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st/glsl_to_tgsi: fix a corner case of std140 layout in uniform buffers

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See the comment in the code for an explanation. This fixes
GL45-CTS.buffer_storage.map_persistent_draw.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
This commit is contained in:
Nicolai Hähnle 2016-10-13 09:54:02 +02:00
parent 57a1514203
commit 9d6f82320c
1 changed files with 28 additions and 1 deletions
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29
src/mesa/state_tracker/st_glsl_to_tgsi.cpp
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@ -2110,8 +2110,35 @@ glsl_to_tgsi_visitor::visit_expression(ir_expression* ir, st_src_reg *op)
cbuf.index = const_offset / 16;
}
else {
ir_expression *offset_expr = ir->operands[1]->as_expression();
st_src_reg offset = op[1];
/* The OpenGL spec is written in such a way that accesses with
* non-constant offset are almost always vec4-aligned. The only
* exception to this are members of structs in arrays of structs:
* each struct in an array of structs is at least vec4-aligned,
* but single-element and [ui]vec2 members of the struct may be at
* an offset that is not a multiple of 16 bytes.
*
* Here, we extract that offset, relying on previous passes to always
* generate offset expressions of the form (+ expr constant_offset).
*
* Note that the std430 layout, which allows more cases of alignment
* less than vec4 in arrays, is not supported for uniform blocks, so
* we do not have to deal with it here.
*/
if (offset_expr && offset_expr->operation == ir_binop_add) {
const_offset_ir = offset_expr->operands[1]->as_constant();
if (const_offset_ir) {
const_offset = const_offset_ir->value.u[0];
cbuf.index = const_offset / 16;
offset_expr->operands[0]->accept(this);
offset = this->result;
}
}
/* Relative/variable index into constant buffer */
emit_asm(ir, TGSI_OPCODE_USHR, st_dst_reg(index_reg), op[1],
emit_asm(ir, TGSI_OPCODE_USHR, st_dst_reg(index_reg), offset,
st_src_reg_for_int(4));
cbuf.reladdr = ralloc(mem_ctx, st_src_reg);
memcpy(cbuf.reladdr, &index_reg, sizeof(index_reg));