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radeonsi/gfx10: fix the vertex order for triangle strips emitted by a GS 

Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
This commit is contained in:
Marek Olšák 2019-11-28 19:46:11 -05:00
parent 91da6a98e7
commit 7730d583c2
1 changed files with 53 additions and 3 deletions
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56
src/gallium/drivers/radeonsi/gfx10_shader_ngg.c
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@ -958,10 +958,28 @@ void gfx10_ngg_gs_emit_vertex(struct si_shader_context *ctx,
const LLVMValueRef iscompleteprim =
LLVMBuildICmp(builder, LLVMIntUGE, curverts, tmp, "");
/* Since the geometry shader emits triangle strips, we need to
* track which primitive is odd and swap vertex indices to get
* the correct vertex order.
*/
LLVMValueRef is_odd = ctx->i1false;
if (stream == 0 && u_vertices_per_prim(sel->gs_output_prim) == 3) {
tmp = LLVMBuildAnd(builder, curverts, ctx->i32_1, "");
is_odd = LLVMBuildICmp(builder, LLVMIntEQ, tmp, ctx->i32_1, "");
}
tmp = LLVMBuildAdd(builder, curverts, ctx->ac.i32_1, "");
LLVMBuildStore(builder, tmp, ctx->gs_curprim_verts[stream]);
/* The per-vertex primitive flag encoding:
* bit 0: whether this vertex finishes a primitive
* bit 1: whether the primitive is odd (if we are emitting triangle strips)
*/
tmp = LLVMBuildZExt(builder, iscompleteprim, ctx->ac.i8, "");
tmp = LLVMBuildOr(builder, tmp,
LLVMBuildShl(builder,
LLVMBuildZExt(builder, is_odd, ctx->ac.i8, ""),
ctx->ac.i8_1, ""), "");
LLVMBuildStore(builder, tmp, ngg_gs_get_emit_primflag_ptr(ctx, vertexptr, stream));
tmp = LLVMBuildLoad(builder, ctx->gs_generated_prims[stream], "");
@ -1206,13 +1224,13 @@ void gfx10_ngg_gs_emit_epilogue(struct si_shader_context *ctx)
tmp = LLVMBuildICmp(builder, LLVMIntULT, tid, num_emit_threads, "");
ac_build_ifcc(&ctx->ac, tmp, 5140);
{
LLVMValueRef flags;
struct ngg_prim prim = {};
prim.num_vertices = verts_per_prim;
tmp = ngg_gs_vertex_ptr(ctx, tid);
tmp = LLVMBuildLoad(builder, ngg_gs_get_emit_primflag_ptr(ctx, tmp, 0), "");
prim.isnull = LLVMBuildICmp(builder, LLVMIntEQ, tmp,
LLVMConstInt(ctx->ac.i8, 0, false), "");
flags = LLVMBuildLoad(builder, ngg_gs_get_emit_primflag_ptr(ctx, tmp, 0), "");
prim.isnull = LLVMBuildNot(builder, LLVMBuildTrunc(builder, flags, ctx->i1, ""), "");
for (unsigned i = 0; i < verts_per_prim; ++i) {
prim.index[i] = LLVMBuildSub(builder, vertlive_scan.result_exclusive,
@ -1220,6 +1238,38 @@ void gfx10_ngg_gs_emit_epilogue(struct si_shader_context *ctx)
prim.edgeflag[i] = ctx->ac.i1false;
}
/* Geometry shaders output triangle strips, but NGG expects triangles.
* We need to change the vertex order for odd triangles to get correct
* front/back facing by swapping 2 vertex indices, but we also have to
* keep the provoking vertex in the same place.
*
* If the first vertex is provoking, swap index 1 and 2.
* If the last vertex is provoking, swap index 0 and 1.
*/
if (verts_per_prim == 3) {
LLVMValueRef is_odd = LLVMBuildLShr(builder, flags, ctx->ac.i8_1, "");
is_odd = LLVMBuildTrunc(builder, is_odd, ctx->i1, "");
LLVMValueRef flatshade_first =
LLVMBuildICmp(builder, LLVMIntEQ,
si_unpack_param(ctx, ctx->vs_state_bits, 4, 2),
ctx->i32_0, "");
struct ngg_prim in = prim;
prim.index[0] = LLVMBuildSelect(builder, flatshade_first,
in.index[0],
LLVMBuildSelect(builder, is_odd,
in.index[1], in.index[0], ""), "");
prim.index[1] = LLVMBuildSelect(builder, flatshade_first,
LLVMBuildSelect(builder, is_odd,
in.index[2], in.index[1], ""),
LLVMBuildSelect(builder, is_odd,
in.index[0], in.index[1], ""), "");
prim.index[2] = LLVMBuildSelect(builder, flatshade_first,
LLVMBuildSelect(builder, is_odd,
in.index[1], in.index[2], ""),
in.index[2], "");
}
build_export_prim(ctx, &prim);
}
ac_build_endif(&ctx->ac, 5140);