remap_table[i] = new_index;
virtual_grf_sizes[new_index] = virtual_grf_sizes[i];
if (live_intervals_valid) {
- virtual_grf_use[new_index] = virtual_grf_use[i];
- virtual_grf_def[new_index] = virtual_grf_def[i];
+ virtual_grf_start[new_index] = virtual_grf_start[i];
+ virtual_grf_end[new_index] = virtual_grf_end[i];
}
++new_index;
}
}
/**
- * Must be called after calculate_live_intervales() to remove unused
- * writes to registers -- register allocation will fail otherwise
- * because something deffed but not used won't be considered to
- * interfere with other regs.
+ * Removes any instructions writing a VGRF where that VGRF is not used by any
+ * later instruction.
*/
bool
fs_visitor::dead_code_eliminate()
foreach_list_safe(node, &this->instructions) {
fs_inst *inst = (fs_inst *)node;
- if (inst->dst.file == GRF && this->virtual_grf_use[inst->dst.reg] <= pc) {
- inst->remove();
- progress = true;
+ if (inst->dst.file == GRF) {
+ assert(this->virtual_grf_end[inst->dst.reg] >= pc);
+ if (this->virtual_grf_end[inst->dst.reg] == pc) {
+ inst->remove();
+ progress = true;
+ }
}
pc++;
/* Can't compute-to-MRF this GRF if someone else was going to
* read it later.
*/
- if (this->virtual_grf_use[inst->src[0].reg] > ip)
+ if (this->virtual_grf_end[inst->src[0].reg] > ip)
continue;
/* Found a move of a GRF to a MRF. Let's see if we can go
if (this->live_intervals_valid)
return;
- int *def = ralloc_array(mem_ctx, int, num_vars);
- int *use = ralloc_array(mem_ctx, int, num_vars);
- ralloc_free(this->virtual_grf_def);
- ralloc_free(this->virtual_grf_use);
- this->virtual_grf_def = def;
- this->virtual_grf_use = use;
+ int *start = ralloc_array(mem_ctx, int, num_vars);
+ int *end = ralloc_array(mem_ctx, int, num_vars);
+ ralloc_free(this->virtual_grf_start);
+ ralloc_free(this->virtual_grf_end);
+ this->virtual_grf_start = start;
+ this->virtual_grf_end = end;
for (int i = 0; i < num_vars; i++) {
- def[i] = MAX_INSTRUCTION;
- use[i] = -1;
+ start[i] = MAX_INSTRUCTION;
+ end[i] = -1;
}
/* Start by setting up the intervals with no knowledge of control
for (unsigned int i = 0; i < 3; i++) {
if (inst->src[i].file == GRF) {
int reg = inst->src[i].reg;
-
- use[reg] = ip;
+ int end_ip = ip;
/* In most cases, a register can be written over safely by the
* same instruction that is its last use. For a single
if (dispatch_width == 16 && (inst->src[i].smear ||
(this->pixel_x.reg == reg ||
this->pixel_y.reg == reg))) {
- use[reg]++;
+ end_ip++;
}
+
+ start[reg] = MIN2(start[reg], ip);
+ end[reg] = MAX2(end[reg], end_ip);
}
}
if (inst->dst.file == GRF) {
int reg = inst->dst.reg;
- def[reg] = MIN2(def[reg], ip);
+ start[reg] = MIN2(start[reg], ip);
+ end[reg] = MAX2(end[reg], ip);
}
ip++;
for (int b = 0; b < cfg.num_blocks; b++) {
for (int i = 0; i < num_vars; i++) {
if (BITSET_TEST(livevars.bd[b].livein, i)) {
- def[i] = MIN2(def[i], cfg.blocks[b]->start_ip);
- use[i] = MAX2(use[i], cfg.blocks[b]->start_ip);
+ start[i] = MIN2(start[i], cfg.blocks[b]->start_ip);
+ end[i] = MAX2(end[i], cfg.blocks[b]->start_ip);
}
if (BITSET_TEST(livevars.bd[b].liveout, i)) {
- def[i] = MIN2(def[i], cfg.blocks[b]->end_ip);
- use[i] = MAX2(use[i], cfg.blocks[b]->end_ip);
+ start[i] = MIN2(start[i], cfg.blocks[b]->end_ip);
+ end[i] = MAX2(end[i], cfg.blocks[b]->end_ip);
}
}
}
this->live_intervals_valid = true;
-
- /* Note in the non-control-flow code above, that we only take def[] as the
- * first store, and use[] as the last use. We use this in dead code
- * elimination, to determine when a store never gets used. However, we
- * also use these arrays to answer the virtual_grf_interferes() question
- * (live interval analysis), which is used for register coalescing and
- * register allocation.
- *
- * So, there's a conflict over what the array should mean: if use[]
- * considers a def after the last use, then the dead code elimination pass
- * never does anything (and it's an important pass!). But if we don't
- * include dead code, then virtual_grf_interferes() lies and we'll do
- * horrible things like coalesce the register that is dead-code-written
- * into another register that was live across the dead write (causing the
- * use of the second register to take the dead write's source value instead
- * of the coalesced MOV's source value).
- *
- * To resolve the conflict, immediately after calculating live intervals,
- * detect dead code, nuke it, and if we changed anything, calculate again
- * before returning to the caller. Now we happen to produce def[] and
- * use[] arrays that will work for virtual_grf_interferes().
- */
- if (dead_code_eliminate())
- calculate_live_intervals();
}
bool
fs_visitor::virtual_grf_interferes(int a, int b)
{
- int a_def = this->virtual_grf_def[a], a_use = this->virtual_grf_use[a];
- int b_def = this->virtual_grf_def[b], b_use = this->virtual_grf_use[b];
-
- /* If there's dead code (def but not use), it would break our test
- * unless we consider it used.
- */
- if ((a_use == -1 && a_def != MAX_INSTRUCTION) ||
- (b_use == -1 && b_def != MAX_INSTRUCTION)) {
- return true;
- }
-
- int start = MAX2(a_def, b_def);
- int end = MIN2(a_use, b_use);
-
- return start < end;
+ return !(virtual_grf_end[a] <= virtual_grf_start[b] ||
+ virtual_grf_end[b] <= virtual_grf_start[a]);
}
projects / mesa.git / commitdiff