1080 lines
35 KiB
C
1080 lines
35 KiB
C
/*
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* Copyright © 2010 Intel Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*
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* Authors:
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* Eric Anholt <eric@anholt.net>
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*
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*/
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/** @file register_allocate.c
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*
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* Graph-coloring register allocator.
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*
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* The basic idea of graph coloring is to make a node in a graph for
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* every thing that needs a register (color) number assigned, and make
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* edges in the graph between nodes that interfere (can't be allocated
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* to the same register at the same time).
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*
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* During the "simplify" process, any any node with fewer edges than
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* there are registers means that that edge can get assigned a
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* register regardless of what its neighbors choose, so that node is
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* pushed on a stack and removed (with its edges) from the graph.
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* That likely causes other nodes to become trivially colorable as well.
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*
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* Then during the "select" process, nodes are popped off of that
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* stack, their edges restored, and assigned a color different from
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* their neighbors. Because they were pushed on the stack only when
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* they were trivially colorable, any color chosen won't interfere
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* with the registers to be popped later.
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*
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* The downside to most graph coloring is that real hardware often has
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* limitations, like registers that need to be allocated to a node in
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* pairs, or aligned on some boundary. This implementation follows
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* the paper "Retargetable Graph-Coloring Register Allocation for
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* Irregular Architectures" by Johan Runeson and Sven-Olof Nyström.
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*
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* In this system, there are register classes each containing various
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* registers, and registers may interfere with other registers. For
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* example, one might have a class of base registers, and a class of
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* aligned register pairs that would each interfere with their pair of
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* the base registers. Each node has a register class it needs to be
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* assigned to. Define p(B) to be the size of register class B, and
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* q(B,C) to be the number of registers in B that the worst choice
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* register in C could conflict with. Then, this system replaces the
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* basic graph coloring test of "fewer edges from this node than there
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* are registers" with "For this node of class B, the sum of q(B,C)
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* for each neighbor node of class C is less than pB".
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*
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* A nice feature of the pq test is that q(B,C) can be computed once
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* up front and stored in a 2-dimensional array, so that the cost of
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* coloring a node is constant with the number of registers. We do
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* this during ra_set_finalize().
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*/
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#include <stdbool.h>
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#include <stdlib.h>
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#include "blob.h"
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#include "ralloc.h"
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#include "util/bitset.h"
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#include "util/u_dynarray.h"
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#include "u_math.h"
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#include "register_allocate.h"
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#include "register_allocate_internal.h"
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/**
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* Creates a set of registers for the allocator.
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*
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* mem_ctx is a ralloc context for the allocator. The reg set may be freed
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* using ralloc_free().
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*/
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struct ra_regs *
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ra_alloc_reg_set(void *mem_ctx, unsigned int count, bool need_conflict_lists)
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{
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unsigned int i;
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struct ra_regs *regs;
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regs = rzalloc(mem_ctx, struct ra_regs);
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regs->count = count;
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regs->regs = rzalloc_array(regs, struct ra_reg, count);
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for (i = 0; i < count; i++) {
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regs->regs[i].conflicts = rzalloc_array(regs->regs, BITSET_WORD,
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BITSET_WORDS(count));
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BITSET_SET(regs->regs[i].conflicts, i);
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util_dynarray_init(®s->regs[i].conflict_list,
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need_conflict_lists ? regs->regs : NULL);
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if (need_conflict_lists)
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util_dynarray_append(®s->regs[i].conflict_list, unsigned int, i);
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}
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return regs;
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}
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/**
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* The register allocator by default prefers to allocate low register numbers,
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* since it was written for hardware (gen4/5 Intel) that is limited in its
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* multithreadedness by the number of registers used in a given shader.
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*
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* However, for hardware without that restriction, densely packed register
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* allocation can put serious constraints on instruction scheduling. This
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* function tells the allocator to rotate around the registers if possible as
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* it allocates the nodes.
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*/
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void
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ra_set_allocate_round_robin(struct ra_regs *regs)
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{
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regs->round_robin = true;
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}
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static void
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ra_add_conflict_list(struct ra_regs *regs, unsigned int r1, unsigned int r2)
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{
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struct ra_reg *reg1 = ®s->regs[r1];
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if (reg1->conflict_list.mem_ctx) {
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util_dynarray_append(®1->conflict_list, unsigned int, r2);
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}
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BITSET_SET(reg1->conflicts, r2);
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}
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void
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ra_add_reg_conflict(struct ra_regs *regs, unsigned int r1, unsigned int r2)
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{
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if (!BITSET_TEST(regs->regs[r1].conflicts, r2)) {
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ra_add_conflict_list(regs, r1, r2);
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ra_add_conflict_list(regs, r2, r1);
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}
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}
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/**
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* Adds a conflict between base_reg and reg, and also between reg and
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* anything that base_reg conflicts with.
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*
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* This can simplify code for setting up multiple register classes
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* which are aggregates of some base hardware registers, compared to
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* explicitly using ra_add_reg_conflict.
