intel/fs/gen12: Introduce software scoreboard lowering pass.

Gen12+ hardware lacks the register scoreboard logic that used to
guarantee data coherency between register reads and writes in previous
generations.  This lowering pass runs after register allocation in
order to make up for it.

It works by performing global dataflow analysis in order to determine
the set of potential dependencies of every instruction in the shader,
and then inserts any required SWSB annotations and additional SYNC
instructions in order to guarantee data coherency.

v2: Drop unnecessary _safe list iteration (Caio).

v3: Temporarily workaround potential WaR hazard between FPU
    instruction and subsequent out-of-order write, pending
    clarification from the hardware team.  Drop redundant tracking of
    implicit access of acc0-1, since the hardware guarantees coherency
    of these (but not the other accumulators...).

Reviewed-by: Caio Marcelo de Oliveira Filho <[email protected]>

5 files changed, 946 insertions, 0 deletions

diff --git a/src/intel/Makefile.sources b/src/intel/Makefile.sources
index a57c0d1bada..ebe4efee992 100644
--- a/src/intel/Makefile.sources
+++ b/src/intel/Makefile.sources
@@ -68,6 +68,7 @@ COMPILER_FILES = \
 	compiler/brw_fs_reg_allocate.cpp \
 	compiler/brw_fs_register_coalesce.cpp \
 	compiler/brw_fs_saturate_propagation.cpp \
+	compiler/brw_fs_scoreboard.cpp \
 	compiler/brw_fs_sel_peephole.cpp \
 	compiler/brw_fs_validate.cpp \
 	compiler/brw_fs_visitor.cpp \
diff --git a/src/intel/compiler/brw_fs.cpp b/src/intel/compiler/brw_fs.cpp
index 30a95b419f0..337dde63848 100644
--- a/src/intel/compiler/brw_fs.cpp
+++ b/src/intel/compiler/brw_fs.cpp
@@ -3509,6 +3509,8 @@ fs_visitor::emit_repclear_shader()
       assert(mov->src[0].file == FIXED_GRF);
       mov->src[0] = brw_vec4_grf(mov->src[0].nr, 0);
    }
+
+   lower_scoreboard();
 }
 
 /**
@@ -7557,6 +7559,8 @@ fs_visitor::allocate_registers(unsigned min_dispatch_width, bool allow_spilling)
        */
       assert(prog_data->total_scratch < max_scratch_size);
    }
+
+   lower_scoreboard();
 }
 
 bool
diff --git a/src/intel/compiler/brw_fs.h b/src/intel/compiler/brw_fs.h
index 4d5cdd0c013..ede5b0a701c 100644
--- a/src/intel/compiler/brw_fs.h
+++ b/src/intel/compiler/brw_fs.h
@@ -167,6 +167,7 @@ public:
    bool lower_integer_multiplication();
    bool lower_minmax();
    bool lower_simd_width();
+   bool lower_scoreboard();
    bool opt_combine_constants();
 
    void emit_dummy_fs();
diff --git a/src/intel/compiler/brw_fs_scoreboard.cpp b/src/intel/compiler/brw_fs_scoreboard.cpp
new file mode 100644
index 00000000000..f05a150e00f
--- /dev/null
+++ b/src/intel/compiler/brw_fs_scoreboard.cpp
@@ -0,0 +1,939 @@
+/*
+ * Copyright © 2019 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+/** @file brw_fs_scoreboard.cpp
+ *
+ * Gen12+ hardware lacks the register scoreboard logic that used to guarantee
+ * data coherency between register reads and writes in previous generations.
+ * This lowering pass runs after register allocation in order to make up for
+ * it.
+ *
+ * It works by performing global dataflow analysis in order to determine the
+ * set of potential dependencies of every instruction in the shader, and then
+ * inserts any required SWSB annotations and additional SYNC instructions in
+ * order to guarantee data coherency.
+ *
+ * WARNING - Access of the following (rarely used) ARF registers is not
+ *           tracked here, and require the RegDist SWSB annotation to be set
+ *           to 1 by the generator in order to avoid data races:
+ *
+ *  - sp stack pointer
+ *  - sr0 state register
+ *  - cr0 control register
+ *  - ip instruction pointer
+ *  - tm0 timestamp register
+ *  - dbg0 debug register
+ *
+ * The following ARF registers don't need to be tracked here because data
+ * coherency is still provided transparently by the hardware:
+ *
+ *  - f0-1 flag registers
+ *  - n0 notification register
+ *  - tdr0 thread dependency register
+ */
+
+#include <tuple>
+#include <vector>
+
+#include "brw_fs.h"
+#include "brw_cfg.h"
+
+using namespace brw;
+
+namespace {
+   /**
+    * In-order instruction accounting.
