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[Hexagon] Consider zext/sext of a load to i32 to be free

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llvm-svn: 279248
This commit is contained in:
Krzysztof Parzyszek 2016-08-19 14:22:07 +00:00
parent b38195c1a8
commit db019ae801
2 changed files with 27 additions and 0 deletions
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25
llvm/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp
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@ -14,6 +14,7 @@
//===----------------------------------------------------------------------===//
#include "HexagonTargetTransformInfo.h"
#include "llvm/IR/Instructions.h"
#include "llvm/Support/Debug.h"
using namespace llvm;
@ -44,3 +45,27 @@ unsigned HexagonTTIImpl::getPrefetchDistance() const {
unsigned HexagonTTIImpl::getCacheLineSize() const {
return getST()->getL1CacheLineSize();
}
int HexagonTTIImpl::getUserCost(const User *U) {
auto isCastFoldedIntoLoad = [] (const CastInst *CI) -> bool {
if (!CI->isIntegerCast())
return false;
const LoadInst *LI = dyn_cast<const LoadInst>(CI->getOperand(0));
// Technically, this code could allow multiple uses of the load, and
// check if all the uses are the same extension operation, but this
// should be sufficient for most cases.
if (!LI || !LI->hasOneUse())
return false;
// Only extensions from an integer type shorter than 32-bit to i32
// can be folded into the load.
unsigned SBW = CI->getSrcTy()->getIntegerBitWidth();
unsigned DBW = CI->getDestTy()->getIntegerBitWidth();
return DBW == 32 && (SBW < DBW);
};
if (const CastInst *CI = dyn_cast<const CastInst>(U))
if (isCastFoldedIntoLoad(CI))
return TargetTransformInfo::TCC_Free;
return BaseT::getUserCost(U);
}

2
llvm/lib/Target/Hexagon/HexagonTargetTransformInfo.h
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@ -67,6 +67,8 @@ public:
unsigned getNumberOfRegisters(bool vector) const;
/// @}
int getUserCost(const User *U);
};
} // end namespace llvm