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*/
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void
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ra_add_transitive_reg_conflict(struct ra_regs *regs,
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unsigned int base_reg, unsigned int reg)
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{
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ra_add_reg_conflict(regs, reg, base_reg);
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util_dynarray_foreach(®s->regs[base_reg].conflict_list, unsigned int,
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r2p) {
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ra_add_reg_conflict(regs, reg, *r2p);
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}
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}
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/**
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* Set up conflicts between base_reg and it's two half registers reg0 and
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* reg1, but take care to not add conflicts between reg0 and reg1.
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*
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* This is useful for architectures where full size registers are aliased by
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* two half size registers (eg 32 bit float and 16 bit float registers).
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*/
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void
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ra_add_transitive_reg_pair_conflict(struct ra_regs *regs,
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unsigned int base_reg, unsigned int reg0, unsigned int reg1)
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{
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ra_add_reg_conflict(regs, reg0, base_reg);
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ra_add_reg_conflict(regs, reg1, base_reg);
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util_dynarray_foreach(®s->regs[base_reg].conflict_list, unsigned int, i) {
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unsigned int conflict = *i;
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if (conflict != reg1)
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ra_add_reg_conflict(regs, reg0, conflict);
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if (conflict != reg0)
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ra_add_reg_conflict(regs, reg1, conflict);
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}
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}
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/**
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* Makes every conflict on the given register transitive. In other words,
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* every register that conflicts with r will now conflict with every other
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* register conflicting with r.
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*
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* This can simplify code for setting up multiple register classes
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* which are aggregates of some base hardware registers, compared to
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* explicitly using ra_add_reg_conflict.
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*/
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void
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ra_make_reg_conflicts_transitive(struct ra_regs *regs, unsigned int r)
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{
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struct ra_reg *reg = ®s->regs[r];
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int c;
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BITSET_FOREACH_SET(c, reg->conflicts, regs->count) {
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struct ra_reg *other = ®s->regs[c];
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unsigned i;
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for (i = 0; i < BITSET_WORDS(regs->count); i++)
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other->conflicts[i] |= reg->conflicts[i];
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}
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}
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struct ra_class *
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ra_alloc_reg_class(struct ra_regs *regs)
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{
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struct ra_class *class;
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regs->classes = reralloc(regs->regs, regs->classes, struct ra_class *,
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regs->class_count + 1);
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class = rzalloc(regs, struct ra_class);
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class->regset = regs;
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/* Users may rely on the class index being allocated in order starting from 0. */
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class->index = regs->class_count++;
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regs->classes[class->index] = class;
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class->regs = rzalloc_array(class, BITSET_WORD, BITSET_WORDS(regs->count));
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return class;
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}
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/**
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* Creates a register class for contiguous register groups of a base register
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* set.
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*
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* A reg set using this type of register class must use only this type of
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* register class.
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*/
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struct ra_class *
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ra_alloc_contig_reg_class(struct ra_regs *regs, int contig_len)
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{
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struct ra_class *c = ra_alloc_reg_class(regs);
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assert(contig_len != 0);
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c->contig_len = contig_len;
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return c;
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}
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struct ra_class *
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ra_get_class_from_index(struct ra_regs *regs, unsigned int class)
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{
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return regs->classes[class];
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}
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unsigned int
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ra_class_index(struct ra_class *c)
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{
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return c->index;
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}
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void
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ra_class_add_reg(struct ra_class *class, unsigned int r)
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{
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assert(r < class->regset->count);
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assert(r + class->contig_len <= class->regset->count);
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BITSET_SET(class->regs, r);
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class->p++;
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}
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/**
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* Returns true if the register belongs to the given class.
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*/
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static bool
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reg_belongs_to_class(unsigned int r, struct ra_class *c)
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{
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return BITSET_TEST(c->regs, r);
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}
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/**
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* Must be called after all conflicts and register classes have been
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* set up and before the register set is used for allocation.
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* To avoid costly q value computation, use the q_values paramater
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* to pass precomputed q values to this function.
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*/
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void
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ra_set_finalize(struct ra_regs *regs, unsigned int **q_values)
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{
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unsigned int b, c;
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for (b = 0; b < regs->class_count; b++) {
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regs->classes[b]->q = ralloc_array(regs, unsigned int, regs->class_count);
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}
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if (q_values) {
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for (b = 0; b < regs->class_count; b++) {
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for (c = 0; c < regs->class_count; c++) {
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regs->classes[b]->q[c] = q_values[b][c];
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}
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}
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} else {
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/* Compute, for each class B and C, how many regs of B an
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* allocation to C could conflict with.
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*/
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for (b = 0; b < regs->class_count; b++) {
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for (c = 0; c < regs->class_count; c++) {
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struct ra_class *class_b = regs->classes[b];
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struct ra_class *class_c = regs->classes[c];
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if (class_b->contig_len && class_c->contig_len) {
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if (class_b->contig_len == 1 && class_c->contig_len == 1) {
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/* If both classes are single registers, then they only
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* conflict if there are any regs shared between them. This
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* is a cheap test for a common case.
