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Allow constants of different types to share constant pool entries

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if they have compatible encodings.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85359 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2009-10-28 01:12:16 +00:00
parent c5a75523ef
commit 83f6120c9a
2 changed files with 66 additions and 3 deletions
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50
lib/CodeGen/MachineFunction.cpp
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@ -581,6 +581,47 @@ MachineConstantPool::~MachineConstantPool() {
delete Constants[i].Val.MachineCPVal;
}
/// CanShareConstantPoolEntry - Test whether the given two constants
/// can be allocated the same constant pool entry.
static bool CanShareConstantPoolEntry(Constant *A, Constant *B,
const TargetData *TD) {
// Handle the trivial case quickly.
if (A == B) return true;
// If they have the same type but weren't the same constant, quickly
// reject them.
if (A->getType() == B->getType()) return false;
// For now, only support constants with the same size.
if (TD->getTypeStoreSize(A->getType()) != TD->getTypeStoreSize(B->getType()))
return false;
// If a floating-point value and an integer value have the same encoding,
// they can share a constant-pool entry.
if (ConstantFP *AFP = dyn_cast<ConstantFP>(A))
if (ConstantInt *BI = dyn_cast<ConstantInt>(B))
return AFP->getValueAPF().bitcastToAPInt() == BI->getValue();
if (ConstantFP *BFP = dyn_cast<ConstantFP>(B))
if (ConstantInt *AI = dyn_cast<ConstantInt>(A))
return BFP->getValueAPF().bitcastToAPInt() == AI->getValue();
// Two vectors can share an entry if each pair of corresponding
// elements could.
if (ConstantVector *AV = dyn_cast<ConstantVector>(A))
if (ConstantVector *BV = dyn_cast<ConstantVector>(B)) {
if (AV->getType()->getNumElements() != BV->getType()->getNumElements())
return false;
for (unsigned i = 0, e = AV->getType()->getNumElements(); i != e; ++i)
if (!CanShareConstantPoolEntry(AV->getOperand(i), BV->getOperand(i), TD))
return false;
return true;
}
// TODO: Handle other cases.
return false;
}
/// getConstantPoolIndex - Create a new entry in the constant pool or return
/// an existing one. User must specify the log2 of the minimum required
/// alignment for the object.
@ -589,14 +630,17 @@ unsigned MachineConstantPool::getConstantPoolIndex(Constant *C,
unsigned Alignment) {
assert(Alignment && "Alignment must be specified!");
if (Alignment > PoolAlignment) PoolAlignment = Alignment;
// Check to see if we already have this constant.
//
// FIXME, this could be made much more efficient for large constant pools.
for (unsigned i = 0, e = Constants.size(); i != e; ++i)
if (Constants[i].Val.ConstVal == C &&
(Constants[i].getAlignment() & (Alignment - 1)) == 0)
if (!Constants[i].isMachineConstantPoolEntry() &&
CanShareConstantPoolEntry(Constants[i].Val.ConstVal, C, TD)) {
if ((unsigned)Constants[i].getAlignment() < Alignment)
Constants[i].Alignment = Alignment;
return i;
}
Constants.push_back(MachineConstantPoolEntry(C, Alignment));
return Constants.size()-1;