Mesa (staging/19.1): nir: Don't infinitely recurse in lower_ssa_defs_to_regs_block
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Mon Sep 9 11:31:42 UTC 2019
Module: Mesa
Branch: staging/19.1
Commit: 01d452de585560868359729ca459437298789485
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=01d452de585560868359729ca459437298789485
Author: Jason Ekstrand <jason at jlekstrand.net>
Date: Fri Aug 30 13:55:02 2019 -0500
nir: Don't infinitely recurse in lower_ssa_defs_to_regs_block
Cc: mesa-stable at lists.freedesktop.org
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira at intel.com>
(cherry picked from commit 517142252f0c63189293c7176efbf490b7ae95ea)
[Juan A. Suarez: resolve trivial conflicts]
Signed-off-by: Juan A. Suarez Romero <jasuarez at igalia.com>
Conflicts:
src/compiler/nir/nir_from_ssa.c
---
src/compiler/nir/nir_from_ssa.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/src/compiler/nir/nir_from_ssa.c b/src/compiler/nir/nir_from_ssa.c
index 99cfe757477..f0d868c38d4 100644
--- a/src/compiler/nir/nir_from_ssa.c
+++ b/src/compiler/nir/nir_from_ssa.c
@@ -827,7 +827,7 @@ nir_convert_from_ssa(nir_shader *shader, bool phi_webs_only)
static void
place_phi_read(nir_shader *shader, nir_register *reg,
- nir_ssa_def *def, nir_block *block)
+ nir_ssa_def *def, nir_block *block, unsigned depth)
{
if (block != def->parent_instr->block) {
/* Try to go up the single-successor tree */
@@ -840,14 +840,24 @@ place_phi_read(nir_shader *shader, nir_register *reg,
}
}
- if (all_single_successors) {
+ if (all_single_successors && depth < 32) {
/* All predecessors of this block have exactly one successor and it
* is this block so they must eventually lead here without
* intersecting each other. Place the reads in the predecessors
* instead of this block.
+ *
+ * We only let this function recurse 32 times because it can recurse
+ * indefinitely in the presence of infinite loops. Because we're
+ * crawling a single-successor chain, it doesn't matter where we
+ * place it so it's ok to stop at an arbitrary distance.
+ *
+ * TODO: One day, we could detect back edges and avoid the recursion
+ * that way.
*/
- set_foreach(block->predecessors, entry)
- place_phi_read(shader, reg, def, (nir_block *)entry->key);
+ set_foreach(block->predecessors, entry) {
+ place_phi_read(shader, reg, def, (nir_block *)entry->key,
+ depth + 1);
+ }
return;
}
}
@@ -904,7 +914,7 @@ nir_lower_phis_to_regs_block(nir_block *block)
assert(src->src.is_ssa);
/* We don't want derefs ending up in phi sources */
assert(!nir_src_as_deref(src->src));
- place_phi_read(shader, reg, src->src.ssa, src->pred);
+ place_phi_read(shader, reg, src->src.ssa, src->pred, 0);
}
nir_instr_remove(&phi->instr);
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