target/i386: fix byte swap issue with XMM register access

During the conversion to the gdb_get_reg128 helpers the high and low
parts of the XMM register where inadvertently swapped. This causes
reads of the register to report the incorrect value to gdb.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/971
Fixes: b7b8756 (target/i386: use gdb_get_reg helpers)
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Cc: qemu-stable@nongnu.org
Message-Id: <20220419091020.3008144-25-alex.bennee@linaro.org>

target/i386/gdbstub.c

@@ -129,8 +129,8 @@ int x86_cpu_gdb_read_register(CPUState *cs, GByteArray *mem_buf, int n)
         n -= IDX_XMM_REGS;
         if (n < CPU_NB_REGS32 || TARGET_LONG_BITS == 64) {
             return gdb_get_reg128(mem_buf,
-                                  env->xmm_regs[n].ZMM_Q(0),
-                                  env->xmm_regs[n].ZMM_Q(1));
+                                  env->xmm_regs[n].ZMM_Q(1),
+                                  env->xmm_regs[n].ZMM_Q(0));
         }
     } else {
         switch (n) {