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aco: remove unreachable merge blocks

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Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28301>
This commit is contained in:
Rhys Perry 2024-03-25 14:20:05 +00:00 • committed by Marge Bot
parent 863718d62e
commit 842191e9ba
1 changed files with 14 additions and 40 deletions
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54
src/amd/compiler/aco_instruction_selection_setup.cpp
View file

@ -17,35 +17,6 @@ namespace aco {
namespace {
bool
is_loop_header_block(nir_block* block)
{
return block->cf_node.parent->type == nir_cf_node_loop &&
block == nir_loop_first_block(nir_cf_node_as_loop(block->cf_node.parent));
}
/* similar to nir_block_is_unreachable(), but does not require dominance information */
bool
is_block_reachable(nir_function_impl* impl, nir_block* known_reachable, nir_block* block)
{
if (block == nir_start_block(impl) || block == known_reachable)
return true;
/* skip loop back-edges */
if (is_loop_header_block(block)) {
nir_loop* loop = nir_cf_node_as_loop(block->cf_node.parent);
nir_block* preheader = nir_block_cf_tree_prev(nir_loop_first_block(loop));
return is_block_reachable(impl, known_reachable, preheader);
}
set_foreach (block->predecessors, entry) {
if (is_block_reachable(impl, known_reachable, (nir_block*)entry->key))
return true;
}
return false;
}
/* Check whether the given SSA def is only used by cross-lane instructions. */
bool
only_used_by_cross_lane_instrs(nir_def* ssa, bool follow_phis = true)
@ -91,25 +62,24 @@ only_used_by_cross_lane_instrs(nir_def* ssa, bool follow_phis = true)
/* If one side of a divergent IF ends in a branch and the other doesn't, we
* might have to emit the contents of the side without the branch at the merge
* block instead. This is so that we can use any SGPR live-out of the side
* without the branch without creating a linear phi in the invert or merge block. */
* without the branch without creating a linear phi in the invert or merge block.
*
* This also removes any unreachable merge blocks.
*/
bool
sanitize_if(nir_function_impl* impl, nir_if* nif)
{
// TODO: skip this if the condition is uniform and there are no divergent breaks/continues?
nir_block* then_block = nir_if_last_then_block(nif);
nir_block* else_block = nir_if_last_else_block(nif);
bool then_jump = nir_block_ends_in_jump(then_block) ||
!is_block_reachable(impl, nir_if_first_then_block(nif), then_block);
bool else_jump = nir_block_ends_in_jump(else_block) ||
!is_block_reachable(impl, nir_if_first_else_block(nif), else_block);
if (then_jump == else_jump)
bool then_jump = nir_block_ends_in_jump(then_block);
bool else_jump = nir_block_ends_in_jump(else_block);
if (!then_jump && !else_jump)
return false;
/* If the continue from block is empty then return as there is nothing to
* move.
*/
if (nir_cf_list_is_empty_block(else_jump ? &nif->then_list : &nif->else_list))
if (nir_cf_list_is_empty_block(then_jump ? &nif->else_list : &nif->then_list))
return false;
/* Even though this if statement has a jump on one side, we may still have
@ -120,9 +90,13 @@ sanitize_if(nir_function_impl* impl, nir_if* nif)
nir_opt_remove_phis_block(nir_cf_node_as_block(nir_cf_node_next(&nif->cf_node)));
/* Finally, move the continue from branch after the if-statement. */
nir_block* last_continue_from_blk = else_jump ? then_block : else_block;
nir_block* last_continue_from_blk = then_jump ? else_block : then_block;
nir_block* first_continue_from_blk =
else_jump ? nir_if_first_then_block(nif) : nir_if_first_else_block(nif);
then_jump ? nir_if_first_else_block(nif) : nir_if_first_then_block(nif);
/* We don't need to repair SSA. nir_remove_after_cf_node() replaces any uses with undef. */
if (then_jump && else_jump)
nir_remove_after_cf_node(&nif->cf_node);
nir_cf_list tmp;
nir_cf_extract(&tmp, nir_before_block(first_continue_from_blk),