[ir] deleted mask/merge instructions; will be replaced by masked_load/store and select

lib/codegen/optimize_dce.cpp

@@ -0,0 +1,60 @@
+#include "triton/ir/function.h"
+#include "triton/ir/basic_block.h"
+#include "triton/ir/module.h"
+#include "triton/ir/cfg.h"
+#include "triton/codegen/optimize_dce.h"
+
+namespace triton {
+namespace codegen{
+
+
+void optimize_dce::run(ir::module &mod) {
+  std::list<ir::instruction*> work_list;
+  std::set<ir::instruction*> marked;
+
+  // initialize work-list
+  for(ir::function *fn: mod.get_function_list()){
+    std::vector<ir::basic_block*> rpo = ir::cfg::reverse_post_order(fn);
+    // iterate through blocks
+    for(ir::basic_block *block: rpo)
+    for(ir::instruction *i: block->get_inst_list()){
+      if(dynamic_cast<ir::io_inst*>(i) || dynamic_cast<ir::copy_to_shared_inst*>(i) || dynamic_cast<ir::return_inst*>(i)
+         || dynamic_cast<ir::branch_inst*>(i) || dynamic_cast<ir::cond_branch_inst*>(i)){
+        work_list.push_back(i);
+        marked.insert(i);
+      }
+    }
+  }
+
+  // mark -- ignore branches
+  while(!work_list.empty()){
+    ir::instruction* current = work_list.back();
+    work_list.pop_back();
+    // mark instruction operands
+    for(ir::value* op: current->ops()) {
+      if(auto *i = dynamic_cast<ir::instruction*>(op))
+        if(marked.insert(i).second)
+          work_list.push_back(i);
+    }
+    // TODO: mark last intstruction of current's reverse-dominance frontier
+  }
+
+  // sweep -- delete non-branch unmarked instructions
+  std::vector<ir::instruction*> to_delete;
+  for(ir::function *fn: mod.get_function_list()){
+    std::vector<ir::basic_block*> rpo = ir::cfg::reverse_post_order(fn);
+    // iterate through blocks
+    for(ir::basic_block *block: rpo)
+    for(ir::instruction *i: block->get_inst_list()){
+      if(marked.find(i) == marked.end())
+        to_delete.push_back(i);
+    }
+  }
+
+  // delete
+  for(ir::instruction* i: to_delete)
+    i->erase_from_parent();
+}
+
+}
+}