aco: Initial commit of independent AMD compiler

ACO (short for AMD Compiler) is a new compiler backend with the goal to replace
LLVM for Radeon hardware for the RADV driver.

ACO currently supports only VS, PS and CS on VI and Vega.
There are some optimizations missing because of unmerged NIR changes
which may decrease performance.

Full commit history can be found at
https://github.com/daniel-schuermann/mesa/commits/backend

Co-authored-by: Daniel Schürmann <daniel@schuermann.dev>
Co-authored-by: Rhys Perry <pendingchaos02@gmail.com>
Co-authored-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Co-authored-by: Connor Abbott <cwabbott0@gmail.com>
Co-authored-by: Michael Schellenberger Costa <mschellenbergercosta@googlemail.com>
Co-authored-by: Timur Kristóf <timur.kristof@gmail.com>

Acked-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Acked-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>

1 files changed, 291 insertions, 0 deletions

diff --git a/src/amd/compiler/aco_ssa_elimination.cpp b/src/amd/compiler/aco_ssa_elimination.cpp
new file mode 100644
index 00000000000..3d76dcd8867
--- /dev/null
+++ b/src/amd/compiler/aco_ssa_elimination.cpp
@@ -0,0 +1,291 @@
+/*
+ * Copyright © 2018 Valve 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.
+ *
+ */
+
+
+#include "aco_ir.h"
+
+#include <map>
+
+namespace aco {
+namespace {
+
+/* map: block-id -> pair (dest, src) to store phi information */
+typedef std::map<uint32_t, std::vector<std::pair<Definition, Operand>>> phi_info;
+
+struct ssa_elimination_ctx {
+   phi_info logical_phi_info;
+   phi_info linear_phi_info;
+   std::vector<bool> empty_blocks;
+   Program* program;
+
+   ssa_elimination_ctx(Program* program) : empty_blocks(program->blocks.size(), true), program(program) {}
+};
+
+void collect_phi_info(ssa_elimination_ctx& ctx)
+{
+   for (Block& block : ctx.program->blocks) {
+      for (aco_ptr<Instruction>& phi : block.instructions) {
+         if (phi->opcode != aco_opcode::p_phi && phi->opcode != aco_opcode::p_linear_phi)
+            break;
+
+         for (unsigned i = 0; i < phi->operands.size(); i++) {
+            if (phi->operands[i].isUndefined())
+               continue;
+            if (phi->operands[i].isTemp() && phi->operands[i].physReg() == phi->definitions[0].physReg())
+               continue;
+
+            std::vector<unsigned>& preds = phi->opcode == aco_opcode::p_phi ? block.logical_preds : block.linear_preds;
+            phi_info& info = phi->opcode == aco_opcode::p_phi ? ctx.logical_phi_info : ctx.linear_phi_info;
+            const auto result = info.emplace(preds[i], std::vector<std::pair<Definition, Operand>>());
+            result.first->second.emplace_back(phi->definitions[0], phi->operands[i]);
+            ctx.empty_blocks[preds[i]] = false;
+         }
+      }
+   }
+}
+
+void insert_parallelcopies(ssa_elimination_ctx& ctx)
+{
+   /* insert the parallelcopies from logical phis before p_logical_end */
+   for (auto&& entry : ctx.logical_phi_info) {
+      Block& block = ctx.program->blocks[entry.first];
+      unsigned idx = block.instructions.size() - 1;
+      while (block.instructions[idx]->opcode != aco_opcode::p_logical_end) {
+         assert(idx > 0);
+         idx--;
+      }
+
+      std::vector<aco_ptr<Instruction>>::iterator it = std::next(block.instructions.begin(), idx);
+      aco_ptr<Pseudo_instruction> pc{create_instruction<Pseudo_instruction>(aco_opcode::p_parallelcopy, Format::PSEUDO, entry.second.size(), entry.second.size())};
+      unsigned i = 0;
+      for (std::pair<Definition, Operand>& pair : entry.second)
+      {
+         pc->definitions[i] = pair.first;
