diff options
| author | Bruno Haible <bruno@clisp.org> | 2022-03-23 17:26:21 +0100 |
|---|---|---|
| committer | Thomas Huth <thuth@redhat.com> | 2022-04-01 13:06:07 +0200 |
| commit | fc6e0d0f2db5126592bb4066d484fcdfc14ccf36 (patch) | |
| tree | ee1c652c9bdafc5362acde237186121bcdc17764 /target/s390x | |
| parent | 5a2e67a691501bc4dd81c46c81b8f1881c8bd5df (diff) | |
target/s390x: Fix determination of overflow condition code after subtraction
Reported by Paul Eggert in
https://lists.gnu.org/archive/html/bug-gnulib/2021-09/msg00050.html
This program currently prints different results when run with TCG instead
of running on real s390x hardware:
#include <stdio.h>
int overflow_32 (int x, int y)
{
int sum;
return __builtin_sub_overflow (x, y, &sum);
}
int overflow_64 (long long x, long long y)
{
long sum;
return __builtin_sub_overflow (x, y, &sum);
}
int a1 = 0;
int b1 = -2147483648;
long long a2 = 0L;
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));
}
}
Signed-off-by: Bruno Haible <bruno@clisp.org>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/618
Message-Id: <20220323162621.139313-3-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Diffstat (limited to 'target/s390x')
| -rw-r--r-- | target/s390x/tcg/cc_helper.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/target/s390x/tcg/cc_helper.c b/target/s390x/tcg/cc_helper.c index e11cdb745d..b2e8d3d9f5 100644 --- a/target/s390x/tcg/cc_helper.c +++ b/target/s390x/tcg/cc_helper.c @@ -151,7 +151,7 @@ static uint32_t cc_calc_add_64(int64_t a1, int64_t a2, int64_t ar) static uint32_t cc_calc_sub_64(int64_t a1, int64_t a2, int64_t ar) { - if ((a1 > 0 && a2 < 0 && ar < 0) || (a1 < 0 && a2 > 0 && ar > 0)) { + if ((a1 >= 0 && a2 < 0 && ar < 0) || (a1 < 0 && a2 > 0 && ar > 0)) { return 3; /* overflow */ } else { if (ar < 0) { @@ -211,7 +211,7 @@ static uint32_t cc_calc_add_32(int32_t a1, int32_t a2, int32_t ar) static uint32_t cc_calc_sub_32(int32_t a1, int32_t a2, int32_t ar) { - if ((a1 > 0 && a2 < 0 && ar < 0) || (a1 < 0 && a2 > 0 && ar > 0)) { + if ((a1 >= 0 && a2 < 0 && ar < 0) || (a1 < 0 && a2 > 0 && ar > 0)) { return 3; /* overflow */ } else { if (ar < 0) { |