[ADT] Introduce Casting function objects

[mtrofin]

Adding casting function objects as a convenience for expressing e.g. auto AsDoubles = map_range(RangeOfInts, StaticCastTo<double>)​

[mtrofin]

• [ADT] Introduce Casting function objects #165803 👈 (View in Graphite)
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[llvmbot]

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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.

[kuhar]

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

[mtrofin]

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

done, ptal

[kazutakahirata]

LGTM. Let's wait to hear from @kuhar for a day or so.

[kuhar]

The tests can be simplified by casting individual elements instead of combining with map_range.

[mtrofin]

The tests can be simplified by casting individual elements instead of combining with map_range.

True, but I wanted to exercise an example of the targeted use case. WDYT?

[kuhar]

The tests can be simplified by casting individual elements instead of combining with map_range.

True, but I wanted to exercise an example of the targeted use case. WDYT?

We could have that as an extra test case for documentation etc., but otherwise I think it mainly adds complexity we don't need.

[mtrofin]

OK, removed the map_range stuff.

[kuhar]

Looks great