Add code pulled out of TransformInternals.cpp, ConstProp.cpp, and DCE.cpp
llvm-svn: 2513
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
new file mode 100644
index 0000000..3662264
--- /dev/null
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -0,0 +1,111 @@
+//===-- Local.cpp - Functions to perform local transformations ------------===//
+//
+// This family of functions perform various local transformations to the
+// program.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/iTerminators.h"
+#include "llvm/ConstantHandling.h"
+
+//===----------------------------------------------------------------------===//
+// Local constant propogation...
+//
+
+// ConstantFoldInstruction - If an instruction references constants, try to fold
+// them together...
+//
+bool doConstantPropogation(BasicBlock *BB, BasicBlock::iterator &II) {
+ Instruction *Inst = *II;
+ if (Constant *C = ConstantFoldInstruction(Inst)) {
+ // Replaces all of the uses of a variable with uses of the constant.
+ Inst->replaceAllUsesWith(C);
+
+ // Remove the instruction from the basic block...
+ delete BB->getInstList().remove(II);
+ return true;
+ }
+
+ return false;
+}
+
+// ConstantFoldTerminator - If a terminator instruction is predicated on a
+// constant value, convert it into an unconditional branch to the constant
+// destination.
+//
+bool ConstantFoldTerminator(BasicBlock *BB, BasicBlock::iterator &II,
+ TerminatorInst *T) {
+ // Branch - See if we are conditional jumping on constant
+ if (BranchInst *BI = dyn_cast<BranchInst>(T)) {
+ if (BI->isUnconditional()) return false; // Can't optimize uncond branch
+ BasicBlock *Dest1 = cast<BasicBlock>(BI->getOperand(0));
+ BasicBlock *Dest2 = cast<BasicBlock>(BI->getOperand(1));
+
+ if (ConstantBool *Cond = dyn_cast<ConstantBool>(BI->getCondition())) {
+ // Are we branching on constant?
+ // YES. Change to unconditional branch...
+ BasicBlock *Destination = Cond->getValue() ? Dest1 : Dest2;
+ BasicBlock *OldDest = Cond->getValue() ? Dest2 : Dest1;
+
+ //cerr << "Function: " << T->getParent()->getParent()
+ // << "\nRemoving branch from " << T->getParent()
+ // << "\n\nTo: " << OldDest << endl;
+
+ // Let the basic block know that we are letting go of it. Based on this,
+ // it will adjust it's PHI nodes.
+ assert(BI->getParent() && "Terminator not inserted in block!");
+ OldDest->removePredecessor(BI->getParent());
+
+ // Set the unconditional destination, and change the insn to be an
+ // unconditional branch.
+ BI->setUnconditionalDest(Destination);
+ II = BB->end()-1; // Update instruction iterator!
+ return true;
+ }
+#if 0
+ // FIXME: TODO: This doesn't work if the destination has PHI nodes with
+ // different incoming values on each branch!
+ //
+ else if (Dest2 == Dest1) { // Conditional branch to same location?
+ // This branch matches something like this:
+ // br bool %cond, label %Dest, label %Dest
+ // and changes it into: br label %Dest
+
+ // Let the basic block know that we are letting go of one copy of it.
+ assert(BI->getParent() && "Terminator not inserted in block!");
+ Dest1->removePredecessor(BI->getParent());
+
+ // Change a conditional branch to unconditional.
+ BI->setUnconditionalDest(Dest1);
+ return true;
+ }
+#endif
+ }
+ return false;
+}
+
+
+
+//===----------------------------------------------------------------------===//
+// Local dead code elimination...
+//
+
+bool isInstructionTriviallyDead(Instruction *I) {
+ return I->use_empty() && !I->hasSideEffects() && !isa<TerminatorInst>(I);
+}
+
+// dceInstruction - Inspect the instruction at *BBI and figure out if it's
+// [trivially] dead. If so, remove the instruction and update the iterator
+// to point to the instruction that immediately succeeded the original
+// instruction.
+//
+bool dceInstruction(BasicBlock::InstListType &BBIL,
+ BasicBlock::iterator &BBI) {
+ // Look for un"used" definitions...
+ if (isInstructionTriviallyDead(*BBI)) {
+ delete BBIL.remove(BBI); // Bye bye
+ return true;
+ }
+ return false;
+}