+    * @{
+    */
+
+   /**
+    * Number of in-order hardware instructions contained in this IR
+    * instruction.  This determines the increment applied to the RegDist
+    * counter calculated for any ordered dependency that crosses this
+    * instruction.
+    */
+   unsigned
+   ordered_unit(const fs_inst *inst)
+   {
+      switch (inst->opcode) {
+      case BRW_OPCODE_SYNC:
+      case BRW_OPCODE_DO:
+      case SHADER_OPCODE_UNDEF:
+      case FS_OPCODE_PLACEHOLDER_HALT:
+         return 0;
+      default:
+         /* Note that the following is inaccurate for virtual instructions
+          * that expand to more in-order instructions than assumed here, but
+          * that can only lead to suboptimal execution ordering, data
+          * coherency won't be impacted.  Providing exact RegDist counts for
+          * each virtual instruction would allow better ALU performance, but
+          * it would require keeping this switch statement in perfect sync
+          * with the generator in order to avoid data corruption.  Lesson is
+          * (again) don't use virtual instructions if you want optimal
+          * scheduling.
+          */
+         return is_unordered(inst) ? 0 : 1;
+      }
+   }
+
+   /**
+    * Type for an instruction counter that increments for in-order
+    * instructions only, arbitrarily denoted 'jp' throughout this lowering
+    * pass in order to distinguish it from the regular instruction counter.
+    */
+   typedef int ordered_address;
+
+   /**
+    * Calculate the local ordered_address instruction counter at every
+    * instruction of the shader for subsequent constant-time look-up.
+    */
+   std::vector<ordered_address>
+   ordered_inst_addresses(const fs_visitor *shader)
+   {
+      std::vector<ordered_address> jps;
+      ordered_address jp = 0;
+
+      foreach_block_and_inst(block, fs_inst, inst, shader->cfg) {
+         jps.push_back(jp);
+         jp += ordered_unit(inst);
+      }
+
+      return jps;
+   }
+
+   /**
+    * Synchronization mode required for data manipulated by in-order
+    * instructions.
+    *
+    * Similar to tgl_sbid_mode, but without SET mode.  Defined as a separate
+    * enum for additional type safety.  The hardware doesn't provide control
+    * over the synchronization mode for RegDist annotations, this is only used
+    * internally in this pass in order to optimize out redundant read
+    * dependencies where possible.
+    */
+   enum tgl_regdist_mode {
+      TGL_REGDIST_NULL = 0,
+      TGL_REGDIST_SRC = 1,
+      TGL_REGDIST_DST = 2
+   };
+
+   /**
+    * Allow bitwise arithmetic of tgl_regdist_mode enums.
+    */
+   tgl_regdist_mode
+   operator|(tgl_regdist_mode x, tgl_regdist_mode y)
+   {
+      return tgl_regdist_mode(unsigned(x) | unsigned(y));
+   }
+
+   tgl_regdist_mode
+   operator&(tgl_regdist_mode x, tgl_regdist_mode y)
+   {
+      return tgl_regdist_mode(unsigned(x) & unsigned(y));
+   }
+
+   tgl_regdist_mode &
+   operator|=(tgl_regdist_mode &x, tgl_regdist_mode y)
+   {
+      return x = x | y;
+   }
+
+   tgl_regdist_mode &
+   operator&=(tgl_regdist_mode &x, tgl_regdist_mode y)
+   {
+      return x = x & y;
+   }
+
+   /** @} */
+
+   /**
+    * Representation of an equivalence relation among the set of unsigned
+    * integers.
+    *
+    * Its initial state is the identity relation '~' such that i ~ j if and
+    * only if i == j for every pair of unsigned integers i and j.
+    */
+   struct equivalence_relation {
+      /**
+       * Return equivalence class index of the specified element.  Effectively
+       * this is the numeric value of an arbitrary representative from the
+       * equivalence class.
+       *
+       * Allows the evaluation of the equivalence relation according to the
+       * rule that i ~ j if and only if lookup(i) == lookup(j).
