c/7277: Casting integers to vector types causes internal compiler error

hakonrk@fys.uio.no hakonrk@fys.uio.no
Thu Jul 11 07:30:00 GMT 2002


>Number:         7277
>Category:       c
>Synopsis:       Casting integers to vector types causes internal compiler error
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          ice-on-legal-code
>Submitter-Id:   net
>Arrival-Date:   Thu Jul 11 07:06:00 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     Haakon Riiser
>Release:        3.1
>Organization:
University of Oslo
>Environment:
System: Linux s 2.4.18 #2 Thu Jun 6 00:23:32 CEST 2002 i686 unknown
Distribution: Slackware 8.1
Architecture: i686

host: i686-pc-linux-gnu
build: i686-pc-linux-gnu
target: i686-pc-linux-gnu
configured with: /local/build/gcc/gcc-3.1/configure --prefix=/usr/local/gcc-3.1 --enable-languages=c --disable-nls
>Description:
Casting integers into vector types (of the same size) causes
internal compiler errors.  The following illustrates what happens
when casting from a constant integer (code shown in How-To-Repeat):

##############################################################################
$ gcc -v -c -mmmx cast.c
Reading specs from /usr/local/gcc-3.1/lib/gcc-lib/i686-pc-linux-gnu/3.1/specs
Configured with: /local/build/gcc/gcc-3.1/configure --prefix=/usr/local/gcc-3.1 --enable-languages=c --disable-nls
Thread model: single
gcc version 3.1
 /usr/local/gcc-3.1/lib/gcc-lib/i686-pc-linux-gnu/3.1/cc1 -lang-c -v -D__GNUC__=3 -D__GNUC_MINOR__=1 -D__GNUC_PATCHLEVEL__=0 -D__ELF__ -Dunix -D__gnu_linux__ -Dlinux -D__ELF__ -D__unix__ -D__gnu_linux__ -D__linux__ -D__unix -D__linux -Asystem=posix -D__NO_INLINE__ -D__STDC_HOSTED__=1 -Acpu=i386 -Amachine=i386 -Di386 -D__i386 -D__i386__ -D__tune_i686__ -D__tune_pentiumpro__ cast.c -quiet -dumpbase cast.c -mmmx -version -o /tmp/cc2ubmWE.s
GNU CPP version 3.1 (cpplib) (i386 Linux/ELF)
GNU C version 3.1 (i686-pc-linux-gnu)
	compiled by GNU C version 3.1.
ignoring nonexistent directory "/usr/local/gcc-3.1/i686-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/local/gcc-3.1/include
 /usr/local/gcc-3.1/lib/gcc-lib/i686-pc-linux-gnu/3.1/include
 /usr/include
End of search list.
cast.c: In function `null':
cast.c:6: Internal compiler error in output_constant_pool, at varasm.c:4064
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://www.gnu.org/software/gcc/bugs.html> for instructions.
##############################################################################

When casting from a non-volatile variable, a new ICE appears if
and only if optimization is enabled:

Internal compiler error in subst, at combine.c:3546

This ICE will also manifest itself if one tries to trick the
compiler by using a union of "long long" and "v8qi", assigning
to the "long long" variable and returning the "v8qi" variable.
Again, the ICE only appears when optimization is enabled.
>How-To-Repeat:
# 1 "cast.c"
typedef int v8qi __attribute__ ((mode(V8QI)));

v8qi null(void)
{
        return (v8qi) 0LL;
}
>Fix:
Work-around: Use a volatile temporary variable:

/****************************************************************************/
typedef int v8qi __attribute__ ((mode(V8QI)));

v8qi null(void)
{
	volatile long long tmp = 0LL;
        return (v8qi) tmp;
}
/****************************************************************************/
>Release-Note:
>Audit-Trail:
>Unformatted:



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