Add a wrapper function to set branch weights metadata.
Summary:
This wrapper checks if there is at least one non-zero weight before
setting the metadata.
Reviewers: davidxl
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D39872
llvm-svn: 317845
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index e0045e9..e26f382 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -776,6 +776,31 @@
return false;
}
+// Set branch weights on SwitchInst. This sets the metadata if there is at
+// least one non-zero weight.
+static void setBranchWeights(SwitchInst *SI, ArrayRef<uint32_t> Weights) {
+ // Check that there is at least one non-zero weight. Otherwise, pass
+ // nullptr to setMetadata which will erase the existing metadata.
+ MDNode *N = nullptr;
+ if (llvm::any_of(Weights, [](uint32_t W) { return W != 0; }))
+ N = MDBuilder(SI->getParent()->getContext()).createBranchWeights(Weights);
+ SI->setMetadata(LLVMContext::MD_prof, N);
+}
+
+// Similar to the above, but for branch and select instructions that take
+// exactly 2 weights.
+static void setBranchWeights(Instruction *I, uint32_t TrueWeight,
+ uint32_t FalseWeight) {
+ assert(isa<BranchInst>(I) || isa<SelectInst>(I));
+ // Check that there is at least one non-zero weight. Otherwise, pass
+ // nullptr to setMetadata which will erase the existing metadata.
+ MDNode *N = nullptr;
+ if (TrueWeight || FalseWeight)
+ N = MDBuilder(I->getParent()->getContext())
+ .createBranchWeights(TrueWeight, FalseWeight);
+ I->setMetadata(LLVMContext::MD_prof, N);
+}
+
/// If TI is known to be a terminator instruction and its block is known to
/// only have a single predecessor block, check to see if that predecessor is
/// also a value comparison with the same value, and if that comparison
@@ -865,9 +890,7 @@
}
}
if (HasWeight && Weights.size() >= 2)
- SI->setMetadata(LLVMContext::MD_prof,
- MDBuilder(SI->getParent()->getContext())
- .createBranchWeights(Weights));
+ setBranchWeights(SI, Weights);
DEBUG(dbgs() << "Leaving: " << *TI << "\n");
return true;
@@ -1172,9 +1195,7 @@
SmallVector<uint32_t, 8> MDWeights(Weights.begin(), Weights.end());
- NewSI->setMetadata(
- LLVMContext::MD_prof,
- MDBuilder(BB->getContext()).createBranchWeights(MDWeights));
+ setBranchWeights(NewSI, MDWeights);
}
EraseTerminatorInstAndDCECond(PTI);
@@ -2738,9 +2759,7 @@
SmallVector<uint32_t, 8> MDWeights(NewWeights.begin(),
NewWeights.end());
- PBI->setMetadata(
- LLVMContext::MD_prof,
- MDBuilder(BI->getContext()).createBranchWeights(MDWeights));
+ setBranchWeights(PBI, MDWeights[0], MDWeights[1]);
} else
PBI->setMetadata(LLVMContext::MD_prof, nullptr);
} else {
@@ -3309,9 +3328,7 @@
// Halve the weights if any of them cannot fit in an uint32_t
FitWeights(NewWeights);
- PBI->setMetadata(LLVMContext::MD_prof,
- MDBuilder(BI->getContext())
- .createBranchWeights(NewWeights[0], NewWeights[1]));
+ setBranchWeights(PBI, NewWeights[0], NewWeights[1]);
}
// OtherDest may have phi nodes. If so, add an entry from PBI's
@@ -3349,9 +3366,7 @@
FitWeights(NewWeights);
- NV->setMetadata(LLVMContext::MD_prof,
- MDBuilder(BI->getContext())
- .createBranchWeights(NewWeights[0], NewWeights[1]));
+ setBranchWeights(NV, NewWeights[0], NewWeights[1]);
}
}
}
@@ -3406,9 +3421,7 @@
// Create a conditional branch sharing the condition of the select.
BranchInst *NewBI = Builder.CreateCondBr(Cond, TrueBB, FalseBB);
if (TrueWeight != FalseWeight)
- NewBI->setMetadata(LLVMContext::MD_prof,
- MDBuilder(OldTerm->getContext())
- .createBranchWeights(TrueWeight, FalseWeight));
+ setBranchWeights(NewBI, TrueWeight, FalseWeight);
}
} else if (KeepEdge1 && (KeepEdge2 || TrueBB == FalseBB)) {
// Neither of the selected blocks were successors, so this
@@ -3594,9 +3607,7 @@
Weights.push_back(Weights[0]);
SmallVector<uint32_t, 8> MDWeights(Weights.begin(), Weights.end());
- SI->setMetadata(
- LLVMContext::MD_prof,
- MDBuilder(SI->getContext()).createBranchWeights(MDWeights));
+ setBranchWeights(SI, MDWeights);
}
}
SI->addCase(Cst, NewBB);
@@ -4323,10 +4334,7 @@
TrueWeight /= 2;
FalseWeight /= 2;
}
- NewBI->setMetadata(LLVMContext::MD_prof,
- MDBuilder(SI->getContext())
- .createBranchWeights((uint32_t)TrueWeight,
- (uint32_t)FalseWeight));
+ setBranchWeights(NewBI, TrueWeight, FalseWeight);
}
}
@@ -4423,9 +4431,7 @@
}
if (HasWeight && Weights.size() >= 2) {
SmallVector<uint32_t, 8> MDWeights(Weights.begin(), Weights.end());
- SI->setMetadata(LLVMContext::MD_prof,
- MDBuilder(SI->getParent()->getContext())
- .createBranchWeights(MDWeights));
+ setBranchWeights(SI, MDWeights);
}
return !DeadCases.empty();