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Implement induction variable injection!

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llvm-svn: 75
This commit is contained in:
Chris Lattner 2001-06-25 07:32:19 +00:00
parent 31e23cdeb4
commit dbdaaef7d5
1 changed files with 76 additions and 12 deletions
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88
llvm/lib/Transforms/Scalar/InductionVars.cpp
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@ -10,6 +10,7 @@
// 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
@ -18,12 +19,14 @@
//
//===----------------------------------------------------------------------===//
#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
@ -151,10 +154,7 @@ static inline bool isSimpleInductionVar(PHINode *PN) {
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!");
@ -180,6 +180,71 @@ static inline bool isSimpleInductionVar(PHINode *PN) {
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:
@ -245,7 +310,7 @@ static bool ProcessInterval(cfg::Interval *Int) {
// 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.
@ -268,9 +333,7 @@ static bool ProcessInterval(cfg::Interval *Int) {
// 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
@ -309,12 +372,13 @@ static bool ProcessInterval(cfg::Interval *Int) {
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.
//
@ -329,13 +393,13 @@ static bool ProcessIntervalPartition(cfg::IntervalPartition &IP) {
// 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;
}
}