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*/
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class_b->q[c] = 0;
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for (int i = 0; i < BITSET_WORDS(regs->count); i++) {
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if (class_b->regs[i] & class_c->regs[i]) {
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class_b->q[c] = 1;
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break;
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}
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}
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} else {
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int max_possible_conflicts = class_b->contig_len + class_c->contig_len - 1;
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unsigned int max_conflicts = 0;
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unsigned int rc;
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BITSET_FOREACH_SET(rc, regs->classes[c]->regs, regs->count) {
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int start = MAX2(0, (int)rc - class_b->contig_len + 1);
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int end = MIN2(regs->count, rc + class_c->contig_len);
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unsigned int conflicts = 0;
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for (int i = start; i < end; i++) {
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if (BITSET_TEST(class_b->regs, i))
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conflicts++;
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}
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max_conflicts = MAX2(max_conflicts, conflicts);
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/* Unless a class has some restriction like the register
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* bases are all aligned, then we should quickly find this
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* limit and exit the loop.
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*/
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if (max_conflicts == max_possible_conflicts)
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break;
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}
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class_b->q[c] = max_conflicts;
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}
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} else {
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/* If you're doing contiguous classes, you have to be all in
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* because I don't want to deal with it.
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*/
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assert(!class_b->contig_len && !class_c->contig_len);
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unsigned int rc;
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int max_conflicts = 0;
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BITSET_FOREACH_SET(rc, regs->classes[c]->regs, regs->count) {
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int conflicts = 0;
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util_dynarray_foreach(®s->regs[rc].conflict_list,
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unsigned int, rbp) {
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unsigned int rb = *rbp;
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if (reg_belongs_to_class(rb, regs->classes[b]))
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conflicts++;
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}
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max_conflicts = MAX2(max_conflicts, conflicts);
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}
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regs->classes[b]->q[c] = max_conflicts;
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}
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}
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}
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}
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for (b = 0; b < regs->count; b++) {
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util_dynarray_fini(®s->regs[b].conflict_list);
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}
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bool all_contig = true;
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for (int c = 0; c < regs->class_count; c++)
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all_contig &= regs->classes[c]->contig_len != 0;
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if (all_contig) {
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/* In this case, we never need the conflicts lists (and it would probably
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* be a mistake to look at conflicts when doing contiguous classes!), so
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* free them. TODO: Avoid the allocation in the first place.
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*/
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for (int i = 0; i < regs->count; i++) {
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ralloc_free(regs->regs[i].conflicts);
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regs->regs[i].conflicts = NULL;
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}
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}
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}
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void
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ra_set_serialize(const struct ra_regs *regs, struct blob *blob)
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{
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blob_write_uint32(blob, regs->count);
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blob_write_uint32(blob, regs->class_count);
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bool is_contig = regs->classes[0]->contig_len != 0;
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blob_write_uint8(blob, is_contig);
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if (!is_contig) {
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for (unsigned int r = 0; r < regs->count; r++) {
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struct ra_reg *reg = ®s->regs[r];
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blob_write_bytes(blob, reg->conflicts, BITSET_WORDS(regs->count) *
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sizeof(BITSET_WORD));
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assert(util_dynarray_num_elements(®->conflict_list, unsigned int) == 0);
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}
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}
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for (unsigned int c = 0; c < regs->class_count; c++) {
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struct ra_class *class = regs->classes[c];
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blob_write_bytes(blob, class->regs, BITSET_WORDS(regs->count) *
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sizeof(BITSET_WORD));
