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[ADT] Introduce a static_cast_to #165803

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[ADT] Introduce a static_cast_to #165803

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5 changes: 5 additions & 0 deletions llvm/include/llvm/ADT/STLExtras.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1704,6 +1704,11 @@ auto sum_of(R &&Range, E Init = E{0}) {
return accumulate(std::forward<R>(Range), std::move(Init));
}

/// Returns a range where each value of `R` is static_cast to `T`
template <typename T, typename R> auto static_cast_to(R &&Range) {
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I think the idea makes sense but I wonder if we could pick a more descriptive function name, similar to other range functions

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@kuhar kuhar Oct 31, 2025 •
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One alternative would be not to add a range function and instead lift static cast to a function object like we did for llvm::IsaPred<T>. This way we can support variants based on dyn_cast/dyn_cast_if_present/cast.

I think that's a more general solution that composes with other functions like map_to_vector

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How would the usage look like?

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@kuhar kuhar Oct 31, 2025 •
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map_range(Foo, StaticCastTo<unsigned>)
map_range(Bar, DynCastTo<IntegerAttr>)
map_to_vector(Baz, CastTo<FloatType>)

return map_range(Range, [](const auto &V) { return static_cast<T>(V); });
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@zwuis zwuis Oct 31, 2025 •
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[](auto &V) -> decltype(auto) { return static_cast<T>(V); }

Perhaps -> decltype(auto) is needed to allow returning reference.

}

/// Returns the product of all values in `Range` with `Init` initial value.
/// The default initial value is 1.
template <typename R, typename E = detail::ValueOfRange<R>>
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7 changes: 7 additions & 0 deletions llvm/unittests/ADT/STLExtrasTest.cpp
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Expand Up @@ -1669,6 +1669,13 @@ TEST(STLExtrasTest, SumOf) {
EXPECT_EQ(sum_of(V3), 3.0f);
}

TEST(STLExtrasTest, StaticCastTo) {
std::vector<int32_t> R{1, 2, 3};
EXPECT_TRUE(all_of(R, [](auto V) { return sizeof(V) == sizeof(int32_t); }));
EXPECT_TRUE(all_of(static_cast_to<int64_t>(R),
[](auto V) { return sizeof(V) == sizeof(int64_t); }));
}

TEST(STLExtrasTest, ProductOf) {
EXPECT_EQ(product_of(std::vector<int>()), 1);
EXPECT_EQ(product_of(std::vector<int>(), 0), 0);
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