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| author | Christian Krinitsin <mail@krinitsin.com> | 2025-05-30 16:52:07 +0200 |
|---|---|---|
| committer | Christian Krinitsin <mail@krinitsin.com> | 2025-05-30 16:52:17 +0200 |
| commit | 9260319e7411ff8281700a532caa436f40120ec4 (patch) | |
| tree | 2f6bfe5f3458dd49d328d3a9eb508595450adec0 /gitlab/issues/target_i386/host_missing/accel_missing/2817.toml | |
| parent | 225caa38269323af1bfc2daadff5ec8bd930747f (diff) | |
| download | emulator-bug-study-9260319e7411ff8281700a532caa436f40120ec4.tar.gz emulator-bug-study-9260319e7411ff8281700a532caa436f40120ec4.zip | |
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Diffstat (limited to 'gitlab/issues/target_i386/host_missing/accel_missing/2817.toml')
| -rw-r--r-- | gitlab/issues/target_i386/host_missing/accel_missing/2817.toml | 63 |
1 files changed, 0 insertions, 63 deletions
diff --git a/gitlab/issues/target_i386/host_missing/accel_missing/2817.toml b/gitlab/issues/target_i386/host_missing/accel_missing/2817.toml deleted file mode 100644 index aa1af6f2..00000000 --- a/gitlab/issues/target_i386/host_missing/accel_missing/2817.toml +++ /dev/null @@ -1,63 +0,0 @@ -id = 2817 -title = "Strange floating-point behaviour under Windows with some CPU models" -state = "opened" -created_at = "2025-02-18T12:02:17.591Z" -closed_at = "n/a" -labels = ["Softfloat", "target: i386"] -url = "https://gitlab.com/qemu-project/qemu/-/issues/2817" -host-os = "Debian 12" -host-arch = "x86_64" -qemu-version = "QEMU emulator version 7.2.13 (Debian 1:7.2+dfsg-7+deb12u7)" -guest-os = "Windows 10, Windows Server 2022" -guest-arch = "x86_64" -description = """I'm encountering a very weird bug with some floating-point maths code, but only under very specific configurations. First I thought it was a Clang bug, but then further digging eventually showed it to only occur under Windows VMs with specific QEMU CPU options, I'm not certain whether it is a QEMU/KVM bug or a Windows bug, but thought starting here would be easiest. - -When compiled under MSVC Clang with modern CPU instructions disabled (e.g. `-march=pentium3` or `-march=pentium-mmx`), the `floorf()` call in the following program always returns 0.0, while the truncation works correctly: - -``` -#include <math.h> -#include <stdio.h> -#include <stdlib.h> - -int main(int argc, char **argv) -{ -\tfloat n = atof(argv[1]); -\tprintf("n = %f\\n", n); -\t -\tfloat f = floorf(n); -\tprintf("f = %f\\n", f); -\t -\tfloat c = (int)(n); -\tprintf("c = %f\\n", c); -\t -\treturn 0; -} -``` - -Example output on an affected VM: - -``` -C:\\Users\\Administrator> floorf-p3.exe 10 -n = 10.000000 -f = 0.000000 -c = 10.000000 - -C:\\Users\\Administrator> floorf-p4.exe 10 -n = 10.000000 -f = 10.000000 -c = 10.000000 -``` - -(`floorf-p3.exe` was compiled with `-march=pentium3` and `floorf-p4.exe` with `-march=pentium4` above) - -I've tried a few QEMU CPU models on a variety of Intel/AMD VM hosts and two different Windows versions (10 and Server 2022), and observed the following: - -* `host-passthrough` - works (on AMD and Intel hosts) -* `qemu64` - broken -* `EPYC-Milan` - works -* `Westmere` - works -* `Penryn` - broken - -(I also reported this via the mailing list, but I think it might've swallowed my post)""" -reproduce = "n/a" -additional = "n/a" |