[llvm-commits] CVS: llvm/lib/Analysis/ScalarEvolutionExpander.cpp

[Nate Begeman]

Changes in directory llvm/lib/Analysis:

ScalarEvolutionExpander.cpp added (r1.1)
---
Log message:

Break SCEVExpander out of IndVarSimplify into its own .h/.cpp file so that
other passes may use it.


---
Diffs of the changes:  (+105 -0)

 ScalarEvolutionExpander.cpp |  105 ++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 105 insertions(+)


Index: llvm/lib/Analysis/ScalarEvolutionExpander.cpp
diff -c /dev/null llvm/lib/Analysis/ScalarEvolutionExpander.cpp:1.1
*** /dev/null	Fri Jul 29 19:12:29 2005
--- llvm/lib/Analysis/ScalarEvolutionExpander.cpp	Fri Jul 29 19:12:19 2005
***************
*** 0 ****
--- 1,105 ----
+ //===- ScalarEvolutionExpander.cpp - Scalar Evolution Analysis --*- C++ -*-===//
+ //
+ //                     The LLVM Compiler Infrastructure
+ //
+ // This file was developed by the LLVM research group and is distributed under
+ // the University of Illinois Open Source License. See LICENSE.TXT for details.
+ //
+ //===----------------------------------------------------------------------===//
+ //
+ // This file contains the implementation of the scalar evolution expander,
+ // which is used to generate the code corresponding to a given scalar evolution
+ // expression.
+ //
+ //===----------------------------------------------------------------------===//
+ 
+ #include "llvm/Analysis/LoopInfo.h"
+ #include "llvm/Analysis/ScalarEvolutionExpander.h"
+ using namespace llvm;
+ 
+ Value *SCEVExpander::visitMulExpr(SCEVMulExpr *S) {
+   const Type *Ty = S->getType();
+   int FirstOp = 0;  // Set if we should emit a subtract.
+   if (SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getOperand(0)))
+     if (SC->getValue()->isAllOnesValue())
+       FirstOp = 1;
+ 
+   int i = S->getNumOperands()-2;
+   Value *V = expandInTy(S->getOperand(i+1), Ty);
+ 
+   // Emit a bunch of multiply instructions
+   for (; i >= FirstOp; --i)
+     V = BinaryOperator::createMul(V, expandInTy(S->getOperand(i), Ty),
+                                   "tmp.", InsertPt);
+   // -1 * ...  --->  0 - ...
+   if (FirstOp == 1)
+     V = BinaryOperator::createNeg(V, "tmp.", InsertPt);
+   return V;
+ }
+ 
+ Value *SCEVExpander::visitAddRecExpr(SCEVAddRecExpr *S) {
+   const Type *Ty = S->getType();
+   const Loop *L = S->getLoop();
+   // We cannot yet do fp recurrences, e.g. the xform of {X,+,F} --> X+{0,+,F}
+   assert(Ty->isIntegral() && "Cannot expand fp recurrences yet!");
+ 
+   // {X,+,F} --> X + {0,+,F}
+   if (!isa<SCEVConstant>(S->getStart()) ||
+       !cast<SCEVConstant>(S->getStart())->getValue()->isNullValue()) {
+     Value *Start = expandInTy(S->getStart(), Ty);
+     std::vector<SCEVHandle> NewOps(S->op_begin(), S->op_end());
+     NewOps[0] = SCEVUnknown::getIntegerSCEV(0, Ty);
+     Value *Rest = expandInTy(SCEVAddRecExpr::get(NewOps, L), Ty);
+ 
+     // FIXME: look for an existing add to use.
+     return BinaryOperator::createAdd(Rest, Start, "tmp.", InsertPt);
+   }
+ 
+   // {0,+,1} --> Insert a canonical induction variable into the loop!
+   if (S->getNumOperands() == 2 &&
+       S->getOperand(1) == SCEVUnknown::getIntegerSCEV(1, Ty)) {
+     // Create and insert the PHI node for the induction variable in the
+     // specified loop.
+     BasicBlock *Header = L->getHeader();
+     PHINode *PN = new PHINode(Ty, "indvar", Header->begin());
+     PN->addIncoming(Constant::getNullValue(Ty), L->getLoopPreheader());
+ 
+     pred_iterator HPI = pred_begin(Header);
+     assert(HPI != pred_end(Header) && "Loop with zero preds???");
+     if (!L->contains(*HPI)) ++HPI;
+     assert(HPI != pred_end(Header) && L->contains(*HPI) &&
+            "No backedge in loop?");
+ 
+     // Insert a unit add instruction right before the terminator corresponding
+     // to the back-edge.
+     Constant *One = Ty->isFloatingPoint() ? (Constant*)ConstantFP::get(Ty, 1.0)
+                                           : ConstantInt::get(Ty, 1);
+     Instruction *Add = BinaryOperator::createAdd(PN, One, "indvar.next",
+                                                  (*HPI)->getTerminator());
+ 
+     pred_iterator PI = pred_begin(Header);
+     if (*PI == L->getLoopPreheader())
+       ++PI;
+     PN->addIncoming(Add, *PI);
+     return PN;
+   }
+ 
+   // Get the canonical induction variable I for this loop.
+   Value *I = getOrInsertCanonicalInductionVariable(L, Ty);
+ 
+   if (S->getNumOperands() == 2) {   // {0,+,F} --> i*F
+     Value *F = expandInTy(S->getOperand(1), Ty);
+     return BinaryOperator::createMul(I, F, "tmp.", InsertPt);
+   }
+ 
+   // If this is a chain of recurrences, turn it into a closed form, using the
+   // folders, then expandCodeFor the closed form.  This allows the folders to
+   // simplify the expression without having to build a bunch of special code
+   // into this folder.
+   SCEVHandle IH = SCEVUnknown::get(I);   // Get I as a "symbolic" SCEV.
+ 
+   SCEVHandle V = S->evaluateAtIteration(IH);
+   //std::cerr << "Evaluated: " << *this << "\n     to: " << *V << "\n";
+ 
+   return expandInTy(V, Ty);
+ }