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nir: Do not use continue block after removing it.

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Reinserting code directly before a jump means the block gets split
and merged, removing the original block and replacing it in the
process.

Hence keeping a pointer to the continue block over a reinsert
causes issues.

This code changes nir_opt_if to simply look for the new continue
block.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107275
CC: 18.1 <mesa-stable@lists.freedesktop.org>
This commit is contained in:
Bas Nieuwenhuizen
2018-07-15 01:19:17 +02:00
parent ce454d02cc
commit 8cacf38f52
1 changed files with 25 additions and 6 deletions
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31
src/compiler/nir/nir_opt_if.c
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@@ -26,6 +26,26 @@
#include "nir_control_flow.h"
#include "nir_loop_analyze.h"
/**
* Gets the single block that jumps back to the loop header. Already assumes
* there is exactly one such block.
*/
static nir_block*
find_continue_block(nir_loop *loop)
{
nir_block *header_block = nir_loop_first_block(loop);
nir_block *prev_block =
nir_cf_node_as_block(nir_cf_node_prev(&loop->cf_node));
assert(header_block->predecessors->entries == 2);
struct set_entry *pred_entry;
set_foreach(header_block->predecessors, pred_entry) {
if (pred_entry->key != prev_block)
return (nir_block*)pred_entry->key;
}
}
/**
* This optimization detects if statements at the tops of loops where the
* condition is a phi node of two constants and moves half of the if to above
@@ -97,12 +117,7 @@ opt_peel_loop_initial_if(nir_loop *loop)
if (header_block->predecessors->entries != 2)
return false;
nir_block *continue_block = NULL;
struct set_entry *pred_entry;
set_foreach(header_block->predecessors, pred_entry) {
if (pred_entry->key != prev_block)
continue_block = (void *)pred_entry->key;
}
nir_block *continue_block = find_continue_block(loop);
nir_cf_node *if_node = nir_cf_node_next(&header_block->cf_node);
if (!if_node || if_node->type != nir_cf_node_if)
@@ -193,6 +208,10 @@ opt_peel_loop_initial_if(nir_loop *loop)
nir_cf_reinsert(&tmp, nir_before_cf_node(&loop->cf_node));
nir_cf_reinsert(&header, nir_after_block_before_jump(continue_block));
/* Get continue block again as the previous reinsert might have removed the block. */
continue_block = find_continue_block(loop);
nir_cf_extract(&tmp, nir_before_cf_list(continue_list),
nir_after_cf_list(continue_list));
nir_cf_reinsert(&tmp, nir_after_block_before_jump(continue_block));