Hello,
I discovered a failure relating to atomic NAND operation on x86 platform,
which can be confirmed using the included test-case. The test was done with
gcc 4.2.4, using 8-, 16-, 32- and 64-bit data width. Test cases on other logic
atomic operators passes all width-size except NAND. I have read through the
assembly code generated and confirm that some wrong codes are generated when
no-optimization and -O.
I ) Test case :
/*
Compile using:
gcc -c -march=i686 test.c
To get assembly listing:
gcc -S -march=i686 test.c
To get mix c and assembly listing:
gcc -c -g -Wa,-a,-ad -march=i686 test.c > test-xxx.lst
*/
#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
typedef unsigned char BYTE;
typedef unsigned short WORD;
typedef unsigned long DWORD;
typedef unsigned long long QWORD;
int main(void)
{
WORD xLoc; /* change xLoc type to BYTE, WORD, DWORD, QWORD to test
different data-width */
typeof(xLoc) xIn, xOut, xExpect, i = 1;
xLoc = xIn = (typeof(xIn)) ~ (1<<i);
xExpect = (typeof(xIn)) ~(xIn & ((typeof(xIn)) 0x7F));
/* Both __sync_nand_and_fetch and __sync_fetch_and_nand have the same
problem */
xOut = __sync_nand_and_fetch(&xLoc, (typeof(xIn)) 0x7F);
if (xOut!=xExpect)
printf("__sync_nand_and_fetch():; wrong result; i(%d) xIn(%x)
xExpect(%x) xOut(%x) xLoc(%x)\n",
i, xIn, xExpect, xOut, xLoc);
return 0;
}
II ) Output of gcc -v -save-temps
gcc -o test_bug -v -save-temps -march=i686 test_nand_bug.c
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: ../gcc-4.2.4/configure --prefix=/opt/gcc-4.2.4
--host=i686-pc-linux-gnu --target=i686-pc-linux-gnu
Thread model: posix
gcc version 4.2.4
/opt/gcc-4.2.4/libexec/gcc/i686-pc-linux-gnu/4.2.4/cc1 -E -quiet -v
test_nand_bug.c -march=i686 -fpch-preprocess -o test_nand_bug.i
ignoring nonexistent directory
"/opt/gcc-4.2.4/lib/gcc/i686-pc-linux-gnu/4.2.4/../../../../i686-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/local/include
/opt/gcc-4.2.4/include
/opt/gcc-4.2.4/lib/gcc/i686-pc-linux-gnu/4.2.4/include
/usr/include
End of search list.
/opt/gcc-4.2.4/libexec/gcc/i686-pc-linux-gnu/4.2.4/cc1 -fpreprocessed
test_nand_bug.i -quiet -dumpbase test_nand_bug.c -march=i686 -auxbase
test_nand_bug -version -o test_nand_bug.s
GNU C version 4.2.4 (i686-pc-linux-gnu)
compiled by GNU C version 4.2.4.
GGC heuristics: --param ggc-min-expand=47 --param ggc-min-heapsize=32052
Compiler executable checksum: 383821529167afc2e47a93836e3831a4
as -V -Qy -o test_nand_bug.o test_nand_bug.s
GNU assembler version 2.13.90.0.18 (i386-redhat-linux) using BFD version
2.13.90.0.18 20030206
/opt/gcc-4.2.4/libexec/gcc/i686-pc-linux-gnu/4.2.4/collect2 --eh-frame-hdr -m
elf_i386 -dynamic-linker /lib/ld-linux.so.2 -o test_bug /usr/lib/crt1.o
/usr/lib/crti.o /opt/gcc-4.2.4/lib/gcc/i686-pc-linux-gnu/4.2.4/crtbegin.o
-L/opt/gcc-4.2.4/lib/gcc/i686-pc-linux-gnu/4.2.4
-L/opt/gcc-4.2.4/lib/gcc/i686-pc-linux-gnu/4.2.4/../../.. test_nand_bug.o -lgcc
-lgcc_eh -lc -lgcc -lgcc_eh
/opt/gcc-4.2.4/lib/gcc/i686-pc-linux-gnu/4.2.4/crtend.o /usr/lib/crtn.o
--
Summary: atomic NAND op generate wrong code;
__sync_nand_and_fetch, __sync_fetch_and_nand
Product: gcc
Version: 4.2.4
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: kokseng at ieee dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37908
