static void si_llvm_cube_to_2d_coords(struct lp_build_tgsi_context *bld_base,
LLVMValueRef *in, LLVMValueRef *out)
{
struct gallivm_state *gallivm = bld_base->base.gallivm;
LLVMBuilderRef builder = gallivm->builder;
LLVMTypeRef type = bld_base->base.elem_type;
LLVMValueRef coords[4];
LLVMValueRef mad_args[3];
LLVMValueRef v;
unsigned i;
v = build_cube_intrinsic(gallivm, in);
for (i = 0; i < 4; ++i)
coords[i] = LLVMBuildExtractElement(builder, v,
lp_build_const_int32(gallivm, i), "");
coords[2] = lp_build_intrinsic(builder, "llvm.fabs.f32",
type, &coords[2], 1, LLVMReadNoneAttribute);
coords[2] = lp_build_emit_llvm_unary(bld_base, TGSI_OPCODE_RCP, coords[2]);
mad_args[1] = coords[2];
mad_args[2] = LLVMConstReal(type, 1.5);
mad_args[0] = coords[0];
coords[0] = lp_build_emit_llvm_ternary(bld_base, TGSI_OPCODE_MAD,
mad_args[0], mad_args[1], mad_args[2]);
mad_args[0] = coords[1];
coords[1] = lp_build_emit_llvm_ternary(bld_base, TGSI_OPCODE_MAD,
mad_args[0], mad_args[1], mad_args[2]);
/* apply xyz = yxw swizzle to cooords */
out[0] = coords[1];
out[1] = coords[0];
out[2] = coords[3];
}
void
ac_prepare_cube_coords(struct ac_llvm_context *ctx,
bool is_deriv, bool is_array,
LLVMValueRef *coords_arg,
LLVMValueRef *derivs_arg)
{
LLVMBuilderRef builder = ctx->builder;
struct cube_selection_coords selcoords;
LLVMValueRef coords[3];
LLVMValueRef invma;
build_cube_intrinsic(ctx, coords_arg, &selcoords);
invma = ac_build_intrinsic(ctx, "llvm.fabs.f32",
ctx->f32, &selcoords.ma, 1, AC_FUNC_ATTR_READNONE);
invma = ac_build_fdiv(ctx, LLVMConstReal(ctx->f32, 1.0), invma);
for (int i = 0; i < 2; ++i)
coords[i] = LLVMBuildFMul(builder, selcoords.stc[i], invma, "");
coords[2] = selcoords.id;
if (is_deriv && derivs_arg) {
LLVMValueRef derivs[4];
int axis;
/* Convert cube derivatives to 2D derivatives. */
for (axis = 0; axis < 2; axis++) {
LLVMValueRef deriv_st[2];
LLVMValueRef deriv_ma;
/* Transform the derivative alongside the texture
* coordinate. Mathematically, the correct formula is
* as follows. Assume we're projecting onto the +Z face
* and denote by dx/dh the derivative of the (original)
* X texture coordinate with respect to horizontal
* window coordinates. The projection onto the +Z face
* plane is:
*
* f(x,z) = x/z
*
* Then df/dh = df/dx * dx/dh + df/dz * dz/dh
* = 1/z * dx/dh - x/z * 1/z * dz/dh.
*
* This motivatives the implementation below.
*
* Whether this actually gives the expected results for
* apps that might feed in derivatives obtained via
* finite differences is anyone's guess. The OpenGL spec
* seems awfully quiet about how textureGrad for cube
* maps should be handled.
*/
build_cube_select(builder, &selcoords, &derivs_arg[axis * 3],
deriv_st, &deriv_ma);
deriv_ma = LLVMBuildFMul(builder, deriv_ma, invma, "");
for (int i = 0; i < 2; ++i)
derivs[axis * 2 + i] =
LLVMBuildFSub(builder,
LLVMBuildFMul(builder, deriv_st[i], invma, ""),
LLVMBuildFMul(builder, deriv_ma, coords[i], ""), "");
}
memcpy(derivs_arg, derivs, sizeof(derivs));
}
/* Shift the texture coordinate. This must be applied after the
* derivative calculation.
*/
for (int i = 0; i < 2; ++i)
coords[i] = LLVMBuildFAdd(builder, coords[i], LLVMConstReal(ctx->f32, 1.5), "");
if (is_array) {
/* for cube arrays coord.z = coord.w(array_index) * 8 + face */
/* coords_arg.w component - array_index for cube arrays */
LLVMValueRef tmp = LLVMBuildFMul(ctx->builder, coords_arg[3], LLVMConstReal(ctx->f32, 8.0), "");
coords[2] = LLVMBuildFAdd(ctx->builder, tmp, coords[2], "");
}
memcpy(coords_arg, coords, sizeof(coords));
}
