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Handle GEP's a bit more intelligently. Fold constant indices early and

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turn power-of-two multiplies into shifts early to improve compile time.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24253 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-11-09 04:45:33 +00:00
parent 0d902a9c74
commit 7c0104b525
1 changed files with 39 additions and 15 deletions
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54
lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
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@ -32,6 +32,7 @@
#include "llvm/Target/TargetMachine.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Debug.h"
#include <map>
#include <iostream>
@ -607,24 +608,47 @@ void SelectionDAGLowering::visitGetElementPtr(User &I) {
Ty = StTy->getElementType(Field);
} else {
Ty = cast<SequentialType>(Ty)->getElementType();
if (!isa<Constant>(Idx) || !cast<Constant>(Idx)->isNullValue()) {
// N = N + Idx * ElementSize;
uint64_t ElementSize = TD.getTypeSize(Ty);
SDOperand IdxN = getValue(Idx), Scale = getIntPtrConstant(ElementSize);
// If the index is smaller or larger than intptr_t, truncate or extend
// it.
if (IdxN.getValueType() < Scale.getValueType()) {
if (Idx->getType()->isSigned())
IdxN = DAG.getNode(ISD::SIGN_EXTEND, Scale.getValueType(), IdxN);
else
IdxN = DAG.getNode(ISD::ZERO_EXTEND, Scale.getValueType(), IdxN);
} else if (IdxN.getValueType() > Scale.getValueType())
IdxN = DAG.getNode(ISD::TRUNCATE, Scale.getValueType(), IdxN);
// If this is a constant subscript, handle it quickly.
if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx)) {
if (CI->getRawValue() == 0) continue;
IdxN = DAG.getNode(ISD::MUL, N.getValueType(), IdxN, Scale);
N = DAG.getNode(ISD::ADD, N.getValueType(), N, IdxN);
uint64_t Offs;
if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(CI))
Offs = (int64_t)TD.getTypeSize(Ty)*CSI->getValue();
else
Offs = TD.getTypeSize(Ty)*cast<ConstantUInt>(CI)->getValue();
N = DAG.getNode(ISD::ADD, N.getValueType(), N, getIntPtrConstant(Offs));
continue;
}
// N = N + Idx * ElementSize;
uint64_t ElementSize = TD.getTypeSize(Ty);
SDOperand IdxN = getValue(Idx);
// If the index is smaller or larger than intptr_t, truncate or extend
// it.
if (IdxN.getValueType() < N.getValueType()) {
if (Idx->getType()->isSigned())
IdxN = DAG.getNode(ISD::SIGN_EXTEND, N.getValueType(), IdxN);
else
IdxN = DAG.getNode(ISD::ZERO_EXTEND, N.getValueType(), IdxN);
} else if (IdxN.getValueType() > N.getValueType())
IdxN = DAG.getNode(ISD::TRUNCATE, N.getValueType(), IdxN);
// If this is a multiply by a power of two, turn it into a shl
// immediately. This is a very common case.
if (isPowerOf2_64(ElementSize)) {
unsigned Amt = Log2_64(ElementSize);
IdxN = DAG.getNode(ISD::SHL, N.getValueType(), IdxN,
getIntPtrConstant(Amt));
N = DAG.getNode(ISD::ADD, N.getValueType(), N, IdxN);
continue;
}
SDOperand Scale = getIntPtrConstant(ElementSize);
IdxN = DAG.getNode(ISD::MUL, N.getValueType(), IdxN, Scale);
N = DAG.getNode(ISD::ADD, N.getValueType(), N, IdxN);
}
}
setValue(&I, N);