+       */
+      unsigned
+      lookup(unsigned i) const
+      {
+         if (i < is.size() && is[i] != i)
+            return lookup(is[i]);
+         else
+            return i;
+      }
+
+      /**
+       * Create an array with the results of the lookup() method for
+       * constant-time evaluation.
+       */
+      std::vector<unsigned>
+      flatten() const {
+         std::vector<unsigned> ids;
+
+         for (const auto i : is)
+            ids.push_back(lookup(i));
+
+         return ids;
+      }
+
+      /**
+       * Mutate the existing equivalence relation minimally by imposing the
+       * additional requirement that i ~ j.
+       *
+       * The algorithm updates the internal representation recursively in
+       * order to guarantee transitivity while preserving the previously
+       * specified equivalence requirements.
+       */
+      unsigned
+      link(unsigned i, unsigned j)
+      {
+         const unsigned k = lookup(i);
+         assign(i, k);
+         assign(j, k);
+         return k;
+      }
+
+   private:
+      /**
+       * Assign the representative of \p from to be equivalent to \p to.
+       *
+       * At the same time the data structure is partially flattened as much as
+       * it's possible without increasing the number of recursive calls.
+       */
+      void
+      assign(unsigned from, unsigned to)
+      {
+         if (from != to) {
+            if (from < is.size() && is[from] != from)
+               assign(is[from], to);
+
+            for (unsigned i = is.size(); i <= from; i++)
+               is.push_back(i);
+
+            is[from] = to;
+         }
+      }
+
+      std::vector<unsigned> is;
+   };
+
+   /**
+    * Representation of a data dependency between two instructions in the
+    * program.
+    * @{
+    */
+   struct dependency {
+      /**
+       * No dependency information.
+       */
+      dependency() : ordered(TGL_REGDIST_NULL), jp(INT_MIN),
+                     unordered(TGL_SBID_NULL), id(0) {}
+
+      /**
+       * Construct a dependency on the in-order instruction with the provided
+       * ordered_address instruction counter.
+       */
+      dependency(tgl_regdist_mode mode, ordered_address jp) :
+         ordered(mode), jp(jp), unordered(TGL_SBID_NULL), id(0) {}
+
+      /**
+       * Construct a dependency on the out-of-order instruction with the
+       * specified synchronization token.
+       */
+      dependency(tgl_sbid_mode mode, unsigned id) :
+         ordered(TGL_REGDIST_NULL), jp(INT_MIN), unordered(mode), id(id) {}
+
+      /**
+       * Synchronization mode of in-order dependency, or zero if no in-order
+       * dependency is present.
+       */
+      tgl_regdist_mode ordered;
+
+      /**
+       * Instruction counter of in-order dependency.
+       *
+       * For a dependency part of a different block in the program, this is
+       * relative to the specific control flow path taken between the
+       * dependency and the current block: It is the ordered_address such that
+       * the difference between it and the ordered_address of the first
+       * instruction of the current block is exactly the number of in-order
+       * instructions across that control flow path.  It is not guaranteed to
+       * be equal to the local ordered_address of the generating instruction
+       * [as returned by ordered_inst_addresses()], except for block-local
+       * dependencies.
+       */
+      ordered_address jp;
+
+      /**
+       * Synchronization mode of unordered dependency, or zero if no unordered
+       * dependency is present.
+       */
+      tgl_sbid_mode unordered;
+
+      /** Synchronization token of out-of-order dependency. */
+      unsigned id;
+
+      /**
+       * Trivial in-order dependency that's always satisfied.
+       *
+       * Note that unlike a default-constructed dependency() which is also
+       * trivially satisfied, this is considered to provide dependency
+       * information and can be used to clear a previously pending dependency
+       * via shadow().
+       */
+      static const dependency done;
+
+      friend bool
+      operator==(const dependency &dep0, const dependency &dep1)
+      {
+         return dep0.ordered == dep1.ordered &&
+                dep0.jp == dep1.jp &&
+                dep0.unordered == dep1.unordered &&
+                dep0.id == dep1.id;
+      }
+
+      friend bool
+      operator!=(const dependency &dep0, const dependency &dep1)
+      {
+         return !(dep0 == dep1);
+      }
+   };
+
+   const dependency dependency::done = dependency(TGL_REGDIST_SRC, INT_MIN);
+
+   /**
+    * Return whether \p dep contains any dependency information.
