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i965/fs: Don't emit null MOVs in CSE.

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We'd like to CSE some instructions, like CMP, that often have null
destinations. Instead of replacing them with MOVs to null, just don't
emit the MOV.

Reviewed-by: Paul Berry <stereotype441@gmail.com>
This commit is contained in:
Matt Turner 2013-10-22 15:40:08 -07:00
parent a93d54eb68
commit 219b43c612
1 changed files with 24 additions and 16 deletions
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40
src/mesa/drivers/dri/i965/brw_fs_cse.cpp
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@ -150,7 +150,7 @@ fs_visitor::opt_cse_local(bblock_t *block, exec_list *aeb)
* If we don't have a temporary already, make one.
*/
bool no_existing_temp = entry->tmp.file == BAD_FILE;
if (no_existing_temp) {
if (no_existing_temp && !entry->generator->dst.is_null()) {
int written = entry->generator->regs_written;
fs_reg orig_dst = entry->generator->dst;
@ -171,29 +171,37 @@ fs_visitor::opt_cse_local(bblock_t *block, exec_list *aeb)
}
/* dest <- temp */
int written = inst->regs_written;
assert(written == entry->generator->regs_written);
assert(inst->dst.type == entry->tmp.type);
fs_reg dst = inst->dst;
fs_reg tmp = entry->tmp;
fs_inst *copy = NULL;
for (int i = 0; i < written; i++) {
copy = MOV(dst, tmp);
copy->force_writemask_all = inst->force_writemask_all;
inst->insert_before(copy);
if (!inst->dst.is_null()) {
int written = inst->regs_written;
assert(written == entry->generator->regs_written);
assert(inst->dst.type == entry->tmp.type);
fs_reg dst = inst->dst;
fs_reg tmp = entry->tmp;
fs_inst *copy = NULL;
for (int i = 0; i < written; i++) {
copy = MOV(dst, tmp);
copy->force_writemask_all = inst->force_writemask_all;
inst->insert_before(copy);
dst.reg_offset++;
tmp.reg_offset++;
dst.reg_offset++;
tmp.reg_offset++;
}
}
/* Set our iterator so that next time through the loop inst->next
* will get the instruction in the basic block after the one we've
* removed.
*/
fs_inst *prev = (fs_inst *)inst->prev;
inst->remove();
/* Appending an instruction may have changed our bblock end. */
if (inst == block->end) {
block->end = copy;
block->end = prev;
}
/* Continue iteration with copy->next */
inst = copy;
inst = prev;
}
}