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blob_write_uint32(blob, class->contig_len);
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blob_write_uint32(blob, class->p);
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blob_write_bytes(blob, class->q, regs->class_count * sizeof(*class->q));
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}
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blob_write_uint32(blob, regs->round_robin);
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}
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struct ra_regs *
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ra_set_deserialize(void *mem_ctx, struct blob_reader *blob)
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{
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unsigned int reg_count = blob_read_uint32(blob);
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unsigned int class_count = blob_read_uint32(blob);
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bool is_contig = blob_read_uint8(blob);
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struct ra_regs *regs = ra_alloc_reg_set(mem_ctx, reg_count, false);
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assert(regs->count == reg_count);
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if (is_contig) {
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for (int i = 0; i < regs->count; i++) {
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ralloc_free(regs->regs[i].conflicts);
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regs->regs[i].conflicts = NULL;
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}
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} else {
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for (unsigned int r = 0; r < reg_count; r++) {
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struct ra_reg *reg = ®s->regs[r];
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blob_copy_bytes(blob, reg->conflicts, BITSET_WORDS(reg_count) *
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sizeof(BITSET_WORD));
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}
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}
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assert(regs->classes == NULL);
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regs->classes = ralloc_array(regs->regs, struct ra_class *, class_count);
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regs->class_count = class_count;
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for (unsigned int c = 0; c < class_count; c++) {
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struct ra_class *class = rzalloc(regs, struct ra_class);
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regs->classes[c] = class;
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class->regset = regs;
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class->index = c;
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class->regs = ralloc_array(class, BITSET_WORD, BITSET_WORDS(reg_count));
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blob_copy_bytes(blob, class->regs, BITSET_WORDS(reg_count) *
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sizeof(BITSET_WORD));
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class->contig_len = blob_read_uint32(blob);
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class->p = blob_read_uint32(blob);
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class->q = ralloc_array(regs->classes[c], unsigned int, class_count);
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blob_copy_bytes(blob, class->q, class_count * sizeof(*class->q));
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}
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regs->round_robin = blob_read_uint32(blob);
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return regs;
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}
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static uint64_t
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ra_get_num_adjacency_bits(uint64_t n)
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{
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return (n * (n - 1)) / 2;
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}
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static uint64_t
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ra_get_adjacency_bit_index(unsigned n1, unsigned n2)
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{
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assert(n1 != n2);
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unsigned k1 = MAX2(n1, n2);
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unsigned k2 = MIN2(n1, n2);
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return ra_get_num_adjacency_bits(k1) + k2;
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}
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|
|
static bool
|
|
ra_test_adjacency_bit(struct ra_graph *g, unsigned n1, unsigned n2)
|
|
{
|
|
uint64_t index = ra_get_adjacency_bit_index(n1, n2);
|
|
return BITSET_TEST(g->adjacency, index);
|
|
}
|
|
|
|
static void
|
|
ra_set_adjacency_bit(struct ra_graph *g, unsigned n1, unsigned n2)
|
|
{
|
|
unsigned index = ra_get_adjacency_bit_index(n1, n2);
|
|
BITSET_SET(g->adjacency, index);
|
|
}
|
|
|
|
static void
|
|
ra_clear_adjacency_bit(struct ra_graph *g, unsigned n1, unsigned n2)
|
|
{
|
|
unsigned index = ra_get_adjacency_bit_index(n1, n2);
|
|
BITSET_CLEAR(g->adjacency, index);
|
|
}
|
|
|
|
static void
|
|
ra_add_node_adjacency(struct ra_graph *g, unsigned int n1, unsigned int n2)
|
|
{
|
|
assert(n1 != n2);
|
|
|
|
int n1_class = g->nodes[n1].class;
|
|
int n2_class = g->nodes[n2].class;
|
|
g->nodes[n1].q_total += g->regs->classes[n1_class]->q[n2_class];
|
|
|
|
util_dynarray_append(&g->nodes[n1].adjacency_list, unsigned int, n2);
|
|
}
|
|
|
|
static void
|
|
ra_node_remove_adjacency(struct ra_graph *g, unsigned int n1, unsigned int n2)
|
|
{
|
|
assert(n1 != n2);
|
|
ra_clear_adjacency_bit(g, n1, n2);
|
|
|
|
int n1_class = g->nodes[n1].class;
|
|
int n2_class = g->nodes[n2].class;
|
|
g->nodes[n1].q_total -= g->regs->classes[n1_class]->q[n2_class];
|
|
|
|
util_dynarray_delete_unordered(&g->nodes[n1].adjacency_list, unsigned int,
|
|
n2);
|
|
}
|
|
|
|
static void
|
|
ra_realloc_interference_graph(struct ra_graph *g, unsigned int alloc)
|
|
{
|
|
if (alloc <= g->alloc)
|
|
return;
|
|
|
|
/* If we always have a whole number of BITSET_WORDs, it makes it much
|
|
* easier to memset the top of the growing bitsets.
|
|
*/
|
|
assert(g->alloc % BITSET_WORDBITS == 0);
|
|
alloc = align64(alloc, BITSET_WORDBITS);
|
|
g->nodes = rerzalloc(g, g->nodes, struct ra_node, g->alloc, alloc);
|
|
g->adjacency = rerzalloc(g, g->adjacency, BITSET_WORD,
|
|
BITSET_WORDS(ra_get_num_adjacency_bits(g->alloc)),
|
|
BITSET_WORDS(ra_get_num_adjacency_bits(alloc)));
|
|
|
|
/* Initialize new nodes. */
|
|
for (unsigned i = g->alloc; i < alloc; i++) {
|
|
struct ra_node* node = g->nodes + i;
|
|
util_dynarray_init(&node->adjacency_list, g);
|
|
node->q_total = 0;
|
|
node->forced_reg = NO_REG;
|
|
node->reg = NO_REG;
|
|
}
|
|
|
|
/* These are scratch values and don't need to be zeroed. We'll clear them
|
|
* as part of ra_select() setup.
