/*
* Copyright © 2010 Intel Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
/**
* \file lower_instructions.cpp
*
* Many GPUs lack native instructions for certain expression operations, and
* must replace them with some other expression tree. This pass lowers some
* of the most common cases, allowing the lowering code to be implemented once
* rather than in each driver backend.
*
* Currently supported transformations:
* - SUB_TO_ADD_NEG
* - DIV_TO_MUL_RCP
* - INT_DIV_TO_MUL_RCP
* - EXP_TO_EXP2
* - POW_TO_EXP2
* - LOG_TO_LOG2
* - MOD_TO_FRACT
* - LRP_TO_ARITH
* - BITFIELD_INSERT_TO_BFM_BFI
*
* SUB_TO_ADD_NEG:
* ---------------
* Breaks an ir_binop_sub expression down to add(op0, neg(op1))
*
* This simplifies expression reassociation, and for many backends
* there is no subtract operation separate from adding the negation.
* For backends with native subtract operations, they will probably
* want to recognize add(op0, neg(op1)) or the other way around to
* produce a subtract anyway.
*
* DIV_TO_MUL_RCP and INT_DIV_TO_MUL_RCP:
* --------------------------------------
* Breaks an ir_binop_div expression down to op0 * (rcp(op1)).
*
* Many GPUs don't have a divide instruction (945 and 965 included),
* but they do have an RCP instruction to compute an approximate
* reciprocal. By breaking the operation down, constant reciprocals
* can get constant folded.
*
* DIV_TO_MUL_RCP only lowers floating point division; INT_DIV_TO_MUL_RCP
* handles the integer case, converting to and from floating point so that
* RCP is possible.
*
* EXP_TO_EXP2 and LOG_TO_LOG2:
* ----------------------------
* Many GPUs don't have a base e log or exponent instruction, but they
* do have base 2 versions, so this pass converts exp and log to exp2
* and log2 operations.
*
* POW_TO_EXP2:
* -----------
* Many older GPUs don't have an x**y instruction. For these GPUs, convert
* x**y to 2**(y * log2(x)).
*
* MOD_TO_FRACT:
* -------------
* Breaks an ir_binop_mod expression down to (op1 * fract(op0 / op1))
*
* Many GPUs don't have a MOD instruction (945 and 965 included), and
* if we have to break it down like this anyway, it gives an
* opportunity to do things like constant fold the (1.0 / op1) easily.
*
* LRP_TO_ARITH:
* -------------
* Converts ir_triop_lrp to (op0 * (1.0f - op2)) + (op1 * op2).
*
* BITFIELD_INSERT_TO_BFM_BFI:
* ---------------------------
* Breaks ir_quadop_bitfield_insert into ir_binop_bfm (bitfield mask) and
* ir_triop_bfi (bitfield insert).
*
* Many GPUs implement the bitfieldInsert() built-in from ARB_gpu_shader_5
* with a pair of instructions.
