add gitlab issues in toml format

1 files changed, 103 insertions, 0 deletions

diff --git a/gitlab/issues/target_s390x/host_missing/accel_TCG/618.toml b/gitlab/issues/target_s390x/host_missing/accel_TCG/618.toml
new file mode 100644
index 00000000..cd397f72
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+++ b/gitlab/issues/target_s390x/host_missing/accel_TCG/618.toml
@@ -0,0 +1,103 @@
+id = 618
+title = "overflow condition code determined incorrectly after subtraction on s390x"
+state = "closed"
+created_at = "2021-09-12T22:42:18.749Z"
+closed_at = "2022-04-02T17:38:46.614Z"
+labels = ["accel: TCG", "kind::Bug", "target: s390x", "workflow::Confirmed"]
+url = "https://gitlab.com/qemu-project/qemu/-/issues/618"
+host-os = "Ubuntu 20.04"
+host-arch = "x86_64"
+qemu-version = "6.1.0"
+guest-os = "Linux"
+guest-arch = "s390x"
+description = """Paul Eggert found this bug, just by taking a look at the file `qemu/target/s390x/tcg/cc_helper.c`.
+
+The following program
+[foo.c](/uploads/c1f425684fd661c4437950d7d8ddf31d/foo.c)
+```
+#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));
+  }
+}
+```
+should print
+```
+a = 0x0, b = 0x80000000
+no_overflow = 0
+a = 0x0, 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 = 0x0, b = 0x80000000
+no_overflow = 1
+a = 0x0, 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 = 0x0, b = 0x80000000
+no_overflow = 1
+a = 0x0, 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
+        sgr     %r1,%r3    ;; subtract b from a
+        bnor    %r14       ;; if no overflow, return %r2 = 0
+        lghi    %r2,1
+        br      %r14       ;; otherwise, return %r2 = 1
+```
+
+The condition code and the overflow bit are defined in the z/Architecture Principles of Operation (POP) http://publibfi.boulder.ibm.com/epubs/pdf/dz9zr011.pdf page 7-5 / 7-6 / 7-388 : "In mathematical terms, signed addition and subtraction produce a fixed-point overflow when the result is outside the range of representation for signed binary integers."
+
+I conclude that the bug is in QEMU: QEMU does not set the overflow condition code correctly."""
+reproduce = """[foo.static.s390x](/uploads/e4b79b019db590f3a4b13cac41e57ba6/foo.static.s390x)
+(the result of "s390x-linux-gnu-gcc-10 -static -O2 foo.c -o foo.static.s390x")
+
+1. `qemu-s390x foo.static.s390x`"""
+additional = """The attached patch fixes it.
+[0002-s390x-Fix-determination-of-overflow-condition-code-a.patch](/uploads/8d414f84fe0ed36bf07bd28f5e7836ab/0002-s390x-Fix-determination-of-overflow-condition-code-a.patch)"""