[PATCH] D60291: [llvm] Add isa_and_nonnull

[Don Hinton via Phabricator via llvm-commits]

hintonda created this revision.
hintonda added reviewers: lattner, aaron.ballman, greened.
Herald added a project: LLVM.

Add new ``isa_and_nonnull<>`` operator that works just like
the ``isa<>`` operator, except that it allows for a null pointer as an
argument (which it then returns false).

The final name has not yet been determined, but a discussion can be
seen here: http://lists.llvm.org/pipermail/llvm-dev/2019-April/131555.html


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D60291

Files:
  llvm/docs/ProgrammersManual.rst
  llvm/include/llvm/Support/Casting.h
  llvm/unittests/Support/Casting.cpp


Index: llvm/unittests/Support/Casting.cpp
===================================================================
--- llvm/unittests/Support/Casting.cpp
+++ llvm/unittests/Support/Casting.cpp
@@ -118,6 +118,12 @@
   EXPECT_TRUE(isa<foo>(B4));
 }
 
+TEST(CastingTest, isa_and_nonnull) {
+  EXPECT_TRUE(isa_and_nonnull<foo>(B2));
+  EXPECT_TRUE(isa_and_nonnull<foo>(B4));
+  EXPECT_FALSE(isa_and_nonnull<foo>(fub()));
+}
+
 TEST(CastingTest, cast) {
   foo &F1 = cast<foo>(B1);
   EXPECT_NE(&F1, null_foo);
Index: llvm/include/llvm/Support/Casting.h
===================================================================
--- llvm/include/llvm/Support/Casting.h
+++ llvm/include/llvm/Support/Casting.h
@@ -143,6 +143,16 @@
                        typename simplify_type<const Y>::SimpleType>::doit(Val);
 }
 
+// isa_and_nonnull<X> - Functionally identical to isa, except that a null value
+// is accepted.
+//
+template <class X, class Y>
+LLVM_NODISCARD inline bool isa_and_nonnull(const Y &Val) {
+  if (!Val)
+    return false;
+  return isa<X>(Val);
+}
+
 //===----------------------------------------------------------------------===//
 //                          cast<x> Support Templates
 //===----------------------------------------------------------------------===//
Index: llvm/docs/ProgrammersManual.rst
===================================================================
--- llvm/docs/ProgrammersManual.rst
+++ llvm/docs/ProgrammersManual.rst
@@ -164,6 +164,12 @@
   efficient to use the ``InstVisitor`` class to dispatch over the instruction
   type directly.
 
+``isa_and_nonnull<>``:
+  The ``isa_and_nonnull<>`` operator works just like the ``isa<>`` operator,
+  except that it allows for a null pointer as an argument (which it then
+  returns false).  This can sometimes be useful, allowing you to combine several
+  null checks into one.
+
 ``cast_or_null<>``:
   The ``cast_or_null<>`` operator works just like the ``cast<>`` operator,
   except that it allows for a null pointer as an argument (which it then


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