diff options
| -rw-r--r-- | src/glsl/nir/nir_opt_remove_phis.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/src/glsl/nir/nir_opt_remove_phis.c b/src/glsl/nir/nir_opt_remove_phis.c index bf4a67e70ea..5bdf7ef4da7 100644 --- a/src/glsl/nir/nir_opt_remove_phis.c +++ b/src/glsl/nir/nir_opt_remove_phis.c @@ -58,6 +58,20 @@ remove_phis_block(nir_block *block, void *state) nir_foreach_phi_src(phi, src) { assert(src->src.is_ssa); + + /* For phi nodes at the beginning of loops, we may encounter some + * sources from backedges that point back to the destination of the + * same phi, i.e. something like: + * + * a = phi(a, b, ...) + * + * We can safely ignore these sources, since if all of the normal + * sources point to the same definition, then that definition must + * still dominate the phi node, and the phi will still always take + * the value of that definition. + */ + if (src->src.ssa == &phi->dest.ssa) + continue; if (def == NULL) { def = src->src.ssa; @@ -72,6 +86,11 @@ remove_phis_block(nir_block *block, void *state) if (!srcs_same) continue; + /* We must have found at least one definition, since there must be at + * least one forward edge. + */ + assert(def != NULL); + assert(phi->dest.is_ssa); nir_ssa_def_rewrite_uses(&phi->dest.ssa, nir_src_for_ssa(def)); nir_instr_remove(instr); |