+    */
+   bool
+   is_valid(const dependency &dep)
+   {
+      return dep.ordered || dep.unordered;
+   }
+
+   /**
+    * Combine \p dep0 and \p dep1 into a single dependency object that is only
+    * satisfied when both original dependencies are satisfied.  This might
+    * involve updating the equivalence relation \p eq in order to make sure
+    * that both out-of-order dependencies are assigned the same hardware SBID
+    * as synchronization token.
+    */
+   dependency
+   merge(equivalence_relation &eq,
+         const dependency &dep0, const dependency &dep1)
+   {
+      dependency dep;
+
+      if (dep0.ordered || dep1.ordered) {
+         dep.ordered = dep0.ordered | dep1.ordered;
+         dep.jp = MAX2(dep0.jp, dep1.jp);
+      }
+
+      if (dep0.unordered || dep1.unordered) {
+         dep.unordered = dep0.unordered | dep1.unordered;
+         dep.id = eq.link(dep0.unordered ? dep0.id : dep1.id,
+                          dep1.unordered ? dep1.id : dep0.id);
+      }
+
+      return dep;
+   }
+
+   /**
+    * Override dependency information of \p dep0 with that of \p dep1.
+    */
+   dependency
+   shadow(const dependency &dep0, const dependency &dep1)
+   {
+      return is_valid(dep1) ? dep1 : dep0;
+   }
+
+   /**
+    * Translate dependency information across the program.
+    *
+    * This returns a dependency on the same instruction translated to the
+    * ordered_address space of a different block.  The correct shift for
+    * transporting a dependency across an edge of the CFG is the difference
+    * between the local ordered_address of the first instruction of the target
+    * block and the local ordered_address of the instruction immediately after
+    * the end of the origin block.
+    */
+   dependency
+   transport(dependency dep, int delta)
+   {
+      if (dep.ordered && dep.jp > INT_MIN)
+         dep.jp += delta;
+
+      return dep;
+   }
+
+   /**
+    * Return simplified dependency removing any synchronization modes not
+    * applicable to an instruction reading the same register location.
+    */
+   dependency
+   dependency_for_read(dependency dep)
+   {
+      dep.ordered &= TGL_REGDIST_DST;
+      return dep;
+   }
+
+   /**
+    * Return simplified dependency removing any synchronization modes not
+    * applicable to an instruction \p inst writing the same register location.
+    */
+   dependency
+   dependency_for_write(const fs_inst *inst, dependency dep)
+   {
+      if (!is_unordered(inst))
+         dep.ordered &= TGL_REGDIST_DST;
+      return dep;
+   }
+
+   /** @} */
+
+   /**
+    * Scoreboard representation.  This keeps track of the data dependencies of
+    * registers with GRF granularity.
+    */
+   class scoreboard {
+   public:
+      /**
+       * Look up the most current data dependency for register \p r.
+       */
+      dependency
+      get(const fs_reg &r) const
+      {
+         if (const dependency *p = const_cast<scoreboard *>(this)->dep(r))
+            return *p;
+         else
+            return dependency();
+      }
+
+      /**
+       * Specify the most current data dependency for register \p r.
+       */
+      void
+      set(const fs_reg &r, const dependency &d)
+      {
+         if (dependency *p = dep(r))
+            *p = d;
+      }
+
+      /**
+       * Component-wise merge() of corresponding dependencies from two
+       * scoreboard objects.  \sa merge().
+       */
+      friend scoreboard
+      merge(equivalence_relation &eq,
+            const scoreboard &sb0, const scoreboard &sb1)
+      {
+         scoreboard sb;
+
+         for (unsigned i = 0; i < ARRAY_SIZE(sb.grf_deps); i++)
+            sb.grf_deps[i] = merge(eq, sb0.grf_deps[i], sb1.grf_deps[i]);
+
+         sb.addr_dep = merge(eq, sb0.addr_dep, sb1.addr_dep);
+
+         for (unsigned i = 0; i < ARRAY_SIZE(sb.accum_deps); i++)
+            sb.accum_deps[i] = merge(eq, sb0.accum_deps[i], sb1.accum_deps[i]);
+
+         return sb;
+      }
+
+      /**
+       * Component-wise shadow() of corresponding dependencies from two
+       * scoreboard objects.  \sa shadow().
