nir: Add a stub function inlining pass

[mesa.git] / src / glsl / nir / nir_opt_remove_phis.c

diff --git a/src/glsl/nir/nir_opt_remove_phis.c b/src/glsl/nir/nir_opt_remove_phis.c
index bf4a67e70eab98ec1e7161b7ef6ab1e5b6b1fbea..66d3754411507b66b0797631e258be3854bdd456 100644 (file)
--- 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);
@@ -89,6 +108,11 @@ remove_phis_impl(nir_function_impl *impl)
 
    nir_foreach_block(impl, remove_phis_block, &progress);
 
+   if (progress) {
+      nir_metadata_preserve(impl, nir_metadata_block_index |
+                                  nir_metadata_dominance);
+   }
+
    return progress;
 }