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ra: Trade off some space to get time efficiency in ra_set_finalize().

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Our use of the register allocator in i965 is somewhat unusual.
Whereas most architectures would have a smaller set of registers with
fewer register classes and reuse that across compilation, we have 1,
2, and 4-register classes (usually) and a variable number up to 128
registers per compile depending on how many setup parameters and push
constants are present.  As a result, when compiling large numbers of
programs (as with glean texCombine going through ff_fragment_shader),
we spent much of our CPU time in computing the q[] array.  By keeping
a separate list of what the conflicts are for a particular reg, we
reduce glean texCombine time 17.0% +/- 2.3% (n=5).

We don't expect this optimization to be useful for 915, which will
have a constant register set, but it would be useful if we were switch
to this register allocator for Mesa IR.
This commit is contained in:
Eric Anholt 2011-01-17 18:34:43 -08:00
parent 5b58b8c579
commit 754b9c5363
1 changed files with 32 additions and 6 deletions
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38
src/mesa/program/register_allocate.c
View file

@ -40,6 +40,9 @@
struct ra_reg {
char *name;
GLboolean *conflicts;
unsigned int *conflict_list;
unsigned int conflict_list_size;
unsigned int num_conflicts;
};
struct ra_regs {
@ -100,16 +103,39 @@ ra_alloc_reg_set(unsigned int count)
for (i = 0; i < count; i++) {
regs->regs[i].conflicts = talloc_zero_array(regs->regs, GLboolean, count);
regs->regs[i].conflicts[i] = GL_TRUE;
regs->regs[i].conflict_list = talloc_array(regs->regs, unsigned int, 4);
regs->regs[i].conflict_list_size = 4;
regs->regs[i].conflict_list[0] = i;
regs->regs[i].num_conflicts = 1;
}
return regs;
}
static void
ra_add_conflict_list(struct ra_regs *regs, unsigned int r1, unsigned int r2)
{
struct ra_reg *reg1 = &regs->regs[r1];
if (reg1->conflict_list_size == reg1->num_conflicts) {
reg1->conflict_list_size *= 2;
reg1->conflict_list = talloc_realloc(regs,
reg1->conflict_list,
unsigned int,
reg1->conflict_list_size);
}
reg1->conflict_list[reg1->num_conflicts++] = r2;
reg1->conflicts[r2] = GL_TRUE;
}
void
ra_add_reg_conflict(struct ra_regs *regs, unsigned int r1, unsigned int r2)
{
regs->regs[r1].conflicts[r2] = GL_TRUE;
regs->regs[r2].conflicts[r1] = GL_TRUE;
if (!regs->regs[r1].conflicts[r2]) {
ra_add_conflict_list(regs, r1, r2);
ra_add_conflict_list(regs, r2, r1);
}
}
unsigned int
@ -160,15 +186,15 @@ ra_set_finalize(struct ra_regs *regs)
int max_conflicts = 0;
for (rc = 0; rc < regs->count; rc++) {
unsigned int rb;
int conflicts = 0;
int i;
if (!regs->classes[c]->regs[rc])
continue;
for (rb = 0; rb < regs->count; rb++) {
if (regs->classes[b]->regs[rb] &&
regs->regs[rb].conflicts[rc])
for (i = 0; i < regs->regs[rc].num_conflicts; i++) {
unsigned int rb = regs->regs[rc].conflict_list[i];
if (regs->classes[b]->regs[rb])
conflicts++;
}
max_conflicts = MAX2(max_conflicts, conflicts);