+       */
+      friend scoreboard
+      shadow(const scoreboard &sb0, const scoreboard &sb1)
+      {
+         scoreboard sb;
+
+         for (unsigned i = 0; i < ARRAY_SIZE(sb.grf_deps); i++)
+            sb.grf_deps[i] = shadow(sb0.grf_deps[i], sb1.grf_deps[i]);
+
+         sb.addr_dep = shadow(sb0.addr_dep, sb1.addr_dep);
+
+         for (unsigned i = 0; i < ARRAY_SIZE(sb.accum_deps); i++)
+            sb.accum_deps[i] = shadow(sb0.accum_deps[i], sb1.accum_deps[i]);
+
+         return sb;
+      }
+
+      /**
+       * Component-wise transport() of dependencies from a scoreboard
+       * object.  \sa transport().
+       */
+      friend scoreboard
+      transport(const scoreboard &sb0, int delta)
+      {
+         scoreboard sb;
+
+         for (unsigned i = 0; i < ARRAY_SIZE(sb.grf_deps); i++)
+            sb.grf_deps[i] = transport(sb0.grf_deps[i], delta);
+
+         sb.addr_dep = transport(sb0.addr_dep, delta);
+
+         for (unsigned i = 0; i < ARRAY_SIZE(sb.accum_deps); i++)
+            sb.accum_deps[i] = transport(sb0.accum_deps[i], delta);
+
+         return sb;
+      }
+
+      friend bool
+      operator==(const scoreboard &sb0, const scoreboard &sb1)
+      {
+         for (unsigned i = 0; i < ARRAY_SIZE(sb0.grf_deps); i++) {
+            if (sb0.grf_deps[i] != sb1.grf_deps[i])
+               return false;
+         }
+
+         if (sb0.addr_dep != sb1.addr_dep)
+            return false;
+
+         for (unsigned i = 0; i < ARRAY_SIZE(sb0.accum_deps); i++) {
+            if (sb0.accum_deps[i] != sb1.accum_deps[i])
+               return false;
+         }
+
+         return true;
+      }
+
+      friend bool
+      operator!=(const scoreboard &sb0, const scoreboard &sb1)
+      {
+         return !(sb0 == sb1);
+      }
+
+   private:
+      dependency grf_deps[BRW_MAX_GRF];
+      dependency addr_dep;
+      dependency accum_deps[10];
+
+      dependency *
+      dep(const fs_reg &r)
+      {
+         const unsigned reg = (r.file == VGRF ? r.nr + r.offset / REG_SIZE :
+                               reg_offset(r) / REG_SIZE);
+
+         return (r.file == VGRF || r.file == FIXED_GRF ? &grf_deps[reg] :
+                 r.file == MRF ? &grf_deps[GEN7_MRF_HACK_START + reg] :
+                 r.file == ARF && reg >= BRW_ARF_ADDRESS &&
+                                  reg < BRW_ARF_ACCUMULATOR ? &addr_dep :
+                 r.file == ARF && reg >= BRW_ARF_ACCUMULATOR &&
+                                  reg < BRW_ARF_FLAG ? &accum_deps[
+                                     reg - BRW_ARF_ACCUMULATOR] :
+                 NULL);
+      }
+   };
+
+   /**
+    * Dependency list handling.
+    * @{
+    */
+
+   /**
+    * Add dependency \p dep to the list of dependencies of an instruction
+    * \p deps.
+    */
+   void
+   add_dependency(const std::vector<unsigned> &ids,
+                  std::vector<dependency> &deps, dependency dep)
+   {
+      if (is_valid(dep)) {
+         /* Translate the unordered dependency token first in order to keep
+          * the list minimally redundant.
+          */
+         if (dep.unordered && dep.id < ids.size())
+            dep.id = ids[dep.id];
+
+         /* Try to combine the specified dependency with any existing ones. */
+         for (auto &dep1 : deps) {
+            if (dep.ordered && dep1.ordered) {
+               dep1.jp = MAX2(dep1.jp, dep.jp);
+               dep1.ordered |= dep.ordered;
+               dep.ordered = TGL_REGDIST_NULL;
+            }
+
+            if (dep.unordered && dep1.unordered && dep1.id == dep.id) {
+               dep1.unordered |= dep.unordered;
+               dep.unordered = TGL_SBID_NULL;
+            }
+         }
+
+         /* Add it to the end of the list if necessary. */
+         if (is_valid(dep))
+            deps.push_back(dep);
+      }
+   }
+
+   /**
+    * Construct a tgl_swsb annotation encoding any ordered dependencies from
+    * the dependency list \p deps of an instruction with ordered_address
+    * \p jp.
