From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60759) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WRmje-0007hR-F2 for qemu-devel@nongnu.org; Sun, 23 Mar 2014 14:03:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WRmjW-0003rS-1G for qemu-devel@nongnu.org; Sun, 23 Mar 2014 14:03:02 -0400 From: Tom Musta Date: Sun, 23 Mar 2014 13:02:48 -0500 Message-Id: <1395597768-3159-1-git-send-email-tommusta@gmail.com> Subject: [Qemu-devel] [PATCH] target-ppc: Bug: VSX Convert to Integer Should Truncate List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Tom Musta , qemu-ppc@nongnu.org The various VSX Convert to Integer instructions should truncate the mantissa. This fix forces the softfloat rounding mode to "round to zero" prior to performing the conversion. After the conversion is completed, the internal rounding mode is restored from the PowerPC FPSCR bits. Signed-off-by: Tom Musta --- This bug was discovered when running wget, which does this: double maxtime; struct timeval tmout; ... tmout.tv_usec = 1000000 * (maxtime - (long) maxtime); The newest PowerPC 64-bit gcc's are now using xscvdpsxds to perform the cast of the double to long. A timeout of 0.95 was erroneously rounding up to 1 and hence computing a negative timeout value. It would be great if we could still get this into 2.0. target-ppc/fpu_helper.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/target-ppc/fpu_helper.c b/target-ppc/fpu_helper.c index e7f3295..ccfc5cc 100644 --- a/target-ppc/fpu_helper.c +++ b/target-ppc/fpu_helper.c @@ -2558,10 +2558,14 @@ void helper_##op(CPUPPCState *env, uint32_t opcode) \ fload_invalid_op_excp(env, POWERPC_EXCP_FP_VXCVI, 0); \ xt.tfld = rnan; \ } else { \ + /* force round to zero mode (truncation) */ \ + set_float_rounding_mode(float_round_to_zero, &env->fp_status); \ xt.tfld = stp##_to_##ttp(xb.sfld, &env->fp_status); \ if (env->fp_status.float_exception_flags & float_flag_invalid) { \ fload_invalid_op_excp(env, POWERPC_EXCP_FP_VXCVI, 0); \ } \ + /* restore rounding mode from FPSCR */ \ + fpscr_set_rounding_mode(env); \ } \ } \ \ -- 1.7.1