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MemCpyOptimizer: Use max legal int size instead of pointer size

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If there are no legal integers, assume 1 byte.

This makes more sense than using the pointer size as
a guess for the maximum GPR width.

It is conceivable to want to use some 64-bit pointers
on a target where 64-bit integers aren't legal.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190817 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Matt Arsenault 2013-09-16 22:43:16 +00:00
parent 0c190ad93f
commit 4b28ee2088
3 changed files with 26 additions and 5 deletions
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11
include/llvm/IR/DataLayout.h
View File

@ -369,6 +369,17 @@ public:
/// least as big as Width bits.
Type *getSmallestLegalIntType(LLVMContext &C, unsigned Width = 0) const;
/// getLargestLegalIntType - Return the largest legal integer type, or null if
/// none are set.
Type *getLargestLegalIntType(LLVMContext &C) const {
unsigned LargestSize = getLargestLegalIntTypeSize();
return (LargestSize == 0) ? 0 : Type::getIntNTy(C, LargestSize);
}
/// getLargestLegalIntType - Return the size of largest legal integer type
/// size, or 0 if none are set.
unsigned getLargestLegalIntTypeSize() const;
/// getIndexedOffset - return the offset from the beginning of the type for
/// the specified indices. This is used to implement getelementptr.
uint64_t getIndexedOffset(Type *Ty, ArrayRef<Value *> Indices) const;

7
lib/IR/DataLayout.cpp
View File

@ -629,6 +629,13 @@ Type *DataLayout::getSmallestLegalIntType(LLVMContext &C, unsigned Width) const
return 0;
}
unsigned DataLayout::getLargestLegalIntTypeSize() const {
unsigned MaxWidth = 0;
for (unsigned i = 0, e = (unsigned)LegalIntWidths.size(); i != e; ++i)
MaxWidth = std::max<unsigned>(MaxWidth, LegalIntWidths[i]);
return MaxWidth;
}
uint64_t DataLayout::getIndexedOffset(Type *ptrTy,
ArrayRef<Value *> Indices) const {
Type *Ty = ptrTy;

13
lib/Transforms/Scalar/MemCpyOptimizer.cpp
View File

@ -170,14 +170,17 @@ bool MemsetRange::isProfitableToUseMemset(const DataLayout &TD) const {
// pessimize the llvm optimizer.
//
// Since we don't have perfect knowledge here, make some assumptions: assume
// the maximum GPR width is the same size as the pointer size and assume that
// this width can be stored. If so, check to see whether we will end up
// actually reducing the number of stores used.
// the maximum GPR width is the same size as the largest legal integer
// size. If so, check to see whether we will end up actually reducing the
// number of stores used.
unsigned Bytes = unsigned(End-Start);
unsigned NumPointerStores = Bytes/TD.getPointerSize();
unsigned MaxIntSize = TD.getLargestLegalIntTypeSize();
if (MaxIntSize == 0)
MaxIntSize = 1;
unsigned NumPointerStores = Bytes / MaxIntSize;
// Assume the remaining bytes if any are done a byte at a time.
unsigned NumByteStores = Bytes - NumPointerStores*TD.getPointerSize();
unsigned NumByteStores = Bytes - NumPointerStores * MaxIntSize;
// If we will reduce the # stores (according to this heuristic), do the
// transformation. This encourages merging 4 x i8 -> i32 and 2 x i16 -> i32