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[NFC] Generalize the arithmetic type for getDisjunctionWeights #167593

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Merged
merged 1 commit into from
Nov 12, 2025
+10 −4
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[NFC] Generalize the arithmetic type for getDisjunctionWeights #167593

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14 changes: 10 additions & 4 deletions llvm/include/llvm/IR/ProfDataUtils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,8 @@
#include "llvm/ADT/SmallVector.h"
#include "llvm/IR/Metadata.h"
#include "llvm/Support/Compiler.h"
#include <cstddef>
#include <type_traits>

namespace llvm {
struct MDProfLabels {
Expand Down Expand Up @@ -216,9 +218,13 @@ LLVM_ABI void scaleProfData(Instruction &I, uint64_t S, uint64_t T);
/// branch weights B1 and B2, respectively. In both B1 and B2, the first
/// position (index 0) is for the 'true' branch, and the second position (index
/// 1) is for the 'false' branch.
template <typename T1, typename T2,
typename = typename std::enable_if<
std::is_arithmetic_v<T1> && std::is_arithmetic_v<T2> &&
sizeof(T1) <= sizeof(uint64_t) && sizeof(T2) <= sizeof(uint64_t)>>
inline SmallVector<uint64_t, 2>
getDisjunctionWeights(const SmallVector<uint32_t, 2> &B1,
const SmallVector<uint32_t, 2> &B2) {
getDisjunctionWeights(const SmallVector<T1, 2> &B1,
const SmallVector<T2, 2> &B2) {
// For the first conditional branch, the probability the "true" case is taken
// is p(b1) = B1[0] / (B1[0] + B1[1]). The "false" case's probability is
// p(not b1) = B1[1] / (B1[0] + B1[1]).
Expand All @@ -235,8 +241,8 @@ getDisjunctionWeights(const SmallVector<uint32_t, 2> &B1,
// the product of sums, the subtracted one cancels out).
assert(B1.size() == 2);
assert(B2.size() == 2);
auto FalseWeight = B1[1] * B2[1];
auto TrueWeight = B1[0] * B2[0] + B1[0] * B2[1] + B1[1] * B2[0];
uint64_t FalseWeight = B1[1] * B2[1];
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@boomanaiden154 boomanaiden154 Nov 12, 2025

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What's the motivation for changing this? Previously it would default to the integer type, but now it's fixed.

Shouldn't be a big issue for uint64_t specifically, but maybe a good idea to add a static assert that the bit width of T1/T2 is less than or equal to 64?

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@mtrofin mtrofin Nov 12, 2025

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to avoid overflow. I missed the fact I should have declared it uint64_t explicitly the first time around.

added static asserts.

uint64_t TrueWeight = B1[0] * (B2[0] + B2[1]) + B1[1] * B2[0];
return {TrueWeight, FalseWeight};
}
} // namespace llvm
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