+    */
+   tgl_swsb
+   ordered_dependency_swsb(const std::vector<dependency> &deps,
+                           const ordered_address &jp)
+   {
+      unsigned min_dist = ~0u;
+
+      for (const auto &dep : deps) {
+         if (dep.ordered) {
+            const unsigned dist = jp - dep.jp;
+            const unsigned max_dist = 10;
+            assert(jp > dep.jp);
+            if (dist <= max_dist)
+               min_dist = MIN3(min_dist, dist, 7);
+         }
+      }
+
+      return { min_dist == ~0u ? 0 : min_dist };
+   }
+
+   /**
+    * Return whether the dependency list \p deps of an instruction with
+    * ordered_address \p jp has any non-trivial ordered dependencies.
+    */
+   bool
+   find_ordered_dependency(const std::vector<dependency> &deps,
+                           const ordered_address &jp)
+   {
+      return ordered_dependency_swsb(deps, jp).regdist;
+   }
+
+   /**
+    * Return the full tgl_sbid_mode bitset for the first unordered dependency
+    * on the list \p deps that matches the specified tgl_sbid_mode, or zero if
+    * no such dependency is present.
+    */
+   tgl_sbid_mode
+   find_unordered_dependency(const std::vector<dependency> &deps,
+                             tgl_sbid_mode unordered)
+   {
+      if (unordered) {
+         for (const auto &dep : deps) {
+            if (unordered & dep.unordered)
+               return dep.unordered;
+         }
+      }
+
+      return TGL_SBID_NULL;
+   }
+
+   /**
+    * Return the tgl_sbid_mode bitset of an unordered dependency from the list
+    * \p deps that can be represented directly in the SWSB annotation of the
+    * instruction without additional SYNC instructions, or zero if no such
+    * dependency is present.
+    */
+   tgl_sbid_mode
+   baked_unordered_dependency_mode(const fs_inst *inst,
+                                   const std::vector<dependency> &deps,
+                                   const ordered_address &jp)
+   {
+      const bool has_ordered = find_ordered_dependency(deps, jp);
+
+      if (find_unordered_dependency(deps, TGL_SBID_SET))
+         return find_unordered_dependency(deps, TGL_SBID_SET);
+      else if (has_ordered && is_unordered(inst))
+         return TGL_SBID_NULL;
+      else if (find_unordered_dependency(deps, TGL_SBID_DST) &&
+               (!has_ordered || !is_unordered(inst)))
+         return find_unordered_dependency(deps, TGL_SBID_DST);
+      else if (!has_ordered)
+         return find_unordered_dependency(deps, TGL_SBID_SRC);
+      else
+         return TGL_SBID_NULL;
+   }
+
+   /** @} */
+
+   /**
+    * Shader instruction dependency calculation.
+    * @{
+    */
+
+   /**
+    * Update scoreboard object \p sb to account for the execution of
+    * instruction \p inst.
+    */
+   void
+   update_inst_scoreboard(const fs_visitor *shader,
+                          const std::vector<ordered_address> &jps,
+                          const fs_inst *inst, unsigned ip, scoreboard &sb)
+   {
+      /* Track any source registers that may be fetched asynchronously by this
+       * instruction, otherwise clear the dependency in order to avoid
+       * subsequent redundant synchronization.
+       */
+      for (unsigned i = 0; i < inst->sources; i++) {
+         const dependency rd_dep =
+            inst->is_payload(i) || inst->is_math() ? dependency(TGL_SBID_SRC, ip) :
+            ordered_unit(inst) ? dependency(TGL_REGDIST_SRC, jps[ip]) :
+            dependency::done;
+
+         for (unsigned j = 0; j < regs_read(inst, i); j++)
+            sb.set(byte_offset(inst->src[i], REG_SIZE * j), rd_dep);
+      }
+
+      if (is_send(inst) && inst->base_mrf != -1) {
+         const dependency rd_dep = dependency(TGL_SBID_SRC, ip);
+
+         for (unsigned j = 0; j < inst->mlen; j++)
+            sb.set(brw_uvec_mrf(8, inst->base_mrf + j, 0), rd_dep);
+      }
+
+      /* Track any destination registers of this instruction. */
+      const dependency wr_dep =
+         is_unordered(inst) ? dependency(TGL_SBID_DST, ip) :
+         ordered_unit(inst) ? dependency(TGL_REGDIST_DST, jps[ip]) :
+         dependency();
+
+      if (is_valid(wr_dep) && inst->dst.file != BAD_FILE &&
+          !inst->dst.is_null()) {
+         for (unsigned j = 0; j < regs_written(inst); j++)
+            sb.set(byte_offset(inst->dst, REG_SIZE * j), wr_dep);
+      }
+   }
+
+   /**
+    * Calculate scoreboard objects locally that represent any pending (and
+    * unconditionally resolved) dependencies at the end of each block of the
+    * program.
