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Add a transformation to turn:

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malloc Ty, C
int
  malloc [C x Ty], 1


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@4534 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2002-11-04 16:18:53 +00:00
parent 0eaaa56f1f
commit 0864acf07b
1 changed files with 36 additions and 0 deletions
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36
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -23,6 +23,7 @@
#include "llvm/iPHINode.h"
#include "llvm/iOperators.h"
#include "llvm/Pass.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Support/InstIterator.h"
#include "llvm/Support/InstVisitor.h"
#include "Support/Statistic.h"
@ -76,6 +77,7 @@ namespace {
Instruction *visitCastInst(CastInst &CI);
Instruction *visitPHINode(PHINode &PN);
Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
Instruction *visitAllocationInst(AllocationInst &AI);
// visitInstruction - Specify what to return for unhandled instructions...
Instruction *visitInstruction(Instruction &I) { return 0; }
@ -711,6 +713,40 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
return 0;
}
Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
// Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
if (AI.isArrayAllocation()) // Check C != 1
if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
AllocationInst *New;
// Create and insert the replacement instruction...
if (isa<MallocInst>(AI))
New = new MallocInst(NewTy, 0, AI.getName(), &AI);
else if (isa<AllocaInst>(AI))
New = new AllocaInst(NewTy, 0, AI.getName(), &AI);
// Scan to the end of the allocation instructions, to skip over a block of
// allocas if possible...
//
BasicBlock::iterator It = New;
while (isa<AllocationInst>(*It)) ++It;
// Now that I is pointing to the first non-allocation-inst in the block,
// insert our getelementptr instruction...
//
std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
// Now make everything use the getelementptr instead of the original
// allocation.
ReplaceInstUsesWith(AI, V);
return &AI;
}
return 0;
}
void InstCombiner::removeFromWorkList(Instruction *I) {
WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),