[AArch64] Enable SeparateConstOffsetFromGEP, EarlyCSE and LICM passes on AArch64 backend.

SeparateConstOffsetFromGEP can gives more optimizaiton opportunities related to GEPs, which benefits EarlyCSE
and LICM. By enabling these passes we can have better address calculations and generate a better addressing
mode. Some SPEC 2006 benchmarks (astar, gobmk, namd) have obvious improvements on Cortex-A57.

Reviewed in http://reviews.llvm.org/D5864.

llvm-svn: 222331

1 files changed, 18 insertions, 0 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp b/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
index fa17c064194..79b1a7fddba 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
@@ -81,6 +81,11 @@ EnableA53Fix835769("aarch64-fix-cortex-a53-835769", cl::Hidden,
                 cl::desc("Work around Cortex-A53 erratum 835769"),
                 cl::init(false));
 
+static cl::opt<bool>
+EnableGEPOpt("aarch64-gep-opt", cl::Hidden,
+             cl::desc("Enable optimizations on complex GEPs"),
+             cl::init(true));
+
 extern "C" void LLVMInitializeAArch64Target() {
   // Register the target.
   RegisterTargetMachine<AArch64leTargetMachine> X(TheAArch64leTarget);
@@ -205,6 +210,19 @@ void AArch64PassConfig::addIRPasses() {
     addPass(createCFGSimplificationPass());
 
   TargetPassConfig::addIRPasses();
+
+  if (TM->getOptLevel() == CodeGenOpt::Aggressive && EnableGEPOpt) {
+    // Call SeparateConstOffsetFromGEP pass to extract constants within indices
+    // and lower a GEP with multiple indices to either arithmetic operations or
+    // multiple GEPs with single index.
+    addPass(createSeparateConstOffsetFromGEPPass(TM, true));
+    // Call EarlyCSE pass to find and remove subexpressions in the lowered
+    // result.
+    addPass(createEarlyCSEPass());
+    // Do loop invariant code motion in case part of the lowered result is
+    // invariant.
+    addPass(createLICMPass());
+  }
 }
 
 // Pass Pipeline Configuration