|
|
*/
|
|
unsigned bitset_count = BITSET_WORDS(alloc);
|
|
g->tmp.stack = reralloc(g, g->tmp.stack, unsigned int, alloc);
|
|
g->tmp.in_stack = reralloc(g, g->tmp.in_stack, BITSET_WORD, bitset_count);
|
|
|
|
g->tmp.reg_assigned = reralloc(g, g->tmp.reg_assigned, BITSET_WORD,
|
|
bitset_count);
|
|
g->tmp.pq_test = reralloc(g, g->tmp.pq_test, BITSET_WORD, bitset_count);
|
|
g->tmp.min_q_total = reralloc(g, g->tmp.min_q_total, unsigned int,
|
|
bitset_count);
|
|
g->tmp.min_q_node = reralloc(g, g->tmp.min_q_node, unsigned int,
|
|
bitset_count);
|
|
|
|
g->alloc = alloc;
|
|
}
|
|
|
|
struct ra_graph *
|
|
ra_alloc_interference_graph(struct ra_regs *regs, unsigned int count)
|
|
{
|
|
struct ra_graph *g;
|
|
|
|
g = rzalloc(NULL, struct ra_graph);
|
|
g->regs = regs;
|
|
g->count = count;
|
|
ra_realloc_interference_graph(g, count);
|
|
|
|
return g;
|
|
}
|
|
|
|
void
|
|
ra_resize_interference_graph(struct ra_graph *g, unsigned int count)
|
|
{
|
|
g->count = count;
|
|
if (count > g->alloc)
|
|
ra_realloc_interference_graph(g, g->alloc * 2);
|
|
}
|
|
|
|
void ra_set_select_reg_callback(struct ra_graph *g,
|
|
ra_select_reg_callback callback,
|
|
void *data)
|
|
{
|
|
g->select_reg_callback = callback;
|
|
g->select_reg_callback_data = data;
|
|
}
|
|
|
|
void
|
|
ra_set_node_class(struct ra_graph *g,
|
|
unsigned int n, struct ra_class *class)
|
|
{
|
|
g->nodes[n].class = class->index;
|
|
}
|
|
|
|
struct ra_class *
|
|
ra_get_node_class(struct ra_graph *g,
|
|
unsigned int n)
|
|
{
|
|
return g->regs->classes[g->nodes[n].class];
|
|
}
|
|
|
|
unsigned int
|
|
ra_add_node(struct ra_graph *g, struct ra_class *class)
|
|
{
|
|
unsigned int n = g->count;
|
|
ra_resize_interference_graph(g, g->count + 1);
|
|
|
|
ra_set_node_class(g, n, class);
|
|
|
|
return n;
|
|
}
|
|
|
|
void
|
|
ra_add_node_interference(struct ra_graph *g,
|
|
unsigned int n1, unsigned int n2)
|
|
{
|
|
assert(n1 < g->count && n2 < g->count);
|
|
if (n1 != n2 && !ra_test_adjacency_bit(g, n1, n2)) {
|
|
ra_set_adjacency_bit(g, n1, n2);
|
|
ra_add_node_adjacency(g, n1, n2);
|
|
ra_add_node_adjacency(g, n2, n1);
|
|
}
|
|
}
|
|
|
|
void
|
|
ra_reset_node_interference(struct ra_graph *g, unsigned int n)
|
|
{
|
|
util_dynarray_foreach(&g->nodes[n].adjacency_list, unsigned int, n2p) {
|
|
ra_node_remove_adjacency(g, *n2p, n);
|
|
}
|
|
|
|
util_dynarray_clear(&g->nodes[n].adjacency_list);
|
|
}
|
|
|
|
static void
|
|
update_pq_info(struct ra_graph *g, unsigned int n)
|
|
{
|
|
int i = n / BITSET_WORDBITS;
|
|
int n_class = g->nodes[n].class;
|
|
if (g->nodes[n].tmp.q_total < g->regs->classes[n_class]->p) {
|
|
BITSET_SET(g->tmp.pq_test, n);
|
|
} else if (g->tmp.min_q_total[i] != UINT_MAX) {
|
|
/* Only update min_q_total and min_q_node if min_q_total != UINT_MAX so
|
|
* that we don't update while we have stale data and accidentally mark
|
|
* it as non-stale. Also, in order to remain consistent with the old
|
|
* naive implementation of the algorithm, we do a lexicographical sort
|
|
* to ensure that we always choose the node with the highest node index.
|
|
*/
|
|
if (g->nodes[n].tmp.q_total < g->tmp.min_q_total[i] ||
|
|
(g->nodes[n].tmp.q_total == g->tmp.min_q_total[i] &&
|
|
n > g->tmp.min_q_node[i])) {
|
|
g->tmp.min_q_total[i] = g->nodes[n].tmp.q_total;
|
|
g->tmp.min_q_node[i] = n;
|
|
}
|
|
}
|
|
}
|
|
|
|
static void
|
|
add_node_to_stack(struct ra_graph *g, unsigned int n)
|
|
{
|
|
int n_class = g->nodes[n].class;
|
|
|
|
assert(!BITSET_TEST(g->tmp.in_stack, n));
|
|
|
|
util_dynarray_foreach(&g->nodes[n].adjacency_list, unsigned int, n2p) {
|
|
unsigned int n2 = *n2p;
|
|
unsigned int n2_class = g->nodes[n2].class;
|
|
|
|
if (!BITSET_TEST(g->tmp.in_stack, n2) &&
|
|
!BITSET_TEST(g->tmp.reg_assigned, n2)) {
|
|
assert(g->nodes[n2].tmp.q_total >= g->regs->classes[n2_class]->q[n_class]);
|
|
g->nodes[n2].tmp.q_total -= g->regs->classes[n2_class]->q[n_class];
|
|
update_pq_info(g, n2);
|
|
}
|
|
}
|
|
|
|
g->tmp.stack[g->tmp.stack_count] = n;
|
|
g->tmp.stack_count++;
|
|
BITSET_SET(g->tmp.in_stack, n);
|
|
|
|
/* Flag the min_q_total for n's block as dirty so it gets recalculated */
|
|
g->tmp.min_q_total[n / BITSET_WORDBITS] = UINT_MAX;
|
|
}
|
|
|
|
/**
|
|
* Simplifies the interference graph by pushing all
|
|
* trivially-colorable nodes into a stack of nodes to be colored,
|
|
* removing them from the graph, and rinsing and repeating.
