[Mesa-dev] [RFC v1 27/38] nir/deref: Add a deref cleanup function

[Jason Ekstrand]

Sometimes it's useful for a pass to be able to clean up its own derefs
instead of waiting for DCE.  This little helper makes it very easy.
---
 src/compiler/nir/nir.h       |  2 ++
 src/compiler/nir/nir_deref.c | 13 +++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 496b123..b99dd9b 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -1018,6 +1018,8 @@ nir_deref_instr_get_variable(nir_deref_instr *instr)
    return instr->var;
 }
 
+void nir_deref_instr_cleanup(nir_deref_instr *instr);
+
 nir_deref_var *
 nir_deref_instr_to_deref(nir_deref_instr *instr, void *mem_ctx);
 
diff --git a/src/compiler/nir/nir_deref.c b/src/compiler/nir/nir_deref.c
index bf39a12..de45358 100644
--- a/src/compiler/nir/nir_deref.c
+++ b/src/compiler/nir/nir_deref.c
@@ -72,6 +72,19 @@ nir_deref_path_finish(struct nir_deref_path *path)
       ralloc_free(path->path);
 }
 
+void
+nir_deref_instr_cleanup(nir_deref_instr *instr)
+{
+   for (nir_deref_instr *d = instr; d; d = nir_deref_instr_parent(d)) {
+      /* If anyone is using this deref, leave it alone */
+      assert(d->dest.is_ssa);
+      if (!list_empty(&d->dest.ssa.uses))
+         return;
+
+      nir_instr_remove(&d->instr);
+   }
+}
+
 nir_deref_var *
 nir_deref_instr_to_deref(nir_deref_instr *instr, void *mem_ctx)
 {
-- 
2.5.0.400.gff86faf