Add an experimental option to run gep-splitting and no-load GVN

just before codegen.

llvm-svn: 89439

1 files changed, 11 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/LLVMTargetMachine.cpp b/llvm/lib/CodeGen/LLVMTargetMachine.cpp
index 0db459bb916..8800f22beb5 100644
--- a/llvm/lib/CodeGen/LLVMTargetMachine.cpp
+++ b/llvm/lib/CodeGen/LLVMTargetMachine.cpp
@@ -66,6 +66,11 @@ static cl::opt<cl::boolOrDefault>
 EnableFastISelOption("fast-isel", cl::Hidden,
   cl::desc("Enable the \"fast\" instruction selector"));
 
+// Enable or disable an experimental optimization to split GEPs
+// and run a special GVN pass which does not examine loads, in
+// an effort to factor out redundancy implicit in complex GEPs.
+static cl::opt<bool> EnableSplitGEPGVN("split-gep-gvn", cl::Hidden,
+    cl::desc("Split GEPs and run no-load GVN"));
 
 LLVMTargetMachine::LLVMTargetMachine(const Target &T,
                                      const std::string &TargetTriple)
@@ -223,6 +228,12 @@ bool LLVMTargetMachine::addCommonCodeGenPasses(PassManagerBase &PM,
                                                CodeGenOpt::Level OptLevel) {
   // Standard LLVM-Level Passes.
 
+  // Optionally, tun split-GEPs and no-load GVN.
+  if (EnableSplitGEPGVN) {
+    PM.add(createGEPSplitterPass());
+    PM.add(createGVNPass(/*NoPRE=*/false, /*NoLoads=*/true));
+  }
+
   // Run loop strength reduction before anything else.
   if (OptLevel != CodeGenOpt::None && !DisableLSR) {
     PM.add(createLoopStrengthReducePass(getTargetLowering()));