|
|
*
|
|
* If we encounter a case where we can't push any nodes on the stack, then
|
|
* we optimistically choose a node and push it on the stack. We heuristically
|
|
* push the node with the lowest total q value, since it has the fewest
|
|
* neighbors and therefore is most likely to be allocated.
|
|
*/
|
|
static void
|
|
ra_simplify(struct ra_graph *g)
|
|
{
|
|
bool progress = true;
|
|
unsigned int stack_optimistic_start = UINT_MAX;
|
|
|
|
/* Figure out the high bit and bit mask for the first iteration of a loop
|
|
* over BITSET_WORDs.
|
|
*/
|
|
const unsigned int top_word_high_bit = (g->count - 1) % BITSET_WORDBITS;
|
|
|
|
/* Do a quick pre-pass to set things up */
|
|
g->tmp.stack_count = 0;
|
|
for (int i = BITSET_WORDS(g->count) - 1, high_bit = top_word_high_bit;
|
|
i >= 0; i--, high_bit = BITSET_WORDBITS - 1) {
|
|
g->tmp.in_stack[i] = 0;
|
|
g->tmp.reg_assigned[i] = 0;
|
|
g->tmp.pq_test[i] = 0;
|
|
g->tmp.min_q_total[i] = UINT_MAX;
|
|
g->tmp.min_q_node[i] = UINT_MAX;
|
|
for (int j = high_bit; j >= 0; j--) {
|
|
unsigned int n = i * BITSET_WORDBITS + j;
|
|
g->nodes[n].reg = g->nodes[n].forced_reg;
|
|
g->nodes[n].tmp.q_total = g->nodes[n].q_total;
|
|
if (g->nodes[n].reg != NO_REG)
|
|
g->tmp.reg_assigned[i] |= BITSET_BIT(j);
|
|
update_pq_info(g, n);
|
|
}
|
|
}
|
|
|
|
while (progress) {
|
|
unsigned int min_q_total = UINT_MAX;
|
|
unsigned int min_q_node = UINT_MAX;
|
|
|
|
progress = false;
|
|
|
|
for (int i = BITSET_WORDS(g->count) - 1, high_bit = top_word_high_bit;
|
|
i >= 0; i--, high_bit = BITSET_WORDBITS - 1) {
|
|
BITSET_WORD mask = ~(BITSET_WORD)0 >> (31 - high_bit);
|
|
|
|
BITSET_WORD skip = g->tmp.in_stack[i] | g->tmp.reg_assigned[i];
|
|
if (skip == mask)
|
|
continue;
|
|
|
|
BITSET_WORD pq = g->tmp.pq_test[i] & ~skip;
|
|
if (pq) {
|
|
/* In this case, we have stuff we can immediately take off the
|
|
* stack. This also means that we're guaranteed to make progress
|
|
* and we don't need to bother updating lowest_q_total because we
|
|
* know we're going to loop again before attempting to do anything
|
|
* optimistic.
|
|
*/
|
|
for (int j = high_bit; j >= 0; j--) {
|
|
if (pq & BITSET_BIT(j)) {
|
|
unsigned int n = i * BITSET_WORDBITS + j;
|
|
assert(n < g->count);
|
|
add_node_to_stack(g, n);
|
|
/* add_node_to_stack() may update pq_test for this word so
|
|
* we need to update our local copy.
|
|
*/
|
|
pq = g->tmp.pq_test[i] & ~skip;
|
|
progress = true;
|
|
}
|
|
}
|
|
} else if (!progress) {
|
|
if (g->tmp.min_q_total[i] == UINT_MAX) {
|
|
/* The min_q_total and min_q_node are dirty because we added
|
|
* one of these nodes to the stack. It needs to be
|
|
* recalculated.
|
|
*/
|
|
for (int j = high_bit; j >= 0; j--) {
|
|
if (skip & BITSET_BIT(j))
|
|
continue;
|
|
|
|
unsigned int n = i * BITSET_WORDBITS + j;
|
|
assert(n < g->count);
|
|
if (g->nodes[n].tmp.q_total < g->tmp.min_q_total[i]) {
|
|
g->tmp.min_q_total[i] = g->nodes[n].tmp.q_total;
|
|
g->tmp.min_q_node[i] = n;
|
|
}
|
|
}
|
|
}
|
|
if (g->tmp.min_q_total[i] < min_q_total) {
|
|
min_q_node = g->tmp.min_q_node[i];
|
|
min_q_total = g->tmp.min_q_total[i];
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!progress && min_q_total != UINT_MAX) {
|
|
if (stack_optimistic_start == UINT_MAX)
|
|
stack_optimistic_start = g->tmp.stack_count;
|
|
|
|
add_node_to_stack(g, min_q_node);
|
|
progress = true;
|
|
}
|
|
}
|
|
|
|
g->tmp.stack_optimistic_start = stack_optimistic_start;
|
|
}
|
|
|
|
bool
|
|
ra_class_allocations_conflict(struct ra_class *c1, unsigned int r1,
|
|
struct ra_class *c2, unsigned int r2)
|
|
{
|
|
if (c1->contig_len) {
|
|
assert(c2->contig_len);
|
|
|
|
int r1_end = r1 + c1->contig_len;
|
|
int r2_end = r2 + c2->contig_len;
|
|
return !(r2 >= r1_end || r1 >= r2_end);
|
|
} else {
|
|
return BITSET_TEST(c1->regset->regs[r1].conflicts, r2);
|
|
}
|
|
}
|
|
|
|
static struct ra_node *
|
|
ra_find_conflicting_neighbor(struct ra_graph *g, unsigned int n, unsigned int r)
|
|
{
|
|
util_dynarray_foreach(&g->nodes[n].adjacency_list, unsigned int, n2p) {
|
|
unsigned int n2 = *n2p;
|
|
|
|
/* If our adjacent node is in the stack, it's not allocated yet. */
|
|
if (!BITSET_TEST(g->tmp.in_stack, n2) &&
|
|
ra_class_allocations_conflict(g->regs->classes[g->nodes[n].class], r,
|
|
g->regs->classes[g->nodes[n2].class], g->nodes[n2].reg)) {
|
|
return &g->nodes[n2];
|
|
}
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
|
|
/* Computes a bitfield of what regs are available for a given register
|
|
* selection.
