* IN THE SOFTWARE.
*/
-#include "main/macros.h"
#include "util/register_allocate.h"
#include "brw_vec4.h"
-#include "brw_vs.h"
#include "brw_cfg.h"
using namespace brw;
static void
assign(unsigned int *reg_hw_locations, backend_reg *reg)
{
- if (reg->file == GRF) {
- reg->reg = reg_hw_locations[reg->reg] + reg->reg_offset;
- reg->reg_offset = 0;
+ if (reg->file == VGRF) {
+ reg->nr = reg_hw_locations[reg->nr] + reg->offset / REG_SIZE;
+ reg->offset %= REG_SIZE;
}
}
}
foreach_block_and_inst(block, vec4_instruction, inst, cfg) {
- if (inst->dst.file == GRF)
- virtual_grf_used[inst->dst.reg] = true;
+ if (inst->dst.file == VGRF)
+ virtual_grf_used[inst->dst.nr] = true;
for (unsigned i = 0; i < 3; i++) {
- if (inst->src[i].file == GRF)
- virtual_grf_used[inst->src[i].reg] = true;
+ if (inst->src[i].file == VGRF)
+ virtual_grf_used[inst->src[i].nr] = true;
}
}
ralloc_free(compiler->vec4_reg_set.ra_reg_to_grf);
compiler->vec4_reg_set.ra_reg_to_grf = ralloc_array(compiler, uint8_t, ra_reg_count);
ralloc_free(compiler->vec4_reg_set.regs);
- compiler->vec4_reg_set.regs = ra_alloc_reg_set(compiler, ra_reg_count);
+ compiler->vec4_reg_set.regs = ra_alloc_reg_set(compiler, ra_reg_count, false);
if (compiler->devinfo->gen >= 6)
ra_set_allocate_round_robin(compiler->vec4_reg_set.regs);
ralloc_free(compiler->vec4_reg_set.classes);
for (int base_reg = j;
base_reg < j + class_sizes[i];
base_reg++) {
- ra_add_transitive_reg_conflict(compiler->vec4_reg_set.regs, base_reg, reg);
+ ra_add_reg_conflict(compiler->vec4_reg_set.regs, base_reg, reg);
}
reg++;
}
assert(reg == ra_reg_count);
+ for (int reg = 0; reg < base_reg_count; reg++)
+ ra_make_reg_conflicts_transitive(compiler->vec4_reg_set.regs, reg);
+
ra_set_finalize(compiler->vec4_reg_set.regs, q_values);
for (int i = 0; i < MAX_VGRF_SIZE; i++)
}
}
+ /* Certain instructions can't safely use the same register for their
+ * sources and destination. Add interference.
+ */
+ foreach_block_and_inst(block, vec4_instruction, inst, cfg) {
+ if (inst->dst.file == VGRF && inst->has_source_and_destination_hazard()) {
+ for (unsigned i = 0; i < 3; i++) {
+ if (inst->src[i].file == VGRF) {
+ ra_add_node_interference(g, inst->dst.nr, inst->src[i].nr);
+ }
+ }
+ }
+ }
+
setup_payload_interference(g, first_payload_node, node_count);
if (!ra_allocate(g)) {
return true;
}
+/**
+ * When we decide to spill a register, instead of blindly spilling every use,
+ * save unspills when the spill register is used (read) in consecutive
+ * instructions. This can potentially save a bunch of unspills that would
+ * have very little impact in register allocation anyway.
+ *
+ * Notice that we need to account for this behavior when spilling a register
+ * and when evaluating spilling costs. This function is designed so it can
+ * be called from both places and avoid repeating the logic.
+ *
+ * - When we call this function from spill_reg(), we pass in scratch_reg the
+ * actual unspill/spill register that we want to reuse in the current
+ * instruction.
+ *
+ * - When we call this from evaluate_spill_costs(), we pass the register for
+ * which we are evaluating spilling costs.
+ *
+ * In either case, we check if the previous instructions read scratch_reg until
+ * we find one that writes to it with a compatible mask or does not read/write
+ * scratch_reg at all.
+ */
+static bool
+can_use_scratch_for_source(const vec4_instruction *inst, unsigned i,
+ unsigned scratch_reg)
+{
+ assert(inst->src[i].file == VGRF);
+ bool prev_inst_read_scratch_reg = false;
+
+ /* See if any previous source in the same instructions reads scratch_reg */
+ for (unsigned n = 0; n < i; n++) {
+ if (inst->src[n].file == VGRF && inst->src[n].nr == scratch_reg)
+ prev_inst_read_scratch_reg = true;
+ }
+
+ /* Now check if previous instructions read/write scratch_reg */
+ for (vec4_instruction *prev_inst = (vec4_instruction *) inst->prev;
+ !prev_inst->is_head_sentinel();
+ prev_inst = (vec4_instruction *) prev_inst->prev) {
+
+ /* If the previous instruction writes to scratch_reg then we can reuse
+ * it if the write is not conditional and the channels we write are
+ * compatible with our read mask
+ */
+ if (prev_inst->dst.file == VGRF && prev_inst->dst.nr == scratch_reg) {
+ return (!prev_inst->predicate || prev_inst->opcode == BRW_OPCODE_SEL) &&
+ (brw_mask_for_swizzle(inst->src[i].swizzle) &
+ ~prev_inst->dst.writemask) == 0;
+ }
+
+ /* Skip scratch read/writes so that instructions generated by spilling
+ * other registers (that won't read/write scratch_reg) do not stop us from
+ * reusing scratch_reg for this instruction.
