Mesa (main): nir/opt_memcpy: Add another case for function_temp

[GitLab Mirror]

Module: Mesa
Branch: main
Commit: 7c127ca0188a837b810f7269e7bb648523715c46
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=7c127ca0188a837b810f7269e7bb648523715c46

Author: Jason Ekstrand <jason.ekstrand at intel.com>
Date:   Mon Mar  1 21:25:11 2021 -0600

nir/opt_memcpy: Add another case for function_temp

Reviewed-by: Kristian H. Kristensen <hoegsberg at gmail.com>
Reviewed-by: Jason Ekstrand <jason.ekstrand at collabora.com> (1.5 years later)
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13166>

---

 src/compiler/nir/nir_opt_memcpy.c | 45 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 43 insertions(+), 2 deletions(-)

diff --git a/src/compiler/nir/nir_opt_memcpy.c b/src/compiler/nir/nir_opt_memcpy.c
index d022e5811ab..d984c131e28 100644
--- a/src/compiler/nir/nir_opt_memcpy.c
+++ b/src/compiler/nir/nir_opt_memcpy.c
@@ -123,7 +123,8 @@ type_is_tightly_packed(const struct glsl_type *type, unsigned *size_out)
 }
 
 static bool
-try_lower_memcpy(nir_builder *b, nir_intrinsic_instr *cpy)
+try_lower_memcpy(nir_builder *b, nir_intrinsic_instr *cpy,
+                 struct set *complex_vars)
 {
    nir_deref_instr *dst = nir_src_as_deref(cpy->src[0]);
    nir_deref_instr *src = nir_src_as_deref(cpy->src[1]);
@@ -192,6 +193,26 @@ try_lower_memcpy(nir_builder *b, nir_intrinsic_instr *cpy)
       return true;
    }
 
+   /* If we can get at the variable AND the only complex use of that variable
+    * is as a memcpy destination, then we don't have to care about any empty
+    * space in the variable.  In particular, we know that the variable is never
+    * cast to any other type and it's never used as a memcpy source so nothing
+    * can see any padding bytes.  This holds even if some other memcpy only
+    * writes to part of the variable.
+    */
+   if (dst->deref_type == nir_deref_type_var &&
+       dst->modes == nir_var_function_temp &&
+       _mesa_set_search(complex_vars, dst->var) == NULL &&
+       glsl_get_explicit_size(dst->type, false) <= size) {
+      b->cursor = nir_instr_remove(&cpy->instr);
+      src = nir_build_deref_cast(b, &src->dest.ssa,
+                                 src->modes, dst->type, 0);
+      nir_copy_deref_with_access(b, dst, src,
+                                 nir_intrinsic_dst_access(cpy),
+                                 nir_intrinsic_src_access(cpy));
+      return true;
+   }
+
    if (src->modes == nir_var_function_temp &&
        type_is_tightly_packed(src->type, &type_size) &&
        type_size == size) {
@@ -215,6 +236,24 @@ opt_memcpy_impl(nir_function_impl *impl)
    nir_builder b;
    nir_builder_init(&b, impl);
 
+   struct set *complex_vars = _mesa_pointer_set_create(NULL);
+
+   nir_foreach_block(block, impl) {
+      nir_foreach_instr(instr, block) {
+         if (instr->type != nir_instr_type_deref)
+            continue;
+
+         nir_deref_instr *deref = nir_instr_as_deref(instr);
+         if (deref->deref_type != nir_deref_type_var)
+            continue;
+
+         nir_deref_instr_has_complex_use_options opts =
+            nir_deref_instr_has_complex_use_allow_memcpy_dst;
+         if (nir_deref_instr_has_complex_use(deref, opts))
+            _mesa_set_add(complex_vars, deref->var);
+      }
+   }
+
    nir_foreach_block(block, impl) {
       nir_foreach_instr_safe(instr, block) {
          if (instr->type != nir_instr_type_intrinsic)
@@ -229,13 +268,15 @@ opt_memcpy_impl(nir_function_impl *impl)
          while (opt_memcpy_deref_cast(cpy, &cpy->src[1]))
             progress = true;
 
-         if (try_lower_memcpy(&b, cpy)) {
+         if (try_lower_memcpy(&b, cpy, complex_vars)) {
             progress = true;
             continue;
          }
       }
    }
 
+   _mesa_set_destroy(complex_vars, NULL);
+
    if (progress) {
       nir_metadata_preserve(impl, nir_metadata_block_index |
                                   nir_metadata_dominance);