intel/fs: Only stall after sending all memory fence messages

In Gen11+, when emitting a fence for both L3 and SLM, the generated
code would look like

    SEND, MOV (for stall), SEND, MOV (for stall)

This commit change that so two SENDs are emitted before the MOVs for
stall.  This is similar to the approach used in Ivy Bridge for the
render fence.

Reviewed-by: Francisco Jerez <currojerez@riseup.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3278>

diff --git a/src/intel/compiler/brw_fs_nir.cpp b/src/intel/compiler/brw_fs_nir.cpp
index 6f415d5de827f14d0910de27b43056419d402dcd..e29ba744d8bda54b22797cd697678d5e3b4bf35f 100644 (file)
--- a/src/intel/compiler/brw_fs_nir.cpp
+++ b/src/intel/compiler/brw_fs_nir.cpp
@@ -4309,11 +4309,8 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr *instr
        * are two different fences, and shader might want to synchronize
        * between them.
        *
-       * TODO: Improve NIR so that scope and visibility information for the
-       * barriers is available here to make a better decision.
-       *
-       * TODO: When emitting more than one fence, it might help emit all
-       * the fences first and then generate the stall moves.
+       * TODO: Use scope and visibility information for the barriers from NIR
+       * to make a better decision on whether we need to stall.
        */
       const bool stall = devinfo->gen >= 11 || needs_render_fence ||
          instr->intrinsic == nir_intrinsic_end_invocation_interlock;
@@ -4321,6 +4318,9 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr *instr
       const bool commit_enable = stall ||
          devinfo->gen >= 10; /* HSD ES # 1404612949 */
 
+      unsigned fence_regs_count = 0;
+      fs_reg fence_regs[2] = {};
+
       const fs_builder ubld = bld.group(8, 0);
 
       if (l3_fence) {
@@ -4332,6 +4332,8 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr *instr
                       brw_imm_ud(/* bti */ 0));
          fence->sfid = GEN7_SFID_DATAPORT_DATA_CACHE;
 
+         fence_regs[fence_regs_count++] = fence->dst;
+
          if (needs_render_fence) {
             fs_inst *render_fence =
                ubld.emit(opcode,
@@ -4341,13 +4343,7 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr *instr
                          brw_imm_ud(/* bti */ 0));
             render_fence->sfid = GEN6_SFID_DATAPORT_RENDER_CACHE;
 
-            ubld.exec_all().group(1, 0).emit(
-               FS_OPCODE_SCHEDULING_FENCE, ubld.null_reg_ud(),
-               fence->dst, render_fence->dst);
-         } else if (stall) {
-            ubld.exec_all().group(1, 0).emit(
-               FS_OPCODE_SCHEDULING_FENCE, ubld.null_reg_ud(),
-               fence->dst);
+            fence_regs[fence_regs_count++] = render_fence->dst;
          }
       }
 
@@ -4361,15 +4357,16 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr *instr
                       brw_imm_ud(GEN7_BTI_SLM));
          fence->sfid = GEN7_SFID_DATAPORT_DATA_CACHE;
 
-         if (stall) {
-            ubld.exec_all().group(1, 0).emit(
-               FS_OPCODE_SCHEDULING_FENCE, ubld.null_reg_ud(),
-               fence->dst);
-         }
+         fence_regs[fence_regs_count++] = fence->dst;
       }
 
-      if (!l3_fence && !slm_fence)
-         ubld.emit(FS_OPCODE_SCHEDULING_FENCE);
+      assert(fence_regs_count <= 2);
+
+      if (stall || fence_regs_count == 0) {
+         ubld.exec_all().group(1, 0).emit(
+            FS_OPCODE_SCHEDULING_FENCE, ubld.null_reg_ud(),
+            fence_regs, fence_regs_count);
+      }
 
       break;
    }