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

src/alloy/compiler/compiler_passes.h

@@ -11,8 +11,9 @@
 #define ALLOY_COMPILER_COMPILER_PASSES_H_
 
 #include <alloy/compiler/passes/constant_propagation_pass.h>
-#include <alloy/compiler/passes/control_flow_analysis_pass.h>
 #include <alloy/compiler/passes/context_promotion_pass.h>
+#include <alloy/compiler/passes/control_flow_analysis_pass.h>
+#include <alloy/compiler/passes/control_flow_simplification_pass.h>
 #include <alloy/compiler/passes/data_flow_analysis_pass.h>
 #include <alloy/compiler/passes/dead_code_elimination_pass.h>
 //#include <alloy/compiler/passes/dead_store_elimination_pass.h>

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

src/alloy/compiler/passes/control_flow_simplification_pass.h

@@ -0,0 +1,33 @@
+/**
+ ******************************************************************************
+ * 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. *
+ ******************************************************************************
+ */
+
+#ifndef ALLOY_COMPILER_PASSES_CONTROL_FLOW_SIMPLIFICATION_PASS_H_
+#define ALLOY_COMPILER_PASSES_CONTROL_FLOW_SIMPLIFICATION_PASS_H_
+
+#include <alloy/compiler/compiler_pass.h>
+
+namespace alloy {
+namespace compiler {
+namespace passes {
+
+class ControlFlowSimplificationPass : public CompilerPass {
+ public:
+  ControlFlowSimplificationPass();
+  ~ControlFlowSimplificationPass() override;
+
+  int Run(hir::HIRBuilder* builder) override;
+
+ private:
+};
+
+}  // namespace passes
+}  // namespace compiler
+}  // namespace alloy
+
+#endif  // ALLOY_COMPILER_PASSES_CONTROL_FLOW_SIMPLIFICATION_PASS_H_

src/alloy/compiler/passes/register_allocation_pass.cc

@@ -320,8 +320,7 @@ bool RegisterAllocationPass::TryAllocateRegister(Value* value) {
   return false;
 }
 
-bool RegisterAllocationPass::SpillOneRegister(HIRBuilder* builder,
-                                              Block* block,
+bool RegisterAllocationPass::SpillOneRegister(HIRBuilder* builder, Block* block,
                                               TypeName required_type) {
   // Get the set that we will be picking from.
   RegisterSetUsage* usage_set;

src/alloy/compiler/passes/sources.gypi

@@ -7,6 +7,8 @@
     'context_promotion_pass.h',
     'control_flow_analysis_pass.cc',
     'control_flow_analysis_pass.h',
+    'control_flow_simplification_pass.cc',
+    'control_flow_simplification_pass.h',
     'data_flow_analysis_pass.cc',
     'data_flow_analysis_pass.h',
     'dead_code_elimination_pass.cc',