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Use getEdgeProbability() instead of getEdgeWeight() in BFI and remove getEdgeWeight() interfaces from MBPI.

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This patch removes all getEdgeWeight() interfaces from CodeGen directory. As
getEdgeProbability() is a little more expensive than getEdgeWeight(), I will
compose a patch soon in which BPI only stores probabilities instead of edge
weights so that getEdgeProbability() will have O(1) time.


Differential revision: http://reviews.llvm.org/D15489

llvm-svn: 256039
This commit is contained in:
Cong Hou 2015-12-18 21:53:24 +00:00
parent 76a12162c8
commit d24cdaa414
4 changed files with 10 additions and 28 deletions
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11
include/llvm/Analysis/BlockFrequencyInfoImpl.h
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@ -1173,6 +1173,13 @@ void BlockFrequencyInfoImpl<BT>::computeIrreducibleMass(
updateLoopWithIrreducible(*OuterLoop);
}
namespace {
// A helper function that converts a branch probability into weight.
inline uint32_t getWeightFromBranchProb(const BranchProbability Prob) {
return Prob.getNumerator();
}
} // namespace
template <class BT>
bool
BlockFrequencyInfoImpl<BT>::propagateMassToSuccessors(LoopData *OuterLoop,
@ -1189,10 +1196,8 @@ BlockFrequencyInfoImpl<BT>::propagateMassToSuccessors(LoopData *OuterLoop,
const BlockT *BB = getBlock(Node);
for (auto SI = Successor::child_begin(BB), SE = Successor::child_end(BB);
SI != SE; ++SI)
// Do not dereference SI, or getEdgeWeight() is linear in the number of
// successors.
if (!addToDist(Dist, OuterLoop, Node, getNode(*SI),
BPI->getEdgeWeight(BB, SI)))
getWeightFromBranchProb(BPI->getEdgeProbability(BB, SI))))
// Irreducible backedge.
return false;
}

10
include/llvm/CodeGen/MachineBranchProbabilityInfo.h
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@ -45,16 +45,6 @@ public:
AU.setPreservesAll();
}
// Return edge weight. If we don't have any informations about it - return
// DEFAULT_WEIGHT.
uint32_t getEdgeWeight(const MachineBasicBlock *Src,
const MachineBasicBlock *Dst) const;
// Same thing, but using a const_succ_iterator from Src. This is faster when
// the iterator is already available.
uint32_t getEdgeWeight(const MachineBasicBlock *Src,
MachineBasicBlock::const_succ_iterator Dst) const;
// Return edge probability.
BranchProbability getEdgeProbability(const MachineBasicBlock *Src,
const MachineBasicBlock *Dst) const;

13
lib/CodeGen/MachineBranchProbabilityInfo.cpp
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@ -28,19 +28,6 @@ char MachineBranchProbabilityInfo::ID = 0;
void MachineBranchProbabilityInfo::anchor() { }
uint32_t MachineBranchProbabilityInfo::getEdgeWeight(
const MachineBasicBlock *Src,
MachineBasicBlock::const_succ_iterator Dst) const {
return Src->getSuccProbability(Dst).getNumerator();
}
uint32_t MachineBranchProbabilityInfo::getEdgeWeight(
const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const {
// This is a linear search. Try to use the const_succ_iterator version when
// possible.
return getEdgeWeight(Src, std::find(Src->succ_begin(), Src->succ_end(), Dst));
}
BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
const MachineBasicBlock *Src,
MachineBasicBlock::const_succ_iterator Dst) const {

4
test/Analysis/BlockFrequencyInfo/bad_input.ll
View File

@ -9,8 +9,8 @@ define void @branch_weight_0(i32 %a) {
entry:
br label %for.body
; Check that we get 1,4 instead of 0,3.
; CHECK-NEXT: for.body: float = 4.0,
; Check that we get 1 and a huge frequency instead of 0,3.
; CHECK-NEXT: for.body: float = 2147483647.8,
for.body:
%i = phi i32 [ 0, %entry ], [ %inc, %for.body ]
call void @g(i32 %i)