[flang] Implement the runtime portion of the UNPACK intrinsic

[PeteSteinfeld]

Summary

I'd previously merged this into the fir-dev branch. This change is to
do the same thing to the main branch of llvm-project.

[mleair]

flang/runtime/transformational.cpp

524

Same comment as before. llvm style does not like braces for single code blocks.

[PeteSteinfeld]

flang/runtime/transformational.cpp

524

And as I mentioned in the other pull request, I don't think we're following this convention for flang code.

[mleair]

flang/runtime/transformational.cpp

524

Saw you comment in your cshift review. So, disregard.

[jeanPerier]

flang/runtime/transformational.cpp

524

It looks ok to me to have it the way you changed it, but I am surprised you had to change it. Isn't field.IncrementSubscripts(fieldAt) a no-op on scalar field ? Did you run into bugs without your change ?

[PeteSteinfeld]

flang/runtime/transformational.cpp

524

This is weird. I thought I had a test that failed without this change, but I just tried to reproduce it, and I can't. So I'll revert the code.

[PeteSteinfeld]

Responding to review comments.

[jeanPerier]

LGTM

flang/runtime/transformational.cpp

if (IsLogicalElementTrue(mask, maskAt)) {
       }
       CopyElement(result, resultAt, vector, &vectorAt, terminator);
       ++vectorAt;
     } else {
       CopyElement(result, resultAt, field, fieldAt, terminator);
     }
     result.IncrementSubscripts(resultAt);
     mask.IncrementSubscripts(maskAt);
+    if (field.rank() != 0) { // scalar "field" argument
       field.IncrementSubscripts(fieldAt);
     }
   }
+}
 
 } // extern "C"
 } // namespace Fortran::runtime

flang/unittests/RuntimeGTest/Transformational.cpp

TEST(Transformational, Unpack) {
   EXPECT_EQ(result.GetDimension(0).Extent(), 2);
   EXPECT_EQ(result.GetDimension(1).LowerBound(), 1);
   EXPECT_EQ(result.GetDimension(1).Extent(), 3);
   static std::int32_t expect[6]{-1, 1, 2, -4, -5, 3};
   for (int j{0}; j < 6; ++j) {
     EXPECT_EQ(*result.ZeroBasedIndexedElement<std::int32_t>(j), expect[j]);
   }
   result.Destroy();
+
+  // Test for scalar value of the "field" argument
+  auto scalarField{MakeArray<TypeCategory::Integer, 4>(
+      std::vector<int>{}, std::vector<std::int32_t>{343})};
+  RTNAME(Unpack)(result, *vector, *mask, *scalarField, __FILE__, __LINE__);
+  EXPECT_EQ(result.rank(), 2);
+  EXPECT_EQ(result.GetDimension(0).LowerBound(), 1);
+  EXPECT_EQ(result.GetDimension(0).Extent(), 2);
+  EXPECT_EQ(result.GetDimension(1).LowerBound(), 1);
+  EXPECT_EQ(result.GetDimension(1).Extent(), 3);
+  static std::int32_t scalarExpect[6]{343, 1, 2, 343, 343, 3};
+  for (int j{0}; j < 6; ++j) {
+    EXPECT_EQ(
+        *result.ZeroBasedIndexedElement<std::int32_t>(j), scalarExpect[j]);
+  }
+  result.Destroy();
 }