[Mesa-dev] [Mesa-stable] [PATCH] radeonsi: add a workaround for bitfield_extract when count is 0

[Marek Olšák]

Since LLVM 7.0 has already been released:

Reviewed-by: Marek Olšák <marek.olsak at amd.com>

Marek
On Tue, Sep 25, 2018 at 12:46 AM Timothy Arceri <tarceri at itsqueeze.com> wrote:
>
> On 25/9/18 10:35 am, Marek Olšák wrote:
> > Do you know what's broken in LLVM? Or is it a problem with the ISA?
>
> I haven't actually dug any further. Adding Samuel to see if he remembers
> more.
>
> However according to the original bug report this is a regression when
> going from LLVM 6 to LLVM 7. I see the issue on both polaris and vega.
>
> >
> > Marek
> >
> > On Fri, Sep 21, 2018 at 10:38 PM, Timothy Arceri <tarceri at itsqueeze.com> wrote:
> >> This ports the fix from 3d41757788ac. Both LLVM 7 & 8 continue
> >> to have this problem.
> >>
> >> It fixes rendering issues in some menu and loading screens of
> >> Civ VI which can be seen in the trace from bug 104602.
> >>
> >> Note: This does not fix the black triangles on Vega for bug
> >> 104602.
> >>
> >> Cc: mesa-stable at lists.freedesktop.org
> >> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104602
> >> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107276
> >> ---
> >>   .../drivers/radeonsi/si_shader_tgsi_alu.c     | 41 ++++++++++++++-----
> >>   1 file changed, 30 insertions(+), 11 deletions(-)
> >>
> >> diff --git a/src/gallium/drivers/radeonsi/si_shader_tgsi_alu.c b/src/gallium/drivers/radeonsi/si_shader_tgsi_alu.c
> >> index f54d025aec0..814362bc963 100644
> >> --- a/src/gallium/drivers/radeonsi/si_shader_tgsi_alu.c
> >> +++ b/src/gallium/drivers/radeonsi/si_shader_tgsi_alu.c
> >> @@ -494,18 +494,37 @@ static void emit_bfe(const struct lp_build_tgsi_action *action,
> >>                       struct lp_build_emit_data *emit_data)
> >>   {
> >>          struct si_shader_context *ctx = si_shader_context(bld_base);
> >> -       LLVMValueRef bfe_sm5;
> >> -       LLVMValueRef cond;
> >> -
> >> -       bfe_sm5 = ac_build_bfe(&ctx->ac, emit_data->args[0],
> >> -                              emit_data->args[1], emit_data->args[2],
> >> -                              emit_data->info->opcode == TGSI_OPCODE_IBFE);
> >>
> >> -       /* Correct for GLSL semantics. */
> >> -       cond = LLVMBuildICmp(ctx->ac.builder, LLVMIntUGE, emit_data->args[2],
> >> -                            LLVMConstInt(ctx->i32, 32, 0), "");
> >> -       emit_data->output[emit_data->chan] =
> >> -               LLVMBuildSelect(ctx->ac.builder, cond, emit_data->args[0], bfe_sm5, "");
> >> +       if (HAVE_LLVM < 0x0700) {
> >> +               LLVMValueRef bfe_sm5 =
> >> +                       ac_build_bfe(&ctx->ac, emit_data->args[0],
> >> +                                    emit_data->args[1], emit_data->args[2],
> >> +                                    emit_data->info->opcode == TGSI_OPCODE_IBFE);
> >> +
> >> +               /* Correct for GLSL semantics. */
> >> +               LLVMValueRef cond = LLVMBuildICmp(ctx->ac.builder, LLVMIntUGE, emit_data->args[2],
> >> +                                                 LLVMConstInt(ctx->i32, 32, 0), "");
> >> +               emit_data->output[emit_data->chan] =
> >> +                       LLVMBuildSelect(ctx->ac.builder, cond, emit_data->args[0], bfe_sm5, "");
> >> +       } else {
> >> +               /* FIXME: LLVM 7 returns incorrect result when count is 0.
> >> +                * https://bugs.freedesktop.org/show_bug.cgi?id=107276
> >> +                */
> >> +               LLVMValueRef zero = ctx->i32_0;
> >> +               LLVMValueRef bfe_sm5 =
> >> +                       ac_build_bfe(&ctx->ac, emit_data->args[0],
> >> +                                    emit_data->args[1], emit_data->args[2],
> >> +                                    emit_data->info->opcode == TGSI_OPCODE_IBFE);
> >> +
> >> +               /* Correct for GLSL semantics. */
> >> +               LLVMValueRef cond = LLVMBuildICmp(ctx->ac.builder, LLVMIntUGE, emit_data->args[2],
> >> +                                                 LLVMConstInt(ctx->i32, 32, 0), "");
> >> +               LLVMValueRef cond2 = LLVMBuildICmp(ctx->ac.builder, LLVMIntEQ, emit_data->args[2],
> >> +                                                  zero, "");
> >> +               bfe_sm5 = LLVMBuildSelect(ctx->ac.builder, cond, emit_data->args[0], bfe_sm5, "");
> >> +               emit_data->output[emit_data->chan] =
> >> +                       LLVMBuildSelect(ctx->ac.builder, cond2, zero, bfe_sm5, "");
> >> +       }
> >>   }
> >>
> >>   /* this is ffs in C */
> >> --
> >> 2.17.1
> >>
> >> _______________________________________________
> >> mesa-stable mailing list
> >> mesa-stable at lists.freedesktop.org
> >> https://lists.freedesktop.org/mailman/listinfo/mesa-stable