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radv/llvm: implement a workaround for gl_FragCoord.z with VRS on GFX10.3

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Without it, FragCoord.z will have the value of one of the fine pixels
instead of the center of the coarse pixel.

It's only enabled for RADV.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7837>
This commit is contained in:
Samuel Pitoiset 2020-12-11 08:46:19 +01:00 • committed by Marge Bot
parent 7a464f4296
commit 45524afe95
4 changed files with 40 additions and 7 deletions
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40
src/amd/llvm/ac_nir_to_llvm.c
View file

@ -3328,6 +3328,37 @@ emit_load_frag_shading_rate(struct ac_nir_context *ctx)
return LLVMBuildOr(ctx->ac.builder, x_rate, y_rate, "");
}
static LLVMValueRef
emit_load_frag_coord(struct ac_nir_context *ctx)
{
LLVMValueRef values[4] = {
ac_get_arg(&ctx->ac, ctx->args->frag_pos[0]), ac_get_arg(&ctx->ac, ctx->args->frag_pos[1]),
ac_get_arg(&ctx->ac, ctx->args->frag_pos[2]),
ac_build_fdiv(&ctx->ac, ctx->ac.f32_1, ac_get_arg(&ctx->ac, ctx->args->frag_pos[3]))};
if (ctx->abi->adjust_frag_coord_z) {
/* Adjust gl_FragCoord.z for VRS due to a hw bug on some GFX10.3 chips. */
LLVMValueRef frag_z = values[2];
/* dFdx fine */
LLVMValueRef adjusted_frag_z = emit_ddxy(ctx, nir_op_fddx_fine, frag_z);
/* adjusted_frag_z * 0.0625 + frag_z */
adjusted_frag_z = LLVMBuildFAdd(ctx->ac.builder, frag_z,
LLVMBuildFMul(ctx->ac.builder, adjusted_frag_z,
LLVMConstReal(ctx->ac.f32, 0.0625), ""), "");
/* VRS Rate X = Ancillary[2:3] */
LLVMValueRef x_rate = ac_unpack_param(&ctx->ac, ac_get_arg(&ctx->ac, ctx->args->ancillary), 2, 2);
/* xRate = xRate == 0x1 ? adjusted_frag_z : frag_z. */
LLVMValueRef cond = LLVMBuildICmp(ctx->ac.builder, LLVMIntEQ, x_rate, ctx->ac.i32_1, "");
values[2] = LLVMBuildSelect(ctx->ac.builder, cond, adjusted_frag_z, frag_z, "");
}
return ac_to_integer(&ctx->ac, ac_build_gather_values(&ctx->ac, values, 4));
}
static void visit_intrinsic(struct ac_nir_context *ctx, nir_intrinsic_instr *instr)
{
LLVMValueRef result = NULL;
@ -3421,14 +3452,9 @@ static void visit_intrinsic(struct ac_nir_context *ctx, nir_intrinsic_instr *ins
case nir_intrinsic_load_sample_mask_in:
result = ctx->abi->load_sample_mask_in(ctx->abi);
break;
case nir_intrinsic_load_frag_coord: {
LLVMValueRef values[4] = {
ac_get_arg(&ctx->ac, ctx->args->frag_pos[0]), ac_get_arg(&ctx->ac, ctx->args->frag_pos[1]),
ac_get_arg(&ctx->ac, ctx->args->frag_pos[2]),
ac_build_fdiv(&ctx->ac, ctx->ac.f32_1, ac_get_arg(&ctx->ac, ctx->args->frag_pos[3]))};
result = ac_to_integer(&ctx->ac, ac_build_gather_values(&ctx->ac, values, 4));
case nir_intrinsic_load_frag_coord:
result = emit_load_frag_coord(ctx);
break;
}
case nir_intrinsic_load_frag_shading_rate:
result = emit_load_frag_shading_rate(ctx);
break;

5
src/amd/llvm/ac_shader_abi.h
View file

@ -165,6 +165,11 @@ struct ac_shader_abi {
/* Clamp div by 0 (so it won't produce NaN) */
bool clamp_div_by_zero;
/* Whether gl_FragCoord.z should be adjusted for VRS due to a hw bug on
* some GFX10.3 chips.
*/
bool adjust_frag_coord_z;
};
#endif /* AC_SHADER_ABI_H */

1
src/amd/vulkan/radv_nir_to_llvm.c
View file

@ -3896,6 +3896,7 @@ LLVMModuleRef ac_translate_nir_to_llvm(struct ac_llvm_compiler *ac_llvm,
ctx.abi.load_sampler_desc = radv_get_sampler_desc;
ctx.abi.load_resource = radv_load_resource;
ctx.abi.clamp_shadow_reference = false;
ctx.abi.adjust_frag_coord_z = args->options->adjust_frag_coord_z;
ctx.abi.robust_buffer_access = args->options->robust_buffer_access;
bool is_ngg = is_pre_gs_stage(shaders[0]->info.stage) && args->options->key.vs_common_out.as_ngg;

1
src/gallium/drivers/radeonsi/si_shader_llvm.c
View file

@ -487,6 +487,7 @@ static bool si_nir_build_llvm(struct si_shader_context *ctx, struct nir_shader *
ctx->abi.robust_buffer_access = true;
ctx->abi.convert_undef_to_zero = true;
ctx->abi.clamp_div_by_zero = ctx->screen->options.clamp_div_by_zero;
ctx->abi.adjust_frag_coord_z = false;
const struct si_shader_info *info = &ctx->shader->selector->info;
for (unsigned i = 0; i < info->num_outputs; i++) {