On 10/22/18 10:34 AM, Matt Turner wrote: > On Fri, Oct 5, 2018 at 11:15 AM Sagar Ghuge <sagar.gh...@intel.com> wrote: >> >> avoid misinterpretation of encoded immediate values in instruction and >> disassembled output. >> >> Signed-off-by: Sagar Ghuge <sagar.gh...@intel.com> >> --- >> While encoding the immediate floating point values in instruction we use >> values upto precision 8, but while disassembling, we print precision to >> 6 places, which round up the value and gives wrong interpretation for >> encoded immediate constant. Printing it upto precision 8 will help in >> reassembling it again. > > Let's put that in the commit message. > >> src/intel/compiler/brw_disasm.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/src/intel/compiler/brw_disasm.c >> b/src/intel/compiler/brw_disasm.c >> index 322f4544df..7cbbc080b3 100644 >> --- a/src/intel/compiler/brw_disasm.c >> +++ b/src/intel/compiler/brw_disasm.c >> @@ -1293,7 +1293,7 @@ imm(FILE *file, const struct gen_device_info *devinfo, >> enum brw_reg_type type, >> format(file, "0x%08xV", brw_inst_imm_ud(devinfo, inst)); >> break; >> case BRW_REGISTER_TYPE_F: >> - format(file, "%-gF", brw_inst_imm_f(devinfo, inst)); >> + format(file, "%.8fF", brw_inst_imm_f(devinfo, inst)); > > I'm not sure 8 digits is sufficient to get an exact representation > that the assembler can "round-trip". This page [1] indicates that 9 > digits are necessary for binary->decimal->binary round-trips. > I was also not sure about it, [1] article is nice. > NIR takes another approach: > > vec1 32 ssa_0 = load_const (0x3f800000 /* 1.000000 */) > > What do you think about printing the binary representation and the > floating-point value? That way humans can easily read one number and > the assembler can easily read the other :) > I think we can just print F and DF to 9 and 17 precision respectively to avoid output alignment issue.
> Also, I think the DF case immediately after this should be handled as well. > Yes, I was planning to handle it when I shift to 64 bit datatypes. But I can club both in single patch. > [1] > https://www.exploringbinary.com/number-of-digits-required-for-round-trip-conversions/ > _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev