changed-When: Mon Sep 17 21:23:08 2001
State-Changed-Why:
    The only way to fix this problem is to initialize all
    local variables when they are declared.  Gcc does not
    have infrastructure to do this at the moment, so this
    will require development work.  There is also a concern
    that this will result in redundant stores that the optimizer
    may not be able to eliminate, and thus may result in a
    performance regression.  Additional optimizations may
    be necessary to avoid this problem.
    
    As yet, this has not been observed to cause problems on
    ia64-linux, primarily because gcc does not have speculation
    support, and thus we never set the NAT bit.  This has been
    observed to cause problems on HPUX, as the HPUX compiler
    does use speculation, and thus the NAT bit can be set.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&pr=2246&database=gcc