Peephole optimization pass on final machine code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3840 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/PostOpts/Makefile

@@ -0,0 +1,9 @@
+LEVEL = ../../..
+
+DIRS  = 
+
+LIBRARYNAME = postopts
+
+BUILD_ARCHIVE = 1
+
+include $(LEVEL)/Makefile.common

lib/Target/SparcV9/SparcV9PeepholeOpts.cpp

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+// $Id$ -*-c++-*-
+//***************************************************************************
+// File:
+//	PeepholeOpts.h
+// 
+// Purpose:
+//	Support for performing several peephole opts in one or a few passes
+//      over the machine code of a method.
+//**************************************************************************/
+
+
+#include "llvm/CodeGen/PeepholeOpts.h"
+#include "llvm/CodeGen/MachineCodeForBasicBlock.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/MachineInstrInfo.h"
+#include "llvm/Target/MachineOptInfo.h"
+#include "llvm/BasicBlock.h"
+#include "llvm/Pass.h"
+
+
+//********************* Internal Class Declarations ************************/
+
+
+//************************* Internal Functions *****************************/
+
+inline void
+DeleteInstruction(MachineCodeForBasicBlock& mvec,
+                  MachineCodeForBasicBlock::iterator& BBI,
+                  const TargetMachine& target)
+{
+  // Check if this instruction is in a delay slot of its predecessor.
+  // If so, replace this instruction with a nop, else just delete it.
+  // By replacing in place, we save having to update the I-I maps.
+  if (BBI != mvec.begin())
+    {
+      const MachineInstrInfo& mii = target.getInstrInfo();
+      MachineInstr* predMI = *(BBI-1);
+      if (unsigned ndelay = mii.getNumDelaySlots(predMI->getOpCode()))
+        {
+          assert(ndelay == 1 && "Not yet handling multiple-delay-slot targets");
+          (*BBI)->replace(mii.getNOPOpCode(), 0);
+        }
+    }
+  else
+    {
+      mvec.erase(BBI);
+      BBI = mvec.end();
+    }
+}
+
+//******************* Individual Peephole Optimizations ********************/
+
+
+inline bool
+RemoveUselessCopies(MachineCodeForBasicBlock& mvec,
+                    MachineCodeForBasicBlock::iterator& BBI,
+                    const TargetMachine& target)
+{
+  if (target.getOptInfo().IsUselessCopy(*BBI))
+    {
+      DeleteInstruction(mvec, BBI, target);
+      return true;
+    }
+  return false;
+}
+
+
+//************************ Class Implementations **************************/
+
+class PeepholeOpts: public BasicBlockPass {
+  const TargetMachine ⌖
+  bool visit(MachineCodeForBasicBlock& mvec,
+             MachineCodeForBasicBlock::iterator BBI) const;
+public:
+  PeepholeOpts(const TargetMachine &T): target(T) { }
+  bool runOnBasicBlock(BasicBlock &BB); // apply this pass to each BB
+};
+
+
+// Register the pass with llc only, and not opt...
+static RegisterLLC<PeepholeOpts>
+X("peephole", "Peephole Optimization", createPeepholeOptsPass);
+
+
+/* Apply a list of peephole optimizations to this machine instruction
+ * within its local context.  They are allowed to delete MI or any
+ * instruction before MI, but not 
+ */
+bool
+PeepholeOpts::visit(MachineCodeForBasicBlock& mvec,
+                    MachineCodeForBasicBlock::iterator BBI) const
+{
+  bool changed = false;
+
+  /* Remove redundant copy instructions */
+  changed |= RemoveUselessCopies(mvec, BBI, target);
+  if (BBI == mvec.end())                // nothing more to do!
+    return changed;
+
+  return changed;
+}
+
+
+bool
+PeepholeOpts::runOnBasicBlock(BasicBlock &BB)
+{
+  // Get the machine instructions for this BB
+  MachineCodeForBasicBlock& mvec = MachineCodeForBasicBlock::get(&BB);
+
+  // Iterate over all machine instructions in the BB
+  // Use a reverse iterator to allow deletion of MI or any instruction after it.
+  // Insertions or deletions *before* MI are not safe.
+  // 
+  for (MachineCodeForBasicBlock::reverse_iterator RI=mvec.rbegin(),
+         RE=mvec.rend(); RI != RE; )
+    {
+      MachineCodeForBasicBlock::iterator BBI = RI.base()-1; // save before incr
+      ++RI;             // pre-increment to delete MI or after it
+      visit(mvec, BBI);
+    }
+
+  return true;
+}
+
+
+//===----------------------------------------------------------------------===//
+// createPeepholeOptsPass - Public entrypoint for peephole optimization
+// and this file as a whole...
+//
+Pass*
+createPeepholeOptsPass(TargetMachine &T)
+{
+  return new PeepholeOpts(T);
+}
+