s390: Change the handling of S390_ROUND_PER_FPC (which indicates that the
actual rounding mode is to be taken from the FPC register). Previously, this
was just mapped to S390_ROUND_NEAREST_EVEN, which obviously has correctness
issues.
First, we add a function get_bfp_rounding_mode_from_fpc to extract the
rounding mode from the guest FPC when building IR.
Second, have encode_bfp_rounding_mode invoke get_bfp_rounding_mode_from_fpc
whenever a S390_ROUND_PER_FPC is requested.
Third, in insn selection track whether (and if so to what value) the
rounding mode was set for the IRSB at hand. That way redundant assignments
can be avoided. This works well because the IR optimiser do a fine job
recognising end eliminating the expressions returned earlier from
get_bfp_rounding_more_from_fpc. So they get all mapped to the same IRTemp.
Note, VEX r2524 is essential to get this behaviour.
Fourth, remove the rounding more from the bfp_unop/binop/triop s390_insns.
Fifth, if the rounding mode can be set on the insn directly, prefer that
over setting it in the FPC and picking it up from there.
git-svn-id: svn://svn.valgrind.org/vex/trunk@2525 8f6e269a-dfd6-0310-a8e1-e2731360e62c
4 files changed
