The dh_alias redirect is intended to handle TCG types as distinguished
from C types. TCG does not distinguish signed int from unsigned int,
because they are the same size. However, we need to retain this
distinction for dh_typecode, lest we fail to extend abi types properly
for the host call parameters.
This bug was detected when running the 'arm' emulator on an s390
system. The s390 uses TCG_TARGET_EXTEND_ARGS which triggers code
in tcg_gen_callN to extend 32 bit values to 64 bits; the incorrect
sign data in the typemask for each argument caused the values to be
extended as unsigned values.
This simple program exhibits the problem:
static volatile int num = -9;
static volatile int den = -5;
int main(void)
{
int quo = num / den;
printf("num %d den %d quo %d\n", num, den, quo);
exit(0);
}
When run on the broken qemu, this results in:
num -9 den -5 quo 0
The correct result is:
num -9 den -5 quo 1
Fixes: 7319d83a73 ("tcg: Combine dh_is_64bit and dh_is_signed to dh_typecode")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/876
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reported-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
Tested-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
Tested-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
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