Prevent unsigned overflow.
The sum of the weights is caculated in an APInt, which has a width smaller than
64. In certain cases, the sum of the widths would overflow when calculations
are done inside an APInt, but would not if done with uint64_t. Since the
values will be passed as uint64_t in the function call anyways, do all the math
in 64 bits. Also added an assert in case the probabilities overflow 64 bits.
llvm-svn: 341444
diff --git a/llvm/lib/Transforms/Instrumentation/ControlHeightReduction.cpp b/llvm/lib/Transforms/Instrumentation/ControlHeightReduction.cpp
index 4da8a71..80e16e7 100644
--- a/llvm/lib/Transforms/Instrumentation/ControlHeightReduction.cpp
+++ b/llvm/lib/Transforms/Instrumentation/ControlHeightReduction.cpp
@@ -614,13 +614,15 @@
ConstantInt *FalseWeight = mdconst::extract<ConstantInt>(MD->getOperand(2));
if (!TrueWeight || !FalseWeight)
return false;
- APInt TrueWt = TrueWeight->getValue();
- APInt FalseWt = FalseWeight->getValue();
- APInt SumWt = TrueWt + FalseWt;
- TrueProb = BranchProbability::getBranchProbability(TrueWt.getZExtValue(),
- SumWt.getZExtValue());
- FalseProb = BranchProbability::getBranchProbability(FalseWt.getZExtValue(),
- SumWt.getZExtValue());
+ uint64_t TrueWt = TrueWeight->getValue().getZExtValue();
+ uint64_t FalseWt = FalseWeight->getValue().getZExtValue();
+ uint64_t SumWt = TrueWt + FalseWt;
+
+ assert(SumWt >= TrueWt && SumWt >= FalseWt &&
+ "Overflow calculating branch probabilities.");
+
+ TrueProb = BranchProbability::getBranchProbability(TrueWt, SumWt);
+ FalseProb = BranchProbability::getBranchProbability(FalseWt, SumWt);
return true;
}