+         pc->operands[i] = pair.second;
+         i++;
+      }
+      /* this shouldn't be needed since we're only copying vgprs */
+      pc->tmp_in_scc = false;
+      block.instructions.insert(it, std::move(pc));
+   }
+
+   /* insert parallelcopies for the linear phis at the end of blocks just before the branch */
+   for (auto&& entry : ctx.linear_phi_info) {
+      Block& block = ctx.program->blocks[entry.first];
+      std::vector<aco_ptr<Instruction>>::iterator it = block.instructions.end();
+      --it;
+      assert((*it)->format == Format::PSEUDO_BRANCH);
+      aco_ptr<Pseudo_instruction> pc{create_instruction<Pseudo_instruction>(aco_opcode::p_parallelcopy, Format::PSEUDO, entry.second.size(), entry.second.size())};
+      unsigned i = 0;
+      for (std::pair<Definition, Operand>& pair : entry.second)
+      {
+         pc->definitions[i] = pair.first;
+         pc->operands[i] = pair.second;
+         i++;
+      }
+      pc->tmp_in_scc = block.scc_live_out;
+      pc->scratch_sgpr = block.scratch_sgpr;
+      block.instructions.insert(it, std::move(pc));
+   }
+}
+
+
+void try_remove_merge_block(ssa_elimination_ctx& ctx, Block* block)
+{
+   /* check if the successor is another merge block which restores exec */
+   // TODO: divergent loops also restore exec
+   if (block->linear_succs.size() != 1 ||
+       !(ctx.program->blocks[block->linear_succs[0]].kind & block_kind_merge))
+      return;
+
+   /* check if this block is empty and the exec mask is not needed */
+   for (aco_ptr<Instruction>& instr : block->instructions) {
+      if (instr->opcode == aco_opcode::p_parallelcopy) {
+         if (instr->definitions[0].physReg() == exec)
+            continue;
+         else
+            return;
+      }
+
+      if (instr->opcode != aco_opcode::p_linear_phi &&
+          instr->opcode != aco_opcode::p_phi &&
+          instr->opcode != aco_opcode::p_logical_start &&
+          instr->opcode != aco_opcode::p_logical_end &&
+          instr->opcode != aco_opcode::p_branch)
+         return;
+   }
+
+   /* keep the branch instruction and remove the rest */
+   aco_ptr<Instruction> branch = std::move(block->instructions.back());
+   block->instructions.clear();
+   block->instructions.emplace_back(std::move(branch));
+}
+
+void try_remove_invert_block(ssa_elimination_ctx& ctx, Block* block)
+{
+   assert(block->linear_succs.size() == 2);
+   if (block->linear_succs[0] != block->linear_succs[1])
+      return;
+
+   /* check if we can remove this block */
+   for (aco_ptr<Instruction>& instr : block->instructions) {
+      if (instr->opcode != aco_opcode::p_linear_phi &&
+          instr->opcode != aco_opcode::p_phi &&
+          instr->opcode != aco_opcode::s_andn2_b64 &&
+          instr->opcode != aco_opcode::p_branch)
+         return;
+   }
+
+   unsigned succ_idx = block->linear_succs[0];
+   assert(block->linear_preds.size() == 2);
+   for (unsigned i = 0; i < 2; i++) {
+      Block *pred = &ctx.program->blocks[block->linear_preds[i]];
+      pred->linear_succs[0] = succ_idx;
+      ctx.program->blocks[succ_idx].linear_preds[i] = pred->index;
+
+      Pseudo_branch_instruction *branch = static_cast<Pseudo_branch_instruction*>(pred->instructions.back().get());
+      assert(branch->format == Format::PSEUDO_BRANCH);
+      branch->target[0] = succ_idx;
+      branch->target[1] = succ_idx;
+   }
+
+   block->instructions.clear();
+   block->linear_preds.clear();
+   block->linear_succs.clear();
+}
+
+void try_remove_simple_block(ssa_elimination_ctx& ctx, Block* block)
+{
+   for (aco_ptr<Instruction>& instr : block->instructions) {
+      if (instr->opcode != aco_opcode::p_logical_start &&