*
*/
#include "main/core.h" /* for M_LOG2E */
#include "glsl_types.h"
#include "ir.h"
#include "ir_builder.h"
#include "ir_optimization.h"
using namespace ir_builder;
class lower_instructions_visitor : public ir_hierarchical_visitor {
public:
lower_instructions_visitor(unsigned lower)
: progress(false), lower(lower) { }
ir_visitor_status visit_leave(ir_expression *);
bool progress;
private:
unsigned lower; /** Bitfield of which operations to lower */
void sub_to_add_neg(ir_expression *);
void div_to_mul_rcp(ir_expression *);
void int_div_to_mul_rcp(ir_expression *);
void mod_to_fract(ir_expression *);
void exp_to_exp2(ir_expression *);
void pow_to_exp2(ir_expression *);
void log_to_log2(ir_expression *);
void lrp_to_arith(ir_expression *);
void bitfield_insert_to_bfm_bfi(ir_expression *);
};
/**
* Determine if a particular type of lowering should occur
*/
#define lowering(x) (this->lower & x)
bool
lower_instructions(exec_list *instructions, unsigned what_to_lower)
{
lower_instructions_visitor v(what_to_lower);
visit_list_elements(&v, instructions);
return v.progress;
}
void
lower_instructions_visitor::sub_to_add_neg(ir_expression *ir)
{
ir->operation = ir_binop_add;
ir->operands[1] = new(ir) ir_expression(ir_unop_neg, ir->operands[1]->type,
ir->operands[1], NULL);
this->progress = true;
}
void
lower_instructions_visitor::div_to_mul_rcp(ir_expression *ir)
{
assert(ir->operands[1]->type->is_float());
/* New expression for the 1.0 / op1 */
ir_rvalue *expr;
expr = new(ir) ir_expression(ir_unop_rcp,
ir->operands[1]->type,
ir->operands[1]);
/* op0 / op1 -> op0 * (1.0 / op1) */
ir->operation = ir_binop_mul;
ir->operands[1] = expr;
this->progress = true;
}
void
lower_instructions_visitor::int_div_to_mul_rcp(ir_expression *ir)
{
assert(ir->operands[1]->type->is_integer());
/* Be careful with integer division -- we need to do it as a
* float and re-truncate, since rcp(n > 1) of an integer would
* just be 0.
*/
ir_rvalue *op0, *op1;
const struct glsl_type *vec_type;
vec_type = glsl_type::get_instance(GLSL_TYPE_FLOAT,
ir->operands[1]->type->vector_elements,
ir->operands[1]->type->matrix_columns);
if (ir->operands[1]->type->base_type == GLSL_TYPE_INT)
op1 = new(ir) ir_expression(ir_unop_i2f, vec_type, ir->operands[1], NULL);
else
op1 = new(ir) ir_expression(ir_unop_u2f, vec_type, ir->operands[1], NULL);
op1 = new(ir) ir_expression(ir_unop_rcp, op1->type, op1, NULL);
vec_type = glsl_type::get_instance(GLSL_TYPE_FLOAT,
ir->operands[0]->type->vector_elements,
ir->operands[0]->type->matrix_columns);
if (ir->operands[0]->type->base_type == GLSL_TYPE_INT)
op0 = new(ir) ir_expression(ir_unop_i2f, vec_type, ir->operands[0], NULL);
else
op0 = new(ir) ir_expression(ir_unop_u2f, vec_type, ir->operands[0], NULL);
vec_type = glsl_type::get_instance(GLSL_TYPE_FLOAT,
ir->type->vector_elements,
ir->type->matrix_columns);
op0 = new(ir) ir_expression(ir_binop_mul, vec_type, op0, op1);
if (ir->operands[1]->type->base_type == GLSL_TYPE_INT) {
ir->operation = ir_unop_f2i;
ir->operands[0] = op0;
} else {
ir->operation = ir_unop_i2u;
ir->operands[0] = new(ir) ir_expression(ir_unop_f2i, op0);
}
ir->operands[1] = NULL;
this->progress = true;
}
void
lower_instructions_visitor::exp_to_exp2(ir_expression *ir)
{
ir_constant *log2_e = new(ir) ir_constant(float(M_LOG2E));
ir->operation = ir_unop_exp2;
ir->operands[0] = new(ir) ir_expression(ir_binop_mul, ir->operands[0]->type,
ir->operands[0], log2_e);
this->progress = true;
}
void
lower_instructions_visitor::pow_to_exp2(ir_expression *ir)
{
ir_expression *const log2_x =
new(ir) ir_expression(ir_unop_log2, ir->operands[0]->type,
ir->operands[0]);
ir->operation = ir_unop_exp2;
ir->operands[0] = new(ir) ir_expression(ir_binop_mul, ir->operands[1]->type,
ir->operands[1], log2_x);
ir->operands[1] = NULL;
this->progress = true;
}
void
lower_instructions_visitor::log_to_log2(ir_expression *ir)
{
ir->operation = ir_binop_mul;
ir->operands[0] = new(ir) ir_expression(ir_unop_log2, ir->operands[0]->type,
ir->operands[0], NULL);
ir->operands[1] = new(ir) ir_constant(float(1.0 / M_LOG2E));
this->progress = true;
}
void
lower_instructions_visitor::mod_to_fract(ir_expression *ir)
{
ir_variable *temp = new(ir) ir_variable(ir->operands[1]->type, "mod_b",
ir_var_temporary);
this->base_ir->insert_before(temp);
ir_assignment *const assign =
new(ir) ir_assignment(new(ir) ir_dereference_variable(temp),
ir->operands[1], NULL);
this->base_ir->insert_before(assign);
ir_expression *const div_expr =
new(ir) ir_expression(ir_binop_div, ir->operands[0]->type,
ir->operands[0],
new(ir) ir_dereference_variable(temp));
/* Don't generate new IR that would need to be lowered in an additional
* pass.
