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intel/fs: Don't delete coalesced MOVs if they have a cmod 

Shader-db results on ICL:

    total instructions in shared programs: 17133088 -> 17133287 (<.01%)
    instructions in affected programs: 61300 -> 61499 (0.32%)
    helped: 0
    HURT: 199

This means it's likely fixing 199 bugs. :-)  All the changed shaders are
in Mad Max.  It's surprisingly difficult to get the back-end compiler to
generate a pattern that hits this we don't tend to emit a lot coalescable
MOVs.  The pattern in Mad Max that's able to hit is fsign(fsat(x)) under
the right conditions.

Closes: #2820
Cc: mesa-stable@lists.freedesktop.org
Tested-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4773>
This commit is contained in:
Jason Ekstrand 2020-04-27 15:31:12 -05:00 committed by Marge Bot
parent 6fe7d6758a
commit e581ddeeee
1 changed files with 15 additions and 2 deletions
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17
src/intel/compiler/brw_fs_register_coalesce.cpp
View File

@ -277,13 +277,26 @@ fs_visitor::register_coalesce()
progress = true;
for (int i = 0; i < src_size; i++) {
if (mov[i]) {
if (!mov[i])
continue;
if (mov[i]->conditional_mod == BRW_CONDITIONAL_NONE) {
mov[i]->opcode = BRW_OPCODE_NOP;
mov[i]->conditional_mod = BRW_CONDITIONAL_NONE;
mov[i]->dst = reg_undef;
for (int j = 0; j < mov[i]->sources; j++) {
mov[i]->src[j] = reg_undef;
}
} else {
/* If we have a conditional modifier, rewrite the MOV to be a
* MOV.cmod from the coalesced register. Hopefully, cmod
* propagation will clean this up and move it to the instruction
* that writes the register. If not, this keeps things correct
* while still letting us coalesce.
*/
assert(mov[i]->opcode == BRW_OPCODE_MOV);
assert(mov[i]->sources == 1);
mov[i]->src[0] = mov[i]->dst;
mov[i]->dst = retype(brw_null_reg(), mov[i]->dst.type);
}
}