c++/1090: g++ 20001218 generates wrong optimized code on alpha

[ovi at physics dot utoronto dot ca]

>Number:         1090
>Category:       c++
>Synopsis:       g++ 20001218 generates wrong optimized code on alpha
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Mon Dec 18 16:16:01 PST 2000
>Closed-Date:
>Last-Modified:
>Originator:     ovi@physics.utoronto.ca
>Release:        gcc version 2.97 20001218 (experimental)
>Organization:
>Environment:
Redhat 7.0 for alpha
Linux seahawk.physics.utoronto.ca 2.2.17-ovi #3 Sat Dec 9 23:22:58 EST 2000 alpha unknown
g++ -c -O1 -v -save-temps main.cc
Reading specs from /usr/local/Packages/lang/gcc/gcc.head/install/lib/gcc-lib/alphaev6-unknown-linux-gnu/2.97/specs
Configured with: ../gcc/configure --prefix=/usr/local/Packages/lang/gcc/gcc.head/install --enable-languages=c++ --enable-shared --enable-haifa --disable-nls : (reconfigured)  : (reconfigured) ../gcc/configure --prefix=/usr/local/Packages/lang/gcc/gcc.head/install --enable-languages=c++ --enable-shared --enable-haifa --disable-nls
gcc version 2.97 20001218 (experimental)
 /usr/local/Packages/lang/gcc/gcc.head/install/lib/gcc-lib/alphaev6-unknown-linux-gnu/2.97/cpp0 -lang-c++ -D__GNUG__=2 -D__GXX_ABI_VERSION=100 -v -iprefix /usr/local/bin/../lib/gcc-lib/alphaev6-unknown-linux-gnu/2.97/ -D__GNUC__=2 -D__GNUC_MINOR__=97 -D__GNUC_PATCHLEVEL__=0 -Dlinux -Dunix -D_LONGLONG -D__alpha__ -D__ELF__ -D__linux__ -D__unix__ -D_LONGLONG -D__alpha__ -D__ELF__ -D__linux -D__unix -Asystem=linux -D__OPTIMIZE__ -D__STDC_HOSTED__=1 -D__LANGUAGE_C_PLUS_PLUS__ -D__LANGUAGE_C_PLUS_PLUS -D__cplusplus -Acpu=alpha -Amachine=alpha -D__alpha -D__alpha__ -D__alpha_ev6__ -Acpu=ev6 -D__alpha_bwx__ -Acpu=bwx -D__alpha_max__ -Acpu=max -D__alpha_fix__ -Acpu=fix main.cc main.ii
GNU CPP version 2.97 20001218 (experimental) (cpplib) (Alpha GNU/Linux for ELF)
ignoring nonexistent directory "/usr/local/include/g++-v3"
ignoring nonexistent directory "/usr/local/lib/gcc-lib/alphaev6-unknown-linux-gnu/2.97/include"
ignoring nonexistent directory "/usr/local/alphaev6-unknown-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/Packages/lang/gcc/gcc.head/install/include/g++-v3
 /usr/local/include
 /usr/local/Packages/lang/gcc/gcc.head/install/lib/gcc-lib/alphaev6-unknown-linux-gnu/2.97/include
 /usr/local/Packages/lang/gcc/gcc.head/install/alphaev6-unknown-linux-gnu/include
 /usr/include
End of search list.
 /usr/local/Packages/lang/gcc/gcc.head/install/lib/gcc-lib/alphaev6-unknown-linux-gnu/2.97/cc1plus -fpreprocessed main.ii -quiet -dumpbase main.cc -O1 -version -fnew-abi -o main.s
....
>Description:
When compiled with -O0
ovi:seahawk:bug3>> exe
n is 1   a = 7

When compiled with -O1
ovi:seahawk:bug3>> exe
n is 4875744     a = 7

The problem disappears when line:
  E << n;
is commented out or line:
  c = 0;while( n%5  == 0 ){c += 1;n /= 5;}
is commented out.

gcc 2.95.2.1 generates correct code.
>How-To-Repeat:
See attachment. Compare the output of the executable 
compiled with -O0 and -O1. 
>Fix:

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