Basic ContextPromotionPass and some opcode info rearranging.

src/alloy/compiler/passes/context_promotion_pass.cc

@@ -0,0 +1,109 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2013 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include <alloy/compiler/passes/context_promotion_pass.h>
+
+#include <alloy/compiler/compiler.h>
+#include <alloy/runtime/runtime.h>
+
+using namespace alloy;
+using namespace alloy::compiler;
+using namespace alloy::compiler::passes;
+using namespace alloy::frontend;
+using namespace alloy::hir;
+using namespace alloy::runtime;
+
+
+ContextPromotionPass::ContextPromotionPass() :
+    context_values_size_(0), context_values_(0),
+    Pass() {
+}
+
+ContextPromotionPass::~ContextPromotionPass() {
+  if (context_values_) {
+    xe_free(context_values_);
+  }
+}
+
+int ContextPromotionPass::Initialize(Compiler* compiler) {
+  if (Pass::Initialize(compiler)) {
+    return 1;
+  }
+
+  // This is a terrible implementation.
+  ContextInfo* context_info = runtime_->frontend()->context_info();
+  context_values_size_ = context_info->size() * sizeof(Value*);
+  context_values_ = (Value**)xe_calloc(context_values_size_);
+
+  return 0;
+}
+
+int ContextPromotionPass::Run(FunctionBuilder* builder) {
+  // Like mem2reg, but because context memory is unaliasable it's easier to
+  // check and convert LoadContext/StoreContext into value operations.
+  // Example of load->value promotion:
+  //   v0 = load_context +100
+  //   store_context +200, v0
+  //   v1 = load_context +100  <-- replace with v1 = v0
+  //   store_context +200, v1
+  //
+  // It'd be possible in this stage to also remove redundant context stores:
+  // Example of dead store elimination:
+  //   store_context +100, v0  <-- removed due to following store
+  //   store_context +100, v1
+  // This is more generally done by DSE, however if it could be done here
+  // instead as it may be faster (at least on the block-level).
+
+  // Process each block independently, for now.
+  Block* block = builder->first_block();
+  while (block) {
+    PromoteBlock(block);
+    block = block->next;
+  }
+
+  return 0;
+}
+
+void ContextPromotionPass::PromoteBlock(Block* block) {
+  // Clear the context values list.
+  // TODO(benvanik): new data structure that isn't so stupid.
+  //     Bitvector of validity, perhaps?
+  xe_zero_struct(context_values_, context_values_size_);
+
+  Instr* i = block->instr_head;
+  while (i) {
+    if (i->opcode == &OPCODE_LOAD_CONTEXT_info) {
+      size_t offset = i->src1.offset;
+      Value* previous_value = context_values_[offset];
+      if (previous_value) {
+        // Legit previous value, reuse.
+        i->opcode = &hir::OPCODE_ASSIGN_info;
+        i->set_src1(previous_value);
+      } else {
+        // Store the loaded value into the table.
+        context_values_[offset] = i->dest;
+      }
+    } else if (i->opcode == &OPCODE_STORE_CONTEXT_info) {
+      size_t offset = i->src1.offset;
+      Value* value = i->src2.value;
+      Value* previous_value = context_values_[offset];
+      if (previous_value &&
+          previous_value->def &&
+          previous_value->def->opcode == &OPCODE_STORE_CONTEXT_info) {
+        // Legit previous value from a useless store.
+        // Remove the store entirely.
+        previous_value->def->Remove();
+      }
+      // Store value into the table for later.
+      context_values_[offset] = value;
+    }
+
+    i = i->next;
+  }
+}