KonstantinSeurer
/
mesa
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

i965: Handle CMP.nz ... 0 and MOV.nz similarly in cmod propagation. 

"MOV.nz null src" and "CMP.nz null src 0" are equivalent instructions.

Previously, we deleted MOV.nz instructions when the instruction
generating the MOV's source also wrote the flag register (as the flag
register already contains the desired value).  However, we wouldn't
delete CMP.nz instructions that served the same purpose.

We also didn't attempt true cmod propagation on MOV.nz instructions,
while we would for the equivalent CMP.nz form.

This patch fixes both limitations, treating both forms equally.
CMP.nz instructions will now be deleted (helping the NIR backend),
and MOV.nz instructions will have their .nz propagated.

No changes in shader-db without NIR.  With NIR,

total instructions in shared programs: 6006153 -> 5969364 (-0.61%)
instructions in affected programs:     2087139 -> 2050350 (-1.76%)
helped:                                10704
HURT:                                  0
GAINED:                                2
LOST:                                  2

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
This commit is contained in:
Kenneth Graunke 2015-01-24 04:16:54 -08:00
parent 9cbb9165b9
commit 9f5fee8804
1 changed files with 10 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
src/mesa/drivers/dri/i965/brw_fs_cmod_propagation.cpp
View File

@ -69,8 +69,7 @@ opt_cmod_propagation_local(fs_visitor *v, bblock_t *block)
continue;
if (inst->opcode == BRW_OPCODE_MOV &&
(inst->conditional_mod != BRW_CONDITIONAL_NZ ||
inst->src[0].negate))
inst->conditional_mod != BRW_CONDITIONAL_NZ)
continue;
bool read_flag = false;
@ -81,15 +80,20 @@ opt_cmod_propagation_local(fs_visitor *v, bblock_t *block)
scan_inst->dst.reg_offset != inst->src[0].reg_offset)
break;
if (inst->opcode == BRW_OPCODE_MOV) {
if (!scan_inst->writes_flag())
break;
/* If the instruction generating inst's source also wrote the
* flag, and inst is doing a simple .nz comparison, then inst
* is redundant - the appropriate value is already in the flag
* register. Delete inst.
*/
if (inst->conditional_mod == BRW_CONDITIONAL_NZ &&
!inst->src[0].negate &&
scan_inst->writes_flag()) {
inst->remove(block);
progress = true;
break;
}
/* Otherwise, try propagating the conditional. */
enum brw_conditional_mod cond =
inst->src[0].negate ? brw_swap_cmod(inst->conditional_mod)
: inst->conditional_mod;