[Support] Add format object for interleaved ranges (#135517)

Add two new format functions for printing ranges: `interleaved` and
`interleaved_array`.

This is meant to improve the ergonomics of printing ranges. Before this
patch, we have to either use `llvm::interleave` or write a for loop by
hand. For example:

Before:
```c++
ArrayRef<Type> types = ...;
ArrayRef<Values> values = ...;
LLVM_DEBUG({
  llvm::dbgs() << "Types: ";
  llvm::interleave_comma(llvm::dbgs(), types);
  llvm::dbgs() << "\n";
  llvm::dbgs() << "Values: [";
  llvm::interleave_comma(llvm::dbgs(), values);
  llvm::dbgs() << "]\n";
}):
```

After:
```c++
ArrayRef<Type> types = ...;
ArrayRef<Values> values = ...;
LLVM_DEBUG(llvm::dbgs() << "Types: " << interleaved(types) << "\n");
LLVM_DEBUG(llvm::dbgs() << "Values: " << interleaved_array(values) << "\n");
```

The separator and the prefix/suffix strings are customizable.

2 files changed, 72 insertions, 1 deletions

diff --git a/llvm/unittests/Support/CMakeLists.txt b/llvm/unittests/Support/CMakeLists.txt
index 6c4e7cb..4a12a92 100644
--- a/llvm/unittests/Support/CMakeLists.txt
+++ b/llvm/unittests/Support/CMakeLists.txt
@@ -49,6 +49,7 @@ add_llvm_unittest(SupportTests
   HashBuilderTest.cpp
   IndexedAccessorTest.cpp
   InstructionCostTest.cpp
+  InterleavedRangeTest.cpp
   JSONTest.cpp
   KnownBitsTest.cpp
   LEB128Test.cpp
@@ -61,7 +62,7 @@ add_llvm_unittest(SupportTests
   MemoryBufferRefTest.cpp
   MemoryBufferTest.cpp
   MemoryTest.cpp
-  MustacheTest.cpp      
+  MustacheTest.cpp
   ModRefTest.cpp
   NativeFormatTests.cpp
   OptimizedStructLayoutTest.cpp
diff --git a/llvm/unittests/Support/InterleavedRangeTest.cpp b/llvm/unittests/Support/InterleavedRangeTest.cpp
new file mode 100644
index 0000000..8640b81
--- /dev/null
+++ b/llvm/unittests/Support/InterleavedRangeTest.cpp
@@ -0,0 +1,70 @@
+//===- InterleavedRangeTest.cpp - Unit tests for interleaved format -------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/InterleavedRange.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/raw_ostream.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+TEST(InterleavedRangeTest, VectorInt) {
+  SmallVector<int> V = {0, 1, 2, 3};
+
+  // First, make sure that the raw print API works as expected.
+  std::string Buff;
+  raw_string_ostream OS(Buff);
+  OS << interleaved(V);
+  EXPECT_EQ("0, 1, 2, 3", Buff);
+  Buff.clear();
+  OS << interleaved_array(V);
+  EXPECT_EQ("[0, 1, 2, 3]", Buff);
+
+  // In the rest of the tests, use `.str()` for convenience.
+  EXPECT_EQ("0, 1, 2, 3", interleaved(V).str());
+  EXPECT_EQ("{{0,1,2,3}}", interleaved(V, ",", "{{", "}}").str());
+  EXPECT_EQ("[0, 1, 2, 3]", interleaved_array(V).str());
+  EXPECT_EQ("[0;1;2;3]", interleaved_array(V, ";").str());
+  EXPECT_EQ("0;1;2;3", interleaved(V, ";").str());
+}
+
+TEST(InterleavedRangeTest, VectorIntEmpty) {
+  SmallVector<int> V = {};
+  EXPECT_EQ("", interleaved(V).str());
+  EXPECT_EQ("{{}}", interleaved(V, ",", "{{", "}}").str());
+  EXPECT_EQ("[]", interleaved_array(V).str());
+  EXPECT_EQ("", interleaved(V, ";").str());
+}
+
+TEST(InterleavedRangeTest, VectorIntOneElem) {
+  SmallVector<int> V = {42};
+  EXPECT_EQ("42", interleaved(V).str());
+  EXPECT_EQ("{{42}}", interleaved(V, ",", "{{", "}}").str());
+  EXPECT_EQ("[42]", interleaved_array(V).str());
+  EXPECT_EQ("42", interleaved(V, ";").str());
+}
+
+struct CustomPrint {
+  int N;
+  friend raw_ostream &operator<<(raw_ostream &OS, const CustomPrint &CP) {
+    OS << "$$" << CP.N << "##";
+    return OS;
+  }
+};
+
+TEST(InterleavedRangeTest, CustomPrint) {
+  CustomPrint V[] = {{3}, {4}, {5}};
+  EXPECT_EQ("$$3##, $$4##, $$5##", interleaved(V).str());
+  EXPECT_EQ("{{$$3##;$$4##;$$5##}}", interleaved(V, ";", "{{", "}}").str());
+  EXPECT_EQ("[$$3##, $$4##, $$5##]", interleaved_array(V).str());
+}
+
+} // namespace