intel/fs: Always stall between the fences on Gen11+

Be conservative in Gfx11+ and always stall in a fence.  Since there are
two different fences, and shader might want to synchronize between them.

This change also brings back the original code block for the stall
between the fence and comment from the commit
b390ff35170fdc2b7f1fb1709a79d81edcd56981.

v2: (Caio)
 - Re-arrange code block.
 - Adjust comment.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/6958

Fixes: f7262462 ("intel/fs: Rework fence handling in brw_fs_nir.cpp")
Signed-off-by: Sagar Ghuge <sagar.ghuge@intel.com>
Tested-by: Mark Janes <markjanes@swizzler.org>
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20996>
(cherry picked from commit 0c083d29a55bf20a993eab82786d583403582c8c)

diff --git a/.pick_status.json b/.pick_status.json
index f9fbc6e..6bbc233 100644 (file)
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -3424,7 +3424,7 @@
         "description": "intel/fs: Always stall between the fences on Gen11+",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "f726246297e56ae0b3fac1af072f57dce16700ab"
     },

diff --git a/src/intel/compiler/brw_fs_nir.cpp b/src/intel/compiler/brw_fs_nir.cpp
index 7690774..0007f0e 100644 (file)
--- a/src/intel/compiler/brw_fs_nir.cpp
+++ b/src/intel/compiler/brw_fs_nir.cpp
@@ -4608,6 +4608,15 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr *instr
 
       assert(fence_regs_count <= ARRAY_SIZE(fence_regs));
 
+      /* Be conservative in Gen11+ and always stall in a fence.  Since
+       * there are two different fences, and shader might want to
+       * synchronize between them.
+       *
+       * TODO: Use scope and visibility information for the barriers from NIR
+       * to make a better decision on whether we need to stall.
+       */
+      bool force_stall = devinfo->ver >= 11;
+
       /* There are four cases where we want to insert a stall:
        *
        *  1. If we're a nir_intrinsic_end_invocation_interlock.  This is
@@ -4623,10 +4632,12 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr *instr
        *     scheduling barrier to keep the compiler from moving things
        *     around in an invalid way.
        *
-       *  4. On platforms with LSC.
+       *  4. On Gen11+ and platforms with LSC, we have multiple fence types,
+       *     without further information about the fence, we need to force a
+       *     stall.
        */
       if (instr->intrinsic == nir_intrinsic_end_invocation_interlock ||
-          fence_regs_count != 1 || devinfo->has_lsc) {
+          fence_regs_count != 1 || devinfo->has_lsc || force_stall) {
          ubld.exec_all().group(1, 0).emit(
             FS_OPCODE_SCHEDULING_FENCE, ubld.null_reg_ud(),
             fence_regs, fence_regs_count);