Eliminate unused allocas.
Bug swiftshader:27
Change-Id: If085323dc6cc4325c6ff55c1021e98db94a75302
Reviewed-on: https://swiftshader-review.googlesource.com/8228
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
diff --git a/src/Reactor/Optimizer.cpp b/src/Reactor/Optimizer.cpp
new file mode 100644
index 0000000..b528993
--- /dev/null
+++ b/src/Reactor/Optimizer.cpp
@@ -0,0 +1,110 @@
+// Copyright 2016 The SwiftShader Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "Optimizer.hpp"
+
+#include "src/IceCfg.h"
+#include "src/IceCfgNode.h"
+
+#include <map>
+#include <vector>
+
+namespace
+{
+ class Optimizer
+ {
+ public:
+ void run(Ice::Cfg *function);
+
+ private:
+ void analyzeUses(Ice::Cfg *function);
+ void eliminateUnusedAllocas();
+
+ Ice::Cfg *function;
+
+ std::map<Ice::Operand*, std::vector<Ice::Inst*>> uses;
+ };
+
+ void Optimizer::run(Ice::Cfg *function)
+ {
+ this->function = function;
+
+ analyzeUses(function);
+
+ eliminateUnusedAllocas();
+ }
+
+ void Optimizer::eliminateUnusedAllocas()
+ {
+ Ice::CfgNode *entryBlock = function->getEntryNode();
+
+ for(Ice::Inst &alloca : entryBlock->getInsts())
+ {
+ if(!llvm::isa<Ice::InstAlloca>(alloca))
+ {
+ return; // Allocas are all at the top
+ }
+
+ Ice::Operand *address = alloca.getDest();
+
+ if(uses[address].empty())
+ {
+ alloca.setDeleted();
+ }
+ }
+ }
+
+ void Optimizer::analyzeUses(Ice::Cfg *function)
+ {
+ uses.clear();
+
+ for(Ice::CfgNode *basicBlock : function->getNodes())
+ {
+ for(Ice::Inst &instruction : basicBlock->getInsts())
+ {
+ if(instruction.isDeleted())
+ {
+ continue;
+ }
+
+ for(int i = 0; i < instruction.getSrcSize(); i++)
+ {
+ int unique = 0;
+ for(; unique < i; unique++)
+ {
+ if(instruction.getSrc(i) == instruction.getSrc(unique))
+ {
+ break;
+ }
+ }
+
+ if(i == unique)
+ {
+ uses[instruction.getSrc(i)].push_back(&instruction);
+ }
+ }
+ }
+ }
+ }
+}
+
+namespace sw
+{
+ void optimize(Ice::Cfg *function)
+ {
+ Optimizer optimizer;
+
+ optimizer.run(function);
+ }
+}
\ No newline at end of file
