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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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13
lib/Transforms/Scalar/MemCpyOptimizer.cpp
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@@ -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