+          instr->opcode != aco_opcode::p_logical_end &&
+          instr->opcode != aco_opcode::p_branch)
+         return;
+   }
+
+   Block& pred = ctx.program->blocks[block->linear_preds[0]];
+   Block& succ = ctx.program->blocks[block->linear_succs[0]];
+   Pseudo_branch_instruction* branch = static_cast<Pseudo_branch_instruction*>(pred.instructions.back().get());
+   if (branch->opcode == aco_opcode::p_branch) {
+      branch->target[0] = succ.index;
+      branch->target[1] = succ.index;
+   } else if (branch->target[0] == block->index) {
+      branch->target[0] = succ.index;
+   } else if (branch->target[0] == succ.index) {
+      assert(branch->target[1] == block->index);
+      branch->target[1] = succ.index;
+      branch->opcode = aco_opcode::p_branch;
+   } else if (branch->target[1] == block->index) {
+      /* check if there is a fall-through path from block to succ */
+      bool falls_through = true;
+      for (unsigned j = block->index + 1; falls_through && j < succ.index; j++) {
+         assert(ctx.program->blocks[j].index == j);
+         if (!ctx.program->blocks[j].instructions.empty())
+            falls_through = false;
+      }
+      if (falls_through) {
+         branch->target[1] = succ.index;
+      } else {
+         /* check if there is a fall-through path for the alternative target */
+         for (unsigned j = block->index + 1; j < branch->target[0]; j++) {
+            if (!ctx.program->blocks[j].instructions.empty())
+               return;
+         }
+
+         /* This is a (uniform) break or continue block. The branch condition has to be inverted. */
+         if (branch->opcode == aco_opcode::p_cbranch_z)
+            branch->opcode = aco_opcode::p_cbranch_nz;
+         else if (branch->opcode == aco_opcode::p_cbranch_nz)
+            branch->opcode = aco_opcode::p_cbranch_z;
+         else
+            assert(false);
+         /* also invert the linear successors */
+         pred.linear_succs[0] = pred.linear_succs[1];
+         pred.linear_succs[1] = succ.index;
+         branch->target[1] = branch->target[0];
+         branch->target[0] = succ.index;
+      }
+   } else {
+      assert(false);
+   }
+
+   if (branch->target[0] == branch->target[1])
+      branch->opcode = aco_opcode::p_branch;
+
+   for (unsigned i = 0; i < pred.linear_succs.size(); i++)
+      if (pred.linear_succs[i] == block->index)
+         pred.linear_succs[i] = succ.index;
+
+   for (unsigned i = 0; i < succ.linear_preds.size(); i++)
+      if (succ.linear_preds[i] == block->index)
+         succ.linear_preds[i] = pred.index;
+
+   block->instructions.clear();
+   block->linear_preds.clear();
+   block->linear_succs.clear();
+}
+
+void jump_threading(ssa_elimination_ctx& ctx)
+{
+   for (int i = ctx.program->blocks.size() - 1; i >= 0; i--) {
+      Block* block = &ctx.program->blocks[i];
+
+      if (!ctx.empty_blocks[i])
+         continue;
+
+      if (block->kind & block_kind_invert) {
+         try_remove_invert_block(ctx, block);
+         continue;
+      }
+
+      if (block->linear_succs.size() > 1)
+         continue;
+
+      if (block->kind & block_kind_merge ||
+          block->kind & block_kind_loop_exit)
+         try_remove_merge_block(ctx, block);
+
+      if (block->linear_preds.size() == 1)
+         try_remove_simple_block(ctx, block);
+   }
+}
+
+} /* end namespace */
+
+
+void ssa_elimination(Program* program)
+{
+   ssa_elimination_ctx ctx(program);
+
+   /* Collect information about every phi-instruction */
+   collect_phi_info(ctx);
+
+   /* eliminate empty blocks */
+   jump_threading(ctx);
+
+   /* insert parallelcopies from SSA elimination */
+   insert_parallelcopies(ctx);
+
+}
+}