[Bug target/29776] New: result of ffs/clz/ctz/popcount/parity are already sign-extended

["dean at arctic dot org" <gcc-bugzilla at gcc dot gnu dot org>]

unfortunately the ffs/clz/ctz/popcount/parity builtins are defined to return
signed types despite the fact they are either undefined or return a
non-negative integer.  as a result unnecessary sign extension occurs.  for
example in this case the result of bsf could be used directly in the mask[]
index.

-dean

% cat ctz.c
unsigned mask[8];

unsigned foo(unsigned y, unsigned char x)
{
  return y & mask[__builtin_ctz(x)];
}
% ~/gcc/bin/gcc -g -O3 -Wall -c ctz.c
% objdump -dr ctz.o

ctz.o:     file format elf64-x86-64

Disassembly of section .text:

0000000000000000 <foo>:
   0:   40 0f b6 f6             movzbl %sil,%esi
   4:   0f bc f6                bsf    %esi,%esi
   7:   48 63 f6                movslq %esi,%rsi
   a:   23 3c b5 00 00 00 00    and    0x0(,%rsi,4),%edi
                        d: R_X86_64_32S mask
  11:   89 f8                   mov    %edi,%eax
  13:   c3                      retq
% ~/gcc/bin/gcc -v
Using built-in specs.
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc/configure --prefix=/home/odo/gcc --enable-languages=c
--enable-targets=x86_64-unknown-linux-gnu x86_64-unknown-linux-gnu :
(reconfigured) ../gcc/configure --prefix=/home/odo/gcc --enable-languages=c
--without-mudflap --disable-biarch x86_64-unknown-linux-gnu : (reconfigured)
../gcc/configure --prefix=/home/odo/gcc --enable-languages=c --disable-multilib
--disable-biarch x86_64-unknown-linux-gnu
Thread model: posix
gcc version 4.3.0 20061104 (experimental)


-- 
           Summary: result of ffs/clz/ctz/popcount/parity are already sign-
                    extended
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dean at arctic dot org
 GCC build triplet: x86_64-unknown-linux-gnu
  GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: x86_64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29776