Mesa (staging/19.2): nir/opt_remove_phis: handle phis with no sources

[GitLab Mirror]

Module: Mesa
Branch: staging/19.2
Commit: f4faf5cbd7da4f00d9293f29d1212be91bc88314
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=f4faf5cbd7da4f00d9293f29d1212be91bc88314

Author: Rhys Perry <pendingchaos02 at gmail.com>
Date:   Mon Sep 23 14:48:22 2019 +0100

nir/opt_remove_phis: handle phis with no sources

This can happen with loops with unreachable exits which are later
optimized away.

Fixes assertion in dEQP-VK.graphicsfuzz.unreachable-loops with RADV.

Cc: mesa-stable at lists.freedesktop.org
Signed-off-by: Rhys Perry <pendingchaos02 at gmail.com>
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
(cherry picked from commit 12372d60fff676c458c7a54a934f619548337f0e)

---

 src/compiler/nir/nir_opt_remove_phis.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/compiler/nir/nir_opt_remove_phis.c b/src/compiler/nir/nir_opt_remove_phis.c
index a3186116798..36e01ff7245 100644
--- a/src/compiler/nir/nir_opt_remove_phis.c
+++ b/src/compiler/nir/nir_opt_remove_phis.c
@@ -109,12 +109,13 @@ remove_phis_block(nir_block *block, nir_builder *b)
       if (!srcs_same)
          continue;
 
-      /* We must have found at least one definition, since there must be at
-       * least one forward edge.
-       */
-      assert(def != NULL);
+      if (!def) {
+         /* In this case, the phi had no sources. So turn it into an undef. */
 
-      if (mov) {
+         b->cursor = nir_after_phis(block);
+         def = nir_ssa_undef(b, phi->dest.ssa.num_components,
+                             phi->dest.ssa.bit_size);
+      } else if (mov) {
          /* If the sources were all movs from the same source with the same
           * swizzle, then we can't just pick a random move because it may not
           * dominate the phi node. Instead, we need to emit our own move after