// Header block, allowing it to be found easily.
// - All other preexisting induction variables are adjusted to operate in
// terms of this primary induction variable
+// - Induction variables with a step size of 0 have been eliminated.
//
// This code assumes the following is true to perform its full job:
// - The CFG has been simplified to not have multiple entrances into an
//
//===----------------------------------------------------------------------===//
+#include "llvm/Opt/AllOpts.h"
#include "llvm/ConstPoolVals.h"
#include "llvm/Analysis/IntervalPartition.h"
-#include "llvm/Opt/AllOpts.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/Tools/STLExtras.h"
+#include "llvm/SymbolTable.h"
#include "llvm/iOther.h"
+#include "llvm/CFG.h"
#include <algorithm>
// isLoopInvariant - Return true if the specified value/basic block source is
return false; // Not signed or unsigned? Must be FP type or something
}
- // How do I check for 0 for any integral value? Use
- // ConstPoolVal::getNullConstant?
-
- Value *StepExpr = PN->getIncomingValue(1);
+ Value *StepExpr = PN->getIncomingValue(1);
assert(StepExpr->getValueType() == Value::InstructionVal && "No ADD node?");
assert(((Instruction*)StepExpr)->getInstType() == Instruction::Add &&
"No ADD node? Not a cannonical PHI!");
return true;
}
+// InjectSimpleInductionVariable - Insert a cannonical induction variable into
+// the interval header Header. This assumes that the flow graph is in
+// simplified form (so we know that the header block has exactly 2 predecessors)
+//
+// TODO: This should inherit the largest type that is being used by the already
+// present induction variables (instead of always using uint)
+//
+static PHINode *InjectSimpleInductionVariable(cfg::Interval *Int) {
+ string PHIName, AddName;
+
+ BasicBlock *Header = Int->getHeaderNode();
+ Method *M = Header->getParent();
+
+ if (M->hasSymbolTable()) {
+ // Only name the induction variable if the method isn't stripped.
+ PHIName = M->getSymbolTable()->getUniqueName(Type::UIntTy, "ind_var");
+ AddName = M->getSymbolTable()->getUniqueName(Type::UIntTy, "ind_var_next");
+ }
+
+ // Create the neccesary instructions...
+ PHINode *PN = new PHINode(Type::UIntTy, PHIName);
+ ConstPoolVal *One = new ConstPoolUInt(Type::UIntTy, 1);
+ ConstPoolVal *Zero = new ConstPoolUInt(Type::UIntTy, 0);
+ BinaryOperator *AddNode = BinaryOperator::create(Instruction::Add,
+ PN, One, AddName);
+
+ // Figure out which predecessors I have to play with... there should be
+ // exactly two... one of which is a loop predecessor, and one of which is not.
+ //
+ cfg::pred_iterator PI = cfg::pred_begin(Header);
+ assert(PI != cfg::pred_end(Header) && "Header node should have 2 preds!");
+ BasicBlock *Pred1 = *PI; ++PI;
+ assert(PI != cfg::pred_end(Header) && "Header node should have 2 preds!");
+ BasicBlock *Pred2 = *PI;
+ assert(++PI == cfg::pred_end(Header) && "Header node should have 2 preds!");
+
+ // Make Pred1 be the loop entrance predecessor, Pred2 be the Loop predecessor
+ if (Int->contains(Pred1)) swap(Pred1, Pred2);
+
+ assert(!Int->contains(Pred1) && "Pred1 should be loop entrance!");
+ assert( Int->contains(Pred2) && "Pred2 should be looping edge!");
+
+ // Link the instructions into the PHI node...
+ PN->addIncoming(Zero, Pred1); // The initializer is first argument
+ PN->addIncoming(AddNode, Pred2); // The step size is second PHI argument
+
+ // Insert the PHI node into the Header of the loop. It shall be the first
+ // instruction, because the "Simple" Induction Variable must be first in the
+ // block.
+ //
+ BasicBlock::InstListType &IL = Header->getInstList();
+ IL.push_front(PN);
+
+ // Insert the Add instruction as the first (non-phi) instruction in the
+ // header node's basic block.
+ BasicBlock::InstListType::iterator I = IL.begin();
+ while ((*I)->isPHINode()) ++I;
+ IL.insert(I, AddNode);
+
+ // Insert the constants into the constant pool for the method...
+ M->getConstantPool().insert(One);
+ M->getConstantPool().insert(Zero);
+ return PN;
+}
+
// ProcessInterval - This function is invoked once for each interval in the
// IntervalPartition of the program. It looks for auxilliary induction
// variables in loops. If it finds one, it:
// anything about BB2/V2. Check now to see if V2 is a linear induction
// variable.
//
- cerr << "Found loop invariant computation: " << V1;
+ cerr << "Found loop invariant computation: " << V1 << endl;
if (!isLinearInductionVariable(Int, V2, PN))
continue; // No, it is not a linear ind var, ignore the PHI node.
// A simple induction variable was not found, inject one now...
if (It == InductionVars.end()) {
- cerr << "WARNING, Induction variable injection not implemented yet!\n";
- // TODO: Inject induction variable
- PrimaryIndVar = 0; // Point it at the new indvar
+ PrimaryIndVar = InjectSimpleInductionVariable(Int);
} else {
// Move the PHI node for this induction variable to the start of the PHI
// list in HeaderNode... we do not need to do this for the inserted case
static bool ProcessIntervalPartition(cfg::IntervalPartition &IP) {
// This currently just prints out information about the interval structure
// of the method...
+#if 0
static unsigned N = 0;
cerr << "\n***********Interval Partition #" << (++N) << "************\n\n";
copy(IP.begin(), IP.end(), ostream_iterator<cfg::Interval*>(cerr, "\n"));
cerr << "\n*********** PERFORMING WORK ************\n\n";
-
+#endif
// Loop over all of the intervals in the partition and look for induction
// variables in intervals that represent loops.
//
// until the graph is gone.
//
bool DoInductionVariableCannonicalize(Method *M) {
- if (1) { // Print basic blocks with their depth
+ // TODO: REMOVE
+ if (0) { // Print basic blocks with their depth
LoopDepthCalculator LDC(M);
for (Method::iterator I = M->getBasicBlocks().begin();
I != M->getBasicBlocks().end(); ++I) {
cerr << "Basic Block Depth: " << LDC.getLoopDepth(*I) << *I;
}
-
}
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