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ir3/cp_postsched: Fixup SSA use pointer for direct reads

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There's an optimization here to sink direct (i.e. not relative) reads of
an array past unrelated direct writes. However, since each write
actually reads, modifies, and then writes again to the array, this means
that we need to read the latest updated array. The old RA used the array
id instead of the SSA information, so it didn't care, but the new RA
uses ->instr instead and ignores the array id because arrays are now SSA
so it needs to be correct.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10591>
This commit is contained in:
Connor Abbott 2021-03-22 11:30:53 +01:00 • committed by Marge Bot
parent 40a1c4ba2d
commit d28b22374c
1 changed files with 17 additions and 2 deletions
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19
src/freedreno/ir3/ir3_cp_postsched.c
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@ -43,14 +43,18 @@
* access and we care about all writes to the array (as we don't know
* which array element is read). Otherwise in the case of non-relative
* access, we only have to care about the write to the specified (>= 0)
* offset.
* offset. In this case, we update `def` to point to the last write in
* between `use` and `src` to the same array, so that `use` points to
* the correct array write.
*/
static bool
has_conflicting_write(struct ir3_instruction *src,
struct ir3_instruction *use,
struct ir3_instruction **def,
unsigned id, int offset)
{
assert(src->block == use->block);
bool last_write = true;
/* NOTE that since src and use are in the same block, src by
* definition appears in the block's instr_list before use:
@ -93,6 +97,11 @@ has_conflicting_write(struct ir3_instruction *src,
/* is write to same array element? */
if (dst->array.offset == offset)
return true;
if (last_write)
*def = instr;
last_write = false;
}
return false;
@ -143,7 +152,8 @@ instr_cp_postsched(struct ir3_instruction *mov)
if (is_meta(use))
continue;
if (has_conflicting_write(mov, use, src->array.id, offset))
struct ir3_instruction *def = src->instr;
if (has_conflicting_write(mov, use, &def, src->array.id, offset))
continue;
if (conflicts(mov->address, use->address))
@ -164,6 +174,11 @@ instr_cp_postsched(struct ir3_instruction *mov)
/* preserve (abs)/etc modifiers: */
use->regs[n + 1]-> flags |= reg->flags;
/* If we're sinking the array read past any writes, make
* sure to update it to point to the new previous write:
*/
use->regs[n + 1]->instr = def;
removed = true;
}