Adding control flow simplification pass to compensate for lack of phi.

src/alloy/compiler/passes/control_flow_simplification_pass.cc

@@ -0,0 +1,60 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2014 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include <alloy/compiler/passes/control_flow_simplification_pass.h>
+
+#include <alloy/backend/backend.h>
+#include <alloy/compiler/compiler.h>
+#include <alloy/runtime/runtime.h>
+
+namespace alloy {
+namespace compiler {
+namespace passes {
+
+// TODO(benvanik): remove when enums redefined.
+using namespace alloy::hir;
+
+using alloy::hir::Edge;
+using alloy::hir::HIRBuilder;
+
+ControlFlowSimplificationPass::ControlFlowSimplificationPass()
+    : CompilerPass() {}
+
+ControlFlowSimplificationPass::~ControlFlowSimplificationPass() {}
+
+int ControlFlowSimplificationPass::Run(HIRBuilder* builder) {
+  SCOPE_profile_cpu_f("alloy");
+
+  // Walk backwards and merge blocks if possible.
+  bool merged_any = false;
+  auto block = builder->last_block();
+  while (block) {
+    auto prev_block = block->prev;
+    const uint32_t expected = Edge::DOMINATES | Edge::UNCONDITIONAL;
+    if (block->incoming_edge_head &&
+        (block->incoming_edge_head->flags & expected) == expected) {
+      // Dominated by the incoming block.
+      // If that block comes immediately before us then we can merge the
+      // two blocks (assuming it's not a volatile instruction like Trap).
+      if (block->prev == block->incoming_edge_head->src &&
+          block->prev->instr_tail &&
+          !(block->prev->instr_tail->opcode->flags & OPCODE_FLAG_VOLATILE)) {
+        builder->MergeAdjacentBlocks(block->prev, block);
+        merged_any = true;
+      }
+    }
+    block = prev_block;
+  }
+
+  return 0;
+}
+
+}  // namespace passes
+}  // namespace compiler
+}  // namespace alloy