|
|
*
|
|
* This lets drivers implement a more complicated policy than our simple first
|
|
* or round robin policies (which don't require knowing the whole bitset)
|
|
*/
|
|
static bool
|
|
ra_compute_available_regs(struct ra_graph *g, unsigned int n, BITSET_WORD *regs)
|
|
{
|
|
struct ra_class *c = g->regs->classes[g->nodes[n].class];
|
|
|
|
/* Populate with the set of regs that are in the node's class. */
|
|
memcpy(regs, c->regs, BITSET_WORDS(g->regs->count) * sizeof(BITSET_WORD));
|
|
|
|
/* Remove any regs that conflict with nodes that we're adjacent to and have
|
|
* already colored.
|
|
*/
|
|
util_dynarray_foreach(&g->nodes[n].adjacency_list, unsigned int, n2p) {
|
|
struct ra_node *n2 = &g->nodes[*n2p];
|
|
struct ra_class *n2c = g->regs->classes[n2->class];
|
|
|
|
if (!BITSET_TEST(g->tmp.in_stack, *n2p)) {
|
|
if (c->contig_len) {
|
|
int start = MAX2(0, (int)n2->reg - c->contig_len + 1);
|
|
int end = MIN2(g->regs->count, n2->reg + n2c->contig_len);
|
|
for (unsigned i = start; i < end; i++)
|
|
BITSET_CLEAR(regs, i);
|
|
} else {
|
|
for (int j = 0; j < BITSET_WORDS(g->regs->count); j++)
|
|
regs[j] &= ~g->regs->regs[n2->reg].conflicts[j];
|
|
}
|
|
}
|
|
}
|
|
|
|
for (int i = 0; i < BITSET_WORDS(g->regs->count); i++) {
|
|
if (regs[i])
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* Pops nodes from the stack back into the graph, coloring them with
|
|
* registers as they go.
|
|
*
|
|
* If all nodes were trivially colorable, then this must succeed. If
|
|
* not (optimistic coloring), then it may return false;
|
|
*/
|
|
static bool
|
|
ra_select(struct ra_graph *g)
|
|
{
|
|
int start_search_reg = 0;
|
|
BITSET_WORD *select_regs = NULL;
|
|
|
|
if (g->select_reg_callback)
|
|
select_regs = malloc(BITSET_WORDS(g->regs->count) * sizeof(BITSET_WORD));
|
|
|
|
while (g->tmp.stack_count != 0) {
|
|
unsigned int ri;
|
|
unsigned int r = -1;
|
|
int n = g->tmp.stack[g->tmp.stack_count - 1];
|
|
struct ra_class *c = g->regs->classes[g->nodes[n].class];
|
|
|
|
/* set this to false even if we return here so that
|
|
* ra_get_best_spill_node() considers this node later.
|
|
*/
|
|
BITSET_CLEAR(g->tmp.in_stack, n);
|
|
|
|
if (g->select_reg_callback) {
|
|
if (!ra_compute_available_regs(g, n, select_regs)) {
|
|
free(select_regs);
|
|
return false;
|
|
}
|
|
|
|
r = g->select_reg_callback(n, select_regs, g->select_reg_callback_data);
|
|
assert(r < g->regs->count);
|
|
} else {
|
|
/* Find the lowest-numbered reg which is not used by a member
|
|
* of the graph adjacent to us.
|
|
*/
|
|
for (ri = 0; ri < g->regs->count; ri++) {
|
|
r = (start_search_reg + ri) % g->regs->count;
|
|
if (!reg_belongs_to_class(r, c))
|
|
continue;
|
|
|
|
struct ra_node *conflicting = ra_find_conflicting_neighbor(g, n, r);
|
|
if (!conflicting) {
|
|
/* Found a reg! */
|
|
break;
|
|
}
|
|
if (g->regs->classes[conflicting->class]->contig_len) {
|
|
/* Skip to point at the last base reg of the conflicting reg
|
|
* allocation -- the loop will increment us to check the next reg
|
|
* after the conflicting allocaiton.
