diff options
Diffstat (limited to 'results/classifier/zero-shot-user-mode/output/instruction/616')
| -rw-r--r-- | results/classifier/zero-shot-user-mode/output/instruction/616 | 113 |
1 files changed, 0 insertions, 113 deletions
diff --git a/results/classifier/zero-shot-user-mode/output/instruction/616 b/results/classifier/zero-shot-user-mode/output/instruction/616 deleted file mode 100644 index e4682eac6..000000000 --- a/results/classifier/zero-shot-user-mode/output/instruction/616 +++ /dev/null @@ -1,113 +0,0 @@ -instruction: 0.412 -syscall: 0.320 -runtime: 0.268 - - - -overflow condition code determined incorrectly after addition on s390x -Description of problem: -The following program foo.c -[foo.c](/uploads/78f5f799af6e3c400a6a42634f3f0e63/foo.c) - -``` -#include <stdio.h> - -int overflow_32 (int x, int y) -{ - int sum; - return ! __builtin_add_overflow (x, y, &sum); -} - -int overflow_64 (long long x, long long y) -{ - long sum; - return ! __builtin_add_overflow (x, y, &sum); -} - -int a1 = -2147483648; -int b1 = -2147483648; -long long a2 = -9223372036854775808L; -long long b2 = -9223372036854775808L; - -int main () -{ - { - int a = a1; - int b = b1; - printf ("a = 0x%x, b = 0x%x\n", a, b); - printf ("no_overflow = %d\n", overflow_32 (a, b)); - } - { - long long a = a2; - long long b = b2; - printf ("a = 0x%llx, b = 0x%llx\n", a, b); - printf ("no_overflow = %d\n", overflow_64 (a, b)); - } -} -``` - -should print - -``` -a = 0x80000000, b = 0x80000000 -no_overflow = 0 -a = 0x8000000000000000, b = 0x8000000000000000 -no_overflow = 0 -``` - -However, when compiled as an s390x program and executed through -qemu 6.1.0 (Linux user-mode), it prints 'no_overflow = 1' twice. - -``` -$ s390x-linux-gnu-gcc-10 --version -s390x-linux-gnu-gcc-10 (Ubuntu 10.3.0-1ubuntu1~20.04) 10.3.0 -``` - -``` -$ s390x-linux-gnu-gcc-10 -static foo.c -$ ~/inst-qemu/6.1.0/bin/qemu-s390x a.out -a = 0x80000000, b = 0x80000000 -no_overflow = 1 -a = 0x8000000000000000, b = 0x8000000000000000 -no_overflow = 1 -``` - -``` -$ s390x-linux-gnu-gcc-10 -O2 -static foo.c -$ ~/inst-qemu/6.1.0/bin/qemu-s390x a.out -a = 0x80000000, b = 0x80000000 -no_overflow = 1 -a = 0x8000000000000000, b = 0x8000000000000000 -no_overflow = 1 -``` - -The code generated by 's390x-linux-gnu-gcc-10 -O2' makes use of the -'o' (overflow / ones) condition code: - -``` -overflow_64: - lgr %r1,%r2 ;; copy a into %r1 - lghi %r2,0 - agr %r1,%r3 ;; add a and b - bnor %r14 ;; if no overflow, return %r2 = 0 - lghi %r2,1 - br %r14 ;; otherwise, return %r2 = 1 -``` - -Either the bug is in GCC, that is, GCC produces code that uses the CPU's -overflow condition code when it shouldn't. - -Or the bug is in QEMU, that is, QEMU does not set the overflow condition -code correctly. - -This can be decided by running the above program on real Linux/s390x hardware -(to which I don't have access). -Steps to reproduce: -[foo.static.s390x](/uploads/ac41abf4c54baf9ca96ba82d75a24ad6/foo.static.s390x) -(foo.static.s390x is attached, the result of "s390x-linux-gnu-gcc-10 -static -O2 foo.c -o foo.static.s390x") - -1. `qemu-s390x foo.static.s390x` -Additional information: -If the bug is really in QEMU, the attached patch fixes it. - -[0001-s390x-Fix-determination-of-overflow-condition-code-a.patch](/uploads/552917079ccd25f1861d682fc9dee3e8/0001-s390x-Fix-determination-of-overflow-condition-code-a.patch) |