*/
if (lowering(DIV_TO_MUL_RCP))
div_to_mul_rcp(div_expr);
ir_rvalue *expr = new(ir) ir_expression(ir_unop_fract,
ir->operands[0]->type,
div_expr,
NULL);
ir->operation = ir_binop_mul;
ir->operands[0] = new(ir) ir_dereference_variable(temp);
ir->operands[1] = expr;
this->progress = true;
}
void
lower_instructions_visitor::lrp_to_arith(ir_expression *ir)
{
/* (lrp x y a) -> x*(1-a) + y*a */
/* Save op2 */
ir_variable *temp = new(ir) ir_variable(ir->operands[2]->type, "lrp_factor",
ir_var_temporary);
this->base_ir->insert_before(temp);
this->base_ir->insert_before(assign(temp, ir->operands[2]));
ir_constant *one = new(ir) ir_constant(1.0f);
ir->operation = ir_binop_add;
ir->operands[0] = mul(ir->operands[0], sub(one, temp));
ir->operands[1] = mul(ir->operands[1], temp);
ir->operands[2] = NULL;
this->progress = true;
}
void
lower_instructions_visitor::bitfield_insert_to_bfm_bfi(ir_expression *ir)
{
/* Translates
* ir_quadop_bitfield_insert base insert offset bits
* into
* ir_triop_bfi (ir_binop_bfm bits offset) insert base
*/
ir_rvalue *base_expr = ir->operands[0];
ir->operation = ir_triop_bfi;
ir->operands[0] = new(ir) ir_expression(ir_binop_bfm,
ir->type->get_base_type(),
ir->operands[3],
ir->operands[2]);
/* ir->operands[1] is still the value to insert. */
ir->operands[2] = base_expr;
ir->operands[3] = NULL;
this->progress = true;
}
ir_visitor_status
lower_instructions_visitor::visit_leave(ir_expression *ir)
{
switch (ir->operation) {
case ir_binop_sub:
if (lowering(SUB_TO_ADD_NEG))
sub_to_add_neg(ir);
break;
case ir_binop_div:
if (ir->operands[1]->type->is_integer() && lowering(INT_DIV_TO_MUL_RCP))
int_div_to_mul_rcp(ir);
else if (ir->operands[1]->type->is_float() && lowering(DIV_TO_MUL_RCP))
div_to_mul_rcp(ir);
break;
case ir_unop_exp:
if (lowering(EXP_TO_EXP2))
exp_to_exp2(ir);
break;
case ir_unop_log:
if (lowering(LOG_TO_LOG2))
log_to_log2(ir);
break;
case ir_binop_mod:
if (lowering(MOD_TO_FRACT) && ir->type->is_float())
mod_to_fract(ir);
break;
case ir_binop_pow:
if (lowering(POW_TO_EXP2))
pow_to_exp2(ir);
break;
case ir_triop_lrp:
if (lowering(LRP_TO_ARITH))
lrp_to_arith(ir);
break;
case ir_quadop_bitfield_insert:
if (lowering(BITFIELD_INSERT_TO_BFM_BFI))
bitfield_insert_to_bfm_bfi(ir);
break;
default:
return visit_continue;
}
return visit_continue;
}