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Reuse the logic in getEdgeProbability within getHotSucc in order to

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correctly handle blocks whose successor weights sum to more than
UINT32_MAX. This is slightly less efficient, but the entire thing is
already linear on the number of successors. Calling it within any hot
routine is a mistake, and indeed no one is calling it. It also
simplifies the code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144527 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth 2011-11-14 08:55:59 +00:00
parent 2770c14185
commit c4e1562825
2 changed files with 4 additions and 11 deletions
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1
include/llvm/CodeGen/MachineBranchProbabilityInfo.h
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@ -59,6 +59,7 @@ public:
bool isEdgeHot(MachineBasicBlock *Src, MachineBasicBlock *Dst) const;
// Return a hot successor for the block BB or null if there isn't one.
// NB: This routine's complexity is linear on the number of successors.
MachineBasicBlock *getHotSucc(MachineBasicBlock *MBB) const;
// Return a probability as a fraction between 0 (0% probability) and

14
lib/CodeGen/MachineBranchProbabilityInfo.cpp
View File

@ -76,26 +76,18 @@ bool MachineBranchProbabilityInfo::isEdgeHot(MachineBasicBlock *Src,
MachineBasicBlock *
MachineBranchProbabilityInfo::getHotSucc(MachineBasicBlock *MBB) const {
uint32_t Sum = 0;
uint32_t MaxWeight = 0;
MachineBasicBlock *MaxSucc = 0;
for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
E = MBB->succ_end(); I != E; ++I) {
MachineBasicBlock *Succ = *I;
uint32_t Weight = getEdgeWeight(MBB, Succ);
uint32_t PrevSum = Sum;
Sum += Weight;
assert(Sum > PrevSum); (void) PrevSum;
uint32_t Weight = getEdgeWeight(MBB, *I);
if (Weight > MaxWeight) {
MaxWeight = Weight;
MaxSucc = Succ;
MaxSucc = *I;
}
}
if (BranchProbability(MaxWeight, Sum) >= BranchProbability(4, 5))
if (getEdgeProbability(MBB, MaxSucc) >= BranchProbability(4, 5))
return MaxSucc;
return 0;