nir: allow reordering of loads from read-only modes

fossil-db (Navi):
Totals from 710 (0.51% of 138917) affected shaders:
SGPRs: 45007 -> 44791 (-0.48%)
VGPRs: 36116 -> 36284 (+0.47%); split: -0.03%, +0.50%
CodeSize: 3811540 -> 3795332 (-0.43%); split: -0.43%, +0.00%
MaxWaves: 8018 -> 8005 (-0.16%)
Instrs: 758383 -> 755084 (-0.44%); split: -0.44%, +0.01%
Cycles: 5786240 -> 5758848 (-0.47%); split: -0.48%, +0.00%

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7600>

diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 9529972..7cf6a85 100644 (file)
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2161,11 +2161,14 @@ void nir_rewrite_image_intrinsic(nir_intrinsic_instr *instr,
 static inline bool
 nir_intrinsic_can_reorder(nir_intrinsic_instr *instr)
 {
-   if (instr->intrinsic == nir_intrinsic_load_deref ||
-       instr->intrinsic == nir_intrinsic_load_ssbo ||
-       instr->intrinsic == nir_intrinsic_bindless_image_load ||
-       instr->intrinsic == nir_intrinsic_image_deref_load ||
-       instr->intrinsic == nir_intrinsic_image_load) {
+   if (instr->intrinsic == nir_intrinsic_load_deref) {
+      nir_deref_instr *deref = nir_src_as_deref(instr->src[0]);
+      return nir_deref_mode_is_in_set(deref, nir_var_read_only_modes) ||
+             (nir_intrinsic_access(instr) & ACCESS_CAN_REORDER);
+   } else if (instr->intrinsic == nir_intrinsic_load_ssbo ||
+              instr->intrinsic == nir_intrinsic_bindless_image_load ||
+              instr->intrinsic == nir_intrinsic_image_deref_load ||
+              instr->intrinsic == nir_intrinsic_image_load) {
       return nir_intrinsic_access(instr) & ACCESS_CAN_REORDER;
    } else {
       const nir_intrinsic_info *info =