|
|
*/
|
|
unsigned conflicting_end = (conflicting->reg +
|
|
g->regs->classes[conflicting->class]->contig_len - 1);
|
|
assert(conflicting_end >= r);
|
|
ri += conflicting_end - r;
|
|
}
|
|
}
|
|
|
|
if (ri >= g->regs->count)
|
|
return false;
|
|
}
|
|
|
|
g->nodes[n].reg = r;
|
|
g->tmp.stack_count--;
|
|
|
|
/* Rotate the starting point except for any nodes above the lowest
|
|
* optimistically colorable node. The likelihood that we will succeed
|
|
* at allocating optimistically colorable nodes is highly dependent on
|
|
* the way that the previous nodes popped off the stack are laid out.
|
|
* The round-robin strategy increases the fragmentation of the register
|
|
* file and decreases the number of nearby nodes assigned to the same
|
|
* color, what increases the likelihood of spilling with respect to the
|
|
* dense packing strategy.
|
|
*/
|
|
if (g->regs->round_robin &&
|
|
g->tmp.stack_count - 1 <= g->tmp.stack_optimistic_start)
|
|
start_search_reg = r + 1;
|
|
}
|
|
|
|
free(select_regs);
|
|
|
|
return true;
|
|
}
|
|
|
|
bool
|
|
ra_allocate(struct ra_graph *g)
|
|
{
|
|
ra_simplify(g);
|
|
return ra_select(g);
|
|
}
|
|
|
|
unsigned int
|
|
ra_get_node_reg(struct ra_graph *g, unsigned int n)
|
|
{
|
|
if (g->nodes[n].forced_reg != NO_REG)
|
|
return g->nodes[n].forced_reg;
|
|
else
|
|
return g->nodes[n].reg;
|
|
}
|
|
|
|
/**
|
|
* Forces a node to a specific register. This can be used to avoid
|
|
* creating a register class containing one node when handling data
|
|
* that must live in a fixed location and is known to not conflict
|
|
* with other forced register assignment (as is common with shader
|
|
* input data). These nodes do not end up in the stack during
|
|
* ra_simplify(), and thus at ra_select() time it is as if they were
|
|
* the first popped off the stack and assigned their fixed locations.
|
|
* Nodes that use this function do not need to be assigned a register
|
|
* class.
|
|
*
|
|
* Must be called before ra_simplify().
|
|
*/
|
|
void
|
|
ra_set_node_reg(struct ra_graph *g, unsigned int n, unsigned int reg)
|
|
{
|
|
g->nodes[n].forced_reg = reg;
|
|
}
|
|
|
|
static float
|
|
ra_get_spill_benefit(struct ra_graph *g, unsigned int n)
|
|
{
|
|
float benefit = 0;
|
|
int n_class = g->nodes[n].class;
|
|
|
|
/* Define the benefit of eliminating an interference between n, n2
|
|
* through spilling as q(C, B) / p(C). This is similar to the
|
|
* "count number of edges" approach of traditional graph coloring,
|
|
* but takes classes into account.
|
|
*/
|
|
util_dynarray_foreach(&g->nodes[n].adjacency_list, unsigned int, n2p) {
|
|
unsigned int n2 = *n2p;
|
|
unsigned int n2_class = g->nodes[n2].class;
|
|
benefit += ((float)g->regs->classes[n_class]->q[n2_class] /
|
|
g->regs->classes[n_class]->p);
|
|
}
|
|
|
|
return benefit;
|
|
}
|
|
|
|
/**
|
|
* Returns a node number to be spilled according to the cost/benefit using
|
|
* the pq test, or -1 if there are no spillable nodes.
|
|
*/
|
|
int
|
|
ra_get_best_spill_node(struct ra_graph *g)
|
|
{
|
|
unsigned int best_node = -1;
|
|
float best_benefit = 0.0;
|
|
unsigned int n;
|
|
|
|
/* Consider any nodes that we colored successfully or the node we failed to
|
|
* color for spilling. When we failed to color a node in ra_select(), we
|
|
* only considered these nodes, so spilling any other ones would not result
|
|
* in us making progress.
|
|
*/
|
|
for (n = 0; n < g->count; n++) {
|
|
float cost = g->nodes[n].spill_cost;
|
|
float benefit;
|
|
|
|
if (cost <= 0.0f)
|
|
continue;
|
|
|
|
if (BITSET_TEST(g->tmp.in_stack, n))
|
|
continue;
|
|
|
|
benefit = ra_get_spill_benefit(g, n);
|
|
|
|
if (benefit / cost > best_benefit) {
|
|
best_benefit = benefit / cost;
|
|
best_node = n;
|
|
}
|
|
}
|
|
|
|
return best_node;
|
|
}
|
|
|
|
/**
|
|
* Only nodes with a spill cost set (cost != 0.0) will be considered
|
|
* for register spilling.
|
|
*/
|
|
void
|
|
ra_set_node_spill_cost(struct ra_graph *g, unsigned int n, float cost)
|
|
{
|
|
g->nodes[n].spill_cost = cost;
|
|
}
|