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[TTI] BasicTTIImpl assumes no vector registers

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Summary:
Following the discussion on r241884, it's more reasonable to assume that a
target has no vector registers by default instead of letting every such
target overrides getNumberOfRegisters.

Therefore, this patch modifies BasicTTIImpl::getNumberOfRegisters to
return 0 when Vector is true, and partially reverts r241884 which
modifies NVPTXTTIImpl::getNumberOfRegisters.

It also fixes a performance bug in LoopVectorizer. Even if a target has
no vector registers, vectorization may still help ILP. So, we need both
checks to be false before disabling loop vectorization all together.

Reviewers: hfinkel

Subscribers: llvm-commits, jholewinski

Differential Revision: http://reviews.llvm.org/D11108

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241942 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jingyue Wu 2015-07-10 21:14:54 +00:00
parent 01446706b4
commit 020938f3ee
4 changed files with 9 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/llvm/CodeGen/BasicTTIImpl.h
View File

@ -276,7 +276,7 @@ public:
/// \name Vector TTI Implementations
/// @{
unsigned getNumberOfRegisters(bool Vector) { return 1; }
unsigned getNumberOfRegisters(bool Vector) { return Vector ? 0 : 1; }
unsigned getRegisterBitWidth(bool Vector) { return 32; }

6
lib/Target/NVPTX/NVPTXTargetTransformInfo.cpp
View File

@ -117,9 +117,3 @@ unsigned NVPTXTTIImpl::getArithmeticInstrCost(
Opd1PropInfo, Opd2PropInfo);
}
}
unsigned NVPTXTTIImpl::getNumberOfRegisters(bool Vector) {
if (Vector)
return 0;
return BaseT::getNumberOfRegisters(Vector);
}

2
lib/Target/NVPTX/NVPTXTargetTransformInfo.h
View File

@ -58,8 +58,6 @@ public:
TTI::OperandValueKind Opd2Info = TTI::OK_AnyValue,
TTI::OperandValueProperties Opd1PropInfo = TTI::OP_None,
TTI::OperandValueProperties Opd2PropInfo = TTI::OP_None);
unsigned getNumberOfRegisters(bool Vector);
};
} // end namespace llvm

11
lib/Transforms/Vectorize/LoopVectorize.cpp
View File

@ -1456,9 +1456,14 @@ struct LoopVectorize : public FunctionPass {
const BranchProbability ColdProb(1, 5); // 20%
ColdEntryFreq = BlockFrequency(BFI->getEntryFreq()) * ColdProb;
// If the target claims to have no vector registers don't attempt
// vectorization.
if (!TTI->getNumberOfRegisters(true))
// Don't attempt if
// 1. the target claims to have no vector registers, and
// 2. interleaving won't help ILP.
//
// The second condition is necessary because, even if the target has no
// vector registers, loop vectorization may still enable scalar
// interleaving.
if (!TTI->getNumberOfRegisters(true) && TTI->getMaxInterleaveFactor(1) < 2)
return false;
// Build up a worklist of inner-loops to vectorize. This is necessary as