[ADT] Introduce a static_cast_to

[mtrofin]

Adding a static_cast_to​ over a range as a convenience.

[mtrofin]

• [ADT] Introduce a static_cast_to #165803 👈 (View in Graphite)
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[llvmbot]

@llvm/pr-subscribers-llvm-adt

Author: Mircea Trofin (mtrofin)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/165803.diff

2 Files Affected:

• (modified) llvm/include/llvm/ADT/STLExtras.h (+6)
• (modified) llvm/unittests/ADT/STLExtrasTest.cpp (+7)

diff --git a/llvm/include/llvm/ADT/STLExtras.h b/llvm/include/llvm/ADT/STLExtras.h
index a9841c6651b72..f65d08cafbdc6 100644
--- a/llvm/include/llvm/ADT/STLExtras.h
+++ b/llvm/include/llvm/ADT/STLExtras.h
@@ -1704,6 +1704,12 @@ auto sum_of(R &&Range, E Init = E{0}) {
   return accumulate(std::forward<R>(Range), std::move(Init));
 }
 
+/// Return a range where each value of `R` is static_cast to `T`
+template <typename T, typename R>
+auto static_cast_to(R &&Range) {
+  return map_range(Range, [](const auto &V) { return static_cast<T>(V); });
+}
+
 /// 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>>
diff --git a/llvm/unittests/ADT/STLExtrasTest.cpp b/llvm/unittests/ADT/STLExtrasTest.cpp
index 966b1f01e8a31..f9341dd64c999 100644
--- a/llvm/unittests/ADT/STLExtrasTest.cpp
+++ b/llvm/unittests/ADT/STLExtrasTest.cpp
@@ -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);

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[zwuis]

[](auto &V) -> decltype(auto) { return static_cast<T>(V); }

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

[kuhar]

I think the idea makes sense but I wonder if we could pick a more descriptive function name, similar to other range functions

[kuhar]

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

[mtrofin]

How would the usage look like?

[kuhar]

map_range(Foo, StaticCastTo<unsigned>)
map_range(Bar, DynCastTo<IntegerAttr>)
map_to_vector(Baz, CastTo<FloatType>)

[kuhar]

Cast function objects similar to IsaPred seem like a more general direction