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Handle a common case more carefully. In particular, instead of transforming 

pointer recurrences into expressions from this:

  %P_addr.0.i.0 = phi sbyte* [ getelementptr ([8 x sbyte]* %.str_1, int 0, int 0), %entry ], [ %inc.0.i, %no_exit.i ]
  %inc.0.i = getelementptr sbyte* %P_addr.0.i.0, int 1            ; <sbyte*> [#uses=2]

into this:

  %inc.0.i = getelementptr sbyte* getelementptr ([8 x sbyte]* %.str_1, int 0, int 0), int %inc.0.i.rec

Actually create something nice, like this:

  %inc.0.i = getelementptr [8 x sbyte]* %.str_1, int 0, int %inc.0.i.rec

llvm-svn: 16924
This commit is contained in:
Chris Lattner 2004-10-11 23:06:50 +00:00
parent 13128ab8fb
commit 9776f7259b
1 changed files with 33 additions and 4 deletions
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37
llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
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@ -45,6 +45,7 @@
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/ADT/Statistic.h"
@ -135,9 +136,9 @@ namespace {
while (isa<PHINode>(It)) ++It;
if (It != BasicBlock::iterator(CI)) {
// Splice the cast immediately after the operand in question.
I->getParent()->getInstList().splice(It,
CI->getParent()->getInstList(),
CI);
BasicBlock::InstListType &InstList =
I->getParent()->getInstList();
InstList.splice(It, InstList, CI);
}
return CI;
}
@ -345,7 +346,7 @@ DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts) {
if (Instruction *U = dyn_cast<Instruction>(I->getOperand(i)))
Insts.insert(U);
SE->deleteInstructionFromRecords(I);
I->getParent()->getInstList().erase(I);
I->eraseFromParent();
Changed = true;
}
}
@ -387,6 +388,34 @@ void IndVarSimplify::EliminatePointerRecurrence(PHINode *PN,
// Update the GEP to use the new recurrence we just inserted.
GEPI->setOperand(1, NewAdd);
// If the incoming value is a constant expr GEP, try peeling out the array
// 0 index if possible to make things simpler.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEPI->getOperand(0)))
if (CE->getOpcode() == Instruction::GetElementPtr) {
unsigned NumOps = CE->getNumOperands();
assert(NumOps > 1 && "CE folding didn't work!");
if (CE->getOperand(NumOps-1)->isNullValue()) {
// Check to make sure the last index really is an array index.
gep_type_iterator GTI = gep_type_begin(GEPI);
for (unsigned i = 1, e = GEPI->getNumOperands()-1;
i != e; ++i, ++GTI)
/*empty*/;
if (isa<SequentialType>(*GTI)) {
// Pull the last index out of the constant expr GEP.
std::vector<Value*> CEIdxs(CE->op_begin()+1, CE->op_end()-1);
Constant *NCE = ConstantExpr::getGetElementPtr(CE->getOperand(0),
CEIdxs);
GetElementPtrInst *NGEPI =
new GetElementPtrInst(NCE, Constant::getNullValue(Type::IntTy),
NewAdd, GEPI->getName(), GEPI);
GEPI->replaceAllUsesWith(NGEPI);
GEPI->eraseFromParent();
GEPI = NGEPI;
}
}
}
// Finally, if there are any other users of the PHI node, we must
// insert a new GEP instruction that uses the pre-incremented version
// of the induction amount.