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Diffstat (limited to 'gitlab/issues/target_arm/host_missing/accel_TCG/1612.toml')
| -rw-r--r-- | gitlab/issues/target_arm/host_missing/accel_TCG/1612.toml | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/gitlab/issues/target_arm/host_missing/accel_TCG/1612.toml b/gitlab/issues/target_arm/host_missing/accel_TCG/1612.toml new file mode 100644 index 000000000..cb03a7d01 --- /dev/null +++ b/gitlab/issues/target_arm/host_missing/accel_TCG/1612.toml @@ -0,0 +1,59 @@ +id = 1612 +title = "SVE first-faulting gather loads return incorrect data" +state = "closed" +created_at = "2023-04-21T16:12:04.887Z" +closed_at = "2023-05-18T14:51:26.696Z" +labels = ["Closed::Fixed", "accel: TCG", "target: arm"] +url = "https://gitlab.com/qemu-project/qemu/-/issues/1612" +host-os = "Ubuntu 20.04 LTS" +host-arch = "x86_64" +qemu-version = "qemu-aarch64 version 5.0.50 (v5.0.0-403-g50de9b78ce-dirty) (and latest master)" +guest-os = "n/a" +guest-arch = "n/a" +description = """The results of `ldff1(b|h|w|d)` seem to be incorrect when `<Zt> == <Zm>`. The first element is duplicated throughout the vector while the FFR indicates that all elements were successfully loaded. This happens since https://gitlab.com/qemu-project/qemu/-/commit/50de9b78cec06e6d16e92a114a505779359ca532, and still happens on the latest master.""" +reproduce = """1. This assembly sequence loads data with an `ldff1d` instruction (and also loads the ffr). Note that with `ldff1d`, `<Zt> == <Zm>`. + +asmtest.s +``` + .type asmtest, @function + .balign 16 + .global asmtest +asmtest: + setffr + ptrue p0.d + index z1.d, #0, #1 + ldff1d z1.d, p0/z, [x0, z1.d, LSL #3] + rdffr p1.b + st1d {z1.d}, p0, [x1] + str p1, [x2] + ret +``` + +This harness for convenience intialises some data and checks the element at index 1, which should be 1. + +test.c +``` +#include <arm_sve.h> +#include <stdio.h> + +void asmtest(int64_t const * data, svint64_t * loaded, svbool_t * ffr); + +int main() { + const int64_t data[] = {42, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, + 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, + 22, 23, 24, 25, 26, 27, 28, 29, 30, 31}; + svint64_t loaded; + svbool_t ffr; + + asmtest(data, &loaded, &ffr); + + // Check value of element at index 1 + svuint64_t lanes = svindex_u64(0, 1); + svbool_t lane = svcmpeq_n_u64(svptrue_b64(), lanes, 1); + printf("%ld\\n", svaddv_s64(lane, loaded)); +} +``` + +2. ```clang-15 -fuse-ld=lld -march=armv8-a+sve2 -target aarch64-unknown-linux-gnu -static *.c *.s -o svldffgathertest``` +3. ```qemu-aarch64 svldffgathertest``` - the value printed should be 1, but it can be seen that all values in the loaded vector are 42.""" +additional = """The above code was successfully tested on real SVE hardware. Normal gathers work fine in QEMU, as does a non-gather first-fault load.""" |