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ir3/cp: ir3: Prevent propagating shared regs out of loops harder

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We need to check the source of the copy, not the destination. That means
this we need to move this check inside the ifs, where we know that the
source is a copy.

Fixes: 590efd180b ("Prevent propagating shared regs out of loops")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14412>
(cherry picked from commit 09731fc79a)
This commit is contained in:
Connor Abbott 2022-01-05 19:45:55 +01:00 • committed by Eric Engestrom
parent 5be8602e4d
commit 77f9a3ada4
2 changed files with 23 additions and 12 deletions
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2
.pick_status.json
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@ -2272,7 +2272,7 @@
"description": "ir3/cp: ir3: Prevent propagating shared regs out of loops harder",
"nominated": true,
"nomination_type": 1,
"resolution": 0,
"resolution": 1,
"main_sha": null,
"because_sha": "590efd180be05817163d1b70990273b535a82afe"
},

33
src/freedreno/ir3/ir3_cp.c
View file

@ -303,6 +303,22 @@ try_swap_mad_two_srcs(struct ir3_instruction *instr, unsigned new_flags)
return valid_swap;
}
/* Values that are uniform inside a loop can become divergent outside
* it if the loop has a divergent trip count. This means that we can't
* propagate a copy of a shared to non-shared register if it would
* make the shared reg's live range extend outside of its loop. Users
* outside the loop would see the value for the thread(s) that last
* exited the loop, rather than for their own thread.
*/
static bool
is_valid_shared_copy(struct ir3_instruction *dst_instr,
struct ir3_instruction *src_instr,
struct ir3_register *src_reg)
{
return !(src_reg->flags & IR3_REG_SHARED) ||
dst_instr->block->loop_id == src_instr->block->loop_id;
}
/**
* Handle cp for a given src register. This additionally handles
* the cases of collapsing immedate/const (which replace the src
@ -316,22 +332,14 @@ reg_cp(struct ir3_cp_ctx *ctx, struct ir3_instruction *instr,
{
struct ir3_instruction *src = ssa(reg);
/* Values that are uniform inside a loop can become divergent outside
* it if the loop has a divergent trip count. This means that we can't
* propagate a copy of a shared to non-shared register if it would
* make the shared reg's live range extend outside of its loop. Users
* outside the loop would see the value for the thread(s) that last
* exited the loop, rather than for their own thread.
*/
if ((src->dsts[0]->flags & IR3_REG_SHARED) &&
src->block->loop_id != instr->block->loop_id)
return false;
if (is_eligible_mov(src, instr, true)) {
/* simple case, no immed/const/relativ, only mov's w/ ssa src: */
struct ir3_register *src_reg = src->srcs[0];
unsigned new_flags = reg->flags;
if (!is_valid_shared_copy(instr, src, src_reg))
return false;
combine_flags(&new_flags, src);
if (ir3_valid_flags(instr, n, new_flags)) {
@ -357,6 +365,9 @@ reg_cp(struct ir3_cp_ctx *ctx, struct ir3_instruction *instr,
struct ir3_register *src_reg = src->srcs[0];
unsigned new_flags = reg->flags;
if (!is_valid_shared_copy(instr, src, src_reg))
return false;
if (src_reg->flags & IR3_REG_ARRAY)
return false;