[mips] Implement the following optimizations using dominance information to

make PIC calls a little more efficient:

1. Remove instructions setting up $gp if it is known that a function has been
   called at least once.
2. Save the address of a called function in a register instead of loading
   it from the GOT at every call site.

llvm-svn: 195892

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Target/Mips/MipsTargetMachine.cpp b/llvm/lib/Target/Mips/MipsTargetMachine.cpp
index 5046c1b..ab5677a 100644
--- a/llvm/lib/Target/Mips/MipsTargetMachine.cpp
+++ b/llvm/lib/Target/Mips/MipsTargetMachine.cpp
@@ -153,6 +153,7 @@ public:
 
   virtual void addIRPasses();
   virtual bool addInstSelector();
+  virtual void addMachineSSAOptimization();
   virtual bool addPreEmitPass();
 };
 } // namespace
@@ -182,6 +183,11 @@ bool MipsPassConfig::addInstSelector() {
   return false;
 }
 
+void MipsPassConfig::addMachineSSAOptimization() {
+  addPass(createMipsOptimizePICCallPass(getMipsTargetMachine()));
+  TargetPassConfig::addMachineSSAOptimization();
+}
+
 void MipsTargetMachine::addAnalysisPasses(PassManagerBase &PM) {
   if (Subtarget.allowMixed16_32()) {
     DEBUG(errs() << "No ");