Mesa (main): nir: fix GCM when GVN enabled

[GitLab Mirror]

Module: Mesa
Branch: main
Commit: edfcc4f0227322fd8f2d72fcf68c96e23b52ba01
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=edfcc4f0227322fd8f2d72fcf68c96e23b52ba01

Author: Timothy Arceri <tarceri at itsqueeze.com>
Date:   Fri Aug  6 23:39:06 2021 +1000

nir: fix GCM when GVN enabled

Enabling GVN uncovered a bug where we would crash if the pass
thinking about pushing something into a loop.

Fixes: 6538b3e56614 ("nir: add heuristic for instructions in loops with GCM")

Acked-by: Timur Kristóf <timur.kristof at gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12242>

---

 src/compiler/nir/nir_opt_gcm.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/compiler/nir/nir_opt_gcm.c b/src/compiler/nir/nir_opt_gcm.c
index f7d46a701ee..853b630b224 100644
--- a/src/compiler/nir/nir_opt_gcm.c
+++ b/src/compiler/nir/nir_opt_gcm.c
@@ -395,6 +395,13 @@ static bool
 set_block_for_loop_instr(struct gcm_state *state, nir_instr *instr,
                          nir_block *block)
 {
+   /* If the instruction wasn't in a loop to begin with we don't want to push
+    * it down into one.
+    */
+   nir_loop *loop = state->blocks[instr->block->index].loop;
+   if (loop == NULL)
+      return true;
+
    if (nir_block_dominates(instr->block, block))
       return true;
 
@@ -402,7 +409,6 @@ set_block_for_loop_instr(struct gcm_state *state, nir_instr *instr,
     *    do{ ... break; } while(true)
     * Don't move the instruction as it will not help anything.
     */
-   nir_loop *loop = state->blocks[instr->block->index].loop;
    if (loop->info->limiting_terminator == NULL && !loop->info->complex_loop &&
        nir_block_ends_in_break(nir_loop_last_block(loop)))
       return false;