+    */
+   std::vector<scoreboard>
+   gather_block_scoreboards(const fs_visitor *shader,
+                            const std::vector<ordered_address> &jps)
+   {
+      std::vector<scoreboard> sbs(shader->cfg->num_blocks);
+      unsigned ip = 0;
+
+      foreach_block_and_inst(block, fs_inst, inst, shader->cfg)
+         update_inst_scoreboard(shader, jps, inst, ip++, sbs[block->num]);
+
+      return sbs;
+   }
+
+   /**
+    * Propagate data dependencies globally through the control flow graph
+    * until a fixed point is reached.
+    *
+    * Calculates the set of dependencies potentially pending at the beginning
+    * of each block, and returns it as an array of scoreboard objects.
+    */
+   std::pair<std::vector<scoreboard>, std::vector<unsigned>>
+   propagate_block_scoreboards(const fs_visitor *shader,
+                               const std::vector<ordered_address> &jps)
+   {
+      const std::vector<scoreboard> delta_sbs =
+         gather_block_scoreboards(shader, jps);
+      std::vector<scoreboard> in_sbs(shader->cfg->num_blocks);
+      std::vector<scoreboard> out_sbs(shader->cfg->num_blocks);
+      equivalence_relation eq;
+
+      for (bool progress = true; progress;) {
+         progress = false;
+
+         foreach_block(block, shader->cfg) {
+            const scoreboard sb = shadow(in_sbs[block->num],
+                                         delta_sbs[block->num]);
+
+            if (sb != out_sbs[block->num]) {
+               foreach_list_typed(bblock_link, child_link, link,
+                                  &block->children) {
+                  scoreboard &in_sb = in_sbs[child_link->block->num];
+                  const int delta =
+                     jps[child_link->block->start_ip] - jps[block->end_ip]
+                     - ordered_unit(static_cast<const fs_inst *>(block->end()));
+
+                  in_sb = merge(eq, in_sb, transport(sb, delta));
+               }
+
+               out_sbs[block->num] = sb;
+               progress = true;
+            }
+         }
+      }
+
+      return { std::move(in_sbs), eq.flatten() };
+   }
+
+   /**
+    * Return the list of potential dependencies of each instruction in the
+    * shader based on the result of global dependency analysis.
+    */
+   std::vector<std::vector<dependency>>
+   gather_inst_dependencies(const fs_visitor *shader,
+                            const std::vector<ordered_address> &jps)
+   {
+      std::vector<scoreboard> sbs;
+      std::vector<unsigned> ids;
+      std::vector<std::vector<dependency>> deps;
+      unsigned ip = 0;
+
+      std::tie(sbs, ids) = propagate_block_scoreboards(shader, jps);
+
+      foreach_block_and_inst(block, fs_inst, inst, shader->cfg) {
+         scoreboard &sb = sbs[block->num];
+         std::vector<dependency> inst_deps;
+
+         for (unsigned i = 0; i < inst->sources; i++) {
+            for (unsigned j = 0; j < regs_read(inst, i); j++)
+               add_dependency(ids, inst_deps, dependency_for_read(
+                  sb.get(byte_offset(inst->src[i], REG_SIZE * j))));
+         }
+
+         if (is_send(inst) && inst->base_mrf != -1) {
+            for (unsigned j = 0; j < inst->mlen; j++)
+               add_dependency(ids, inst_deps, dependency_for_read(
+                  sb.get(brw_uvec_mrf(8, inst->base_mrf + j, 0))));
+         }
+
+         if (is_unordered(inst))
+            add_dependency(ids, inst_deps, dependency(TGL_SBID_SET, ip));
+
+         if (!inst->no_dd_check) {
+            if (inst->dst.file != BAD_FILE && !inst->dst.is_null()) {
+               for (unsigned j = 0; j < regs_written(inst); j++) {
+                  add_dependency(ids, inst_deps, dependency_for_write(inst,
+                     sb.get(byte_offset(inst->dst, REG_SIZE * j))));
+               }
+            }
+
+            if (is_send(inst) && inst->base_mrf != -1) {
+               for (int j = 0; j < shader->implied_mrf_writes(inst); j++)
+                  add_dependency(ids, inst_deps, dependency_for_write(inst,
+                     sb.get(brw_uvec_mrf(8, inst->base_mrf + j, 0))));
+            }
+         }
+
+         deps.push_back(inst_deps);
+         update_inst_scoreboard(shader, jps, inst, ip, sb);
+         ip++;
+      }
+
+      return deps;
+   }
+
+   /** @} */
+
+   /**
+    * Allocate SBID tokens to track the execution of every out-of-order
+    * instruction of the shader.
