[LangRef] Clarify codegen expectations for intrinsics with fp/integer-only overloads.

This change is a result of discussions on list: "GlobalISel: Ambiguous intrinsic semantics problem"

Differential Revision: https://reviews.llvm.org/D59657

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@364610 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/docs/LangRef.rst b/docs/LangRef.rst
index 14d7d57f19bb1b83ec63eac456b2ae4bf3f9516f..e7dd40af168d49946fc7847334f19c2cef05fb6a 100644 (file)
--- a/docs/LangRef.rst
+++ b/docs/LangRef.rst
@@ -10480,6 +10480,16 @@ overloaded, and only one type suffix is required. Because the argument's
 type is matched against the return type, it does not require its own
 name suffix.
 
+For target developers who are defining intrinsics for back-end code
+generation, any intrinsic overloads based solely the distinction between
+integer or floating point types should not be relied upon for correct
+code generation. In such cases, the recommended approach for target
+maintainers when defining intrinsics is to create separate integer and
+FP intrinsics rather than rely on overloading. For example, if different
+codegen is required for ``llvm.target.foo(<4 x i32>)`` and
+``llvm.target.foo(<4 x float>)`` then these should be split into
+different intrinsics.
+
 To learn how to add an intrinsic function, please see the `Extending
 LLVM Guide <ExtendingLLVM.html>`_.