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[Bug optimization/14907] New: bogus sign/zero extension when relaying parameters with regparm
- From: "cesarb at nitnet dot com dot br" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 10 Apr 2004 14:05:07 -0000
- Subject: [Bug optimization/14907] New: bogus sign/zero extension when relaying parameters with regparm
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
(this seem to be another case of the general bug of "the compiler doesn't know
when it has already extended the value")
This is the "other side" of PR 14903
When compiling:
extern void __attribute__((__regparm__(3))) f(unsigned char x);
void __attribute__((__regparm__(3))) g(unsigned char x) { f(x); }
With:
gcc -W -Wall -Os -fomit-frame-pointer -save-temps -c
The result is:
g:
movzbl %al, %eax
jmp f
Notice again the bogus zero extension (sign extension with signed char). The
same happens with shorts.
While PR 14903 can cause excessive stack usage, this one just looks dumb in the
assembly output.
Reading specs from /usr/lib/gcc-lib/i486-linux/3.3.3/specs
Configured with: ../src/configure -v
--enable-languages=c,c++,java,f77,pascal,objc,ada,treelang --prefix=/usr
--mandir=/usr/share/man --infodir=/usr/share/info
--with-gxx-include-dir=/usr/include/c++/3.3 --enable-shared --with-system-zlib
--enable-nls --without-included-gettext --enable-__cxa_atexit
--enable-clocale=gnu --enable-debug --enable-java-gc=boehm
--enable-java-awt=xlib --enable-objc-gc i486-linux
Thread model: posix
gcc version 3.3.3 (Debian 20040401)
--
Summary: bogus sign/zero extension when relaying parameters with
regparm
Product: gcc
Version: 3.3.3
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: cesarb at nitnet dot com dot br
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14907