+ */
+ if (prev_inst->opcode == SHADER_OPCODE_GEN4_SCRATCH_WRITE ||
+ prev_inst->opcode == SHADER_OPCODE_GEN4_SCRATCH_READ)
+ continue;
+
+ /* If the previous instruction does not write to scratch_reg, then check
+ * if it reads it
+ */
+ int n;
+ for (n = 0; n < 3; n++) {
+ if (prev_inst->src[n].file == VGRF &&
+ prev_inst->src[n].nr == scratch_reg) {
+ prev_inst_read_scratch_reg = true;
+ break;
+ }
+ }
+ if (n == 3) {
+ /* The previous instruction does not read scratch_reg. At this point,
+ * if no previous instruction has read scratch_reg it means that we
+ * will need to unspill it here and we can't reuse it (so we return
+ * false). Otherwise, if we found at least one consecutive instruction
+ * that read scratch_reg, then we know that we got here from
+ * evaluate_spill_costs (since for the spill_reg path any block of
+ * consecutive instructions using scratch_reg must start with a write
+ * to that register, so we would've exited the loop in the check for
+ * the write that we have at the start of this loop), and in that case
+ * it means that we found the point at which the scratch_reg would be
+ * unspilled. Since we always unspill a full vec4, it means that we
+ * have all the channels available and we can just return true to
+ * signal that we can reuse the register in the current instruction
+ * too.
+ */
+ return prev_inst_read_scratch_reg;
+ }
+ }
+
+ return prev_inst_read_scratch_reg;
+}
+
void
vec4_visitor::evaluate_spill_costs(float *spill_costs, bool *no_spill)
{
*/
foreach_block_and_inst(block, vec4_instruction, inst, cfg) {
for (unsigned int i = 0; i < 3; i++) {
- if (inst->src[i].file == GRF) {
- spill_costs[inst->src[i].reg] += loop_scale;
- if (inst->src[i].reladdr)
- no_spill[inst->src[i].reg] = true;
- }
+ if (inst->src[i].file == VGRF) {
+ /* We will only unspill src[i] it it wasn't unspilled for the
+ * previous instruction, in which case we'll just reuse the scratch
+ * reg for this instruction.
+ */
+ if (!can_use_scratch_for_source(inst, i, inst->src[i].nr)) {
+ spill_costs[inst->src[i].nr] += loop_scale;
+ if (inst->src[i].reladdr ||
+ inst->src[i].offset % REG_SIZE != 0)
+ no_spill[inst->src[i].nr] = true;
+ }
+ }
}
- if (inst->dst.file == GRF) {
- spill_costs[inst->dst.reg] += loop_scale;
- if (inst->dst.reladdr)
- no_spill[inst->dst.reg] = true;
+ if (inst->dst.file == VGRF) {
+ spill_costs[inst->dst.nr] += loop_scale;
+ if (inst->dst.reladdr || inst->dst.offset % REG_SIZE != 0)
+ no_spill[inst->dst.nr] = true;
}
switch (inst->opcode) {
case BRW_OPCODE_DO:
- loop_scale *= 10;
- break;
+ loop_scale *= 10;
+ break;
case BRW_OPCODE_WHILE:
- loop_scale /= 10;
- break;
+ loop_scale /= 10;
+ break;
case SHADER_OPCODE_GEN4_SCRATCH_READ:
case SHADER_OPCODE_GEN4_SCRATCH_WRITE:
for (int i = 0; i < 3; i++) {
- if (inst->src[i].file == GRF)
- no_spill[inst->src[i].reg] = true;
+ if (inst->src[i].file == VGRF)
+ no_spill[inst->src[i].nr] = true;
}
- if (inst->dst.file == GRF)
- no_spill[inst->dst.reg] = true;
- break;
+ if (inst->dst.file == VGRF)
+ no_spill[inst->dst.nr] = true;
+ break;
default:
- break;
+ break;
}
}
}
unsigned int spill_offset = last_scratch++;
/* Generate spill/unspill instructions for the objects being spilled. */
+ int scratch_reg = -1;
foreach_block_and_inst(block, vec4_instruction, inst, cfg) {
for (unsigned int i = 0; i < 3; i++) {
- if (inst->src[i].file == GRF && inst->src[i].reg == spill_reg_nr) {
- src_reg spill_reg = inst->src[i];
- inst->src[i].reg = alloc.allocate(1);
- dst_reg temp = dst_reg(inst->src[i]);
-
- emit_scratch_read(block, inst, temp, spill_reg, spill_offset);
+ if (inst->src[i].file == VGRF && inst->src[i].nr == spill_reg_nr) {
+ if (scratch_reg == -1 ||
+ !can_use_scratch_for_source(inst, i, scratch_reg)) {
+ /* We need to unspill anyway so make sure we read the full vec4
+ * in any case. This way, the cached register can be reused
+ * for consecutive instructions that read different channels of
+ * the same vec4.
+ */
+ scratch_reg = alloc.allocate(1);
+ src_reg temp = inst->src[i];
+ temp.nr = scratch_reg;
+ temp.swizzle = BRW_SWIZZLE_XYZW;
+ emit_scratch_read(block, inst,
+ dst_reg(temp), inst->src[i], spill_offset);
+ }
+ assert(scratch_reg != -1);
+ inst->src[i].nr = scratch_reg;
}
}
- if (inst->dst.file == GRF && inst->dst.reg == spill_reg_nr) {
+ if (inst->dst.file == VGRF && inst->dst.nr == spill_reg_nr) {
emit_scratch_write(block, inst, spill_offset);
+ scratch_reg = inst->dst.nr;
}
}
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