+    */
+   std::vector<std::vector<dependency>>
+   allocate_inst_dependencies(const fs_visitor *shader,
+                              const std::vector<std::vector<dependency>> &deps0)
+   {
+      /* XXX - Use bin-packing algorithm to assign hardware SBIDs optimally in
+       *       shaders with a large number of SEND messages.
+       */
+      std::vector<std::vector<dependency>> deps1;
+      std::vector<unsigned> ids(deps0.size(), ~0u);
+      unsigned next_id = 0;
+
+      for (const auto &inst_deps0 : deps0) {
+         std::vector<dependency> inst_deps1;
+
+         for (const auto &dep : inst_deps0) {
+            if (dep.unordered && ids[dep.id] == ~0u)
+               ids[dep.id] = (next_id++) & 0xf;
+
+            add_dependency(ids, inst_deps1, dep);
+         }
+
+         deps1.push_back(inst_deps1);
+      }
+
+      return deps1;
+   }
+
+   /**
+    * Emit dependency information provided by \p deps into the shader,
+    * inserting additional SYNC instructions for dependencies that can't be
+    * represented directly by annotating existing instructions.
+    */
+   void
+   emit_inst_dependencies(fs_visitor *shader,
+                          const std::vector<ordered_address> &jps,
+                          const std::vector<std::vector<dependency>> &deps)
+   {
+      unsigned ip = 0;
+
+      foreach_block_and_inst_safe(block, fs_inst, inst, shader->cfg) {
+         tgl_swsb swsb = ordered_dependency_swsb(deps[ip], jps[ip]);
+         const tgl_sbid_mode unordered_mode =
+            baked_unordered_dependency_mode(inst, deps[ip], jps[ip]);
+
+         for (const auto &dep : deps[ip]) {
+            if (dep.unordered) {
+               if (unordered_mode == dep.unordered && !swsb.mode) {
+                  /* Bake unordered dependency into the instruction's SWSB if
+                   * possible.
+                   */
+                  swsb.sbid = dep.id;
+                  swsb.mode = dep.unordered;
+               } else {
+                  /* Emit dependency into the SWSB of an extra SYNC
+                   * instruction.
+                   */
+                  const fs_builder ibld = fs_builder(shader, block, inst)
+                     .exec_all().group(1, 0);
+                  fs_inst *sync = ibld.emit(BRW_OPCODE_SYNC, ibld.null_reg_ud(),
+                                            brw_imm_ud(TGL_SYNC_NOP));
+                  sync->sched.sbid = dep.id;
+                  sync->sched.mode = dep.unordered;
+                  assert(!(sync->sched.mode & TGL_SBID_SET));
+               }
+            }
+         }
+
+         /* Update the IR. */
+         inst->sched = swsb;
+         inst->no_dd_check = inst->no_dd_clear = false;
+         ip++;
+      }
+   }
+}
+
+bool
+fs_visitor::lower_scoreboard()
+{
+   if (devinfo->gen >= 12) {
+      const std::vector<ordered_address> jps = ordered_inst_addresses(this);
+      emit_inst_dependencies(this, jps,
+         allocate_inst_dependencies(this,
+            gather_inst_dependencies(this, jps)));
+   }
+
+   return true;
+}
diff --git a/src/intel/compiler/meson.build b/src/intel/compiler/meson.build
index d74caa0632b..0a782fa70f1 100644
--- a/src/intel/compiler/meson.build
+++ b/src/intel/compiler/meson.build
@@ -62,6 +62,7 @@ libintel_compiler_files = files(
   'brw_fs_reg_allocate.cpp',
   'brw_fs_register_coalesce.cpp',
   'brw_fs_saturate_propagation.cpp',
+  'brw_fs_scoreboard.cpp',
   'brw_fs_sel_peephole.cpp',
   'brw_fs_validate.cpp',
   'brw_fs_visitor.cpp',