[LangRef] Require elementtype attribute for gc.statepoint intrinsic

The gc.statepoint intrinsic currently determines the target function
type based on the pointer element type of the argument. In order to
support opaque pointers, require that the argument is annotated with
an elementtype attribute.

Here's an example of the change:

    ; Before:
      %safepoint_token = tail call token (i64, i32, i1 ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_i1f(i64 0, i32 0, i1 ()* @return_i1, i32 0, i32 0, i32 0, i32 0)

    ; After:
      %safepoint_token = tail call token (i64, i32, i1 ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_i1f(i64 0, i32 0, i1 ()* elementtype(i1 ()) @return_i1, i32 0, i32 0, i32 0, i32 0)

    ; After with opaque pointers:
      %safepoint_token = tail call token (i64, i32, i1 ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0(i64 0, i32 0, ptr elementtype(i1 ()) @return_i1, i32 0, i32 0, i32 0, i32 0)

Differential Revision: https://reviews.llvm.org/D117890

diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 920834b..41e4714 100644 (file)
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -12251,7 +12251,7 @@ Syntax:
 
       declare token
         @llvm.experimental.gc.statepoint(i64 <id>, i32 <num patch bytes>,
-                       func_type <target>,
+                       func_type* elementtype(func_type) <target>,
                        i64 <#call args>, i64 <flags>,
                        ... (call parameters),
                        i64 0, i64 0)
@@ -12287,11 +12287,12 @@ statepoint still represents a call or invoke to 'target', and the nop
 sequence after patching is expected to represent an operation
 equivalent to a call or invoke to 'target'.
 
-The 'target' operand is the function actually being called.  The
-target can be specified as either a symbolic LLVM function, or as an
-arbitrary Value of appropriate function type.  Note that the function
-type must match the signature of the callee and the types of the 'call
-parameters' arguments.
+The 'target' operand is the function actually being called. The operand
+must have an :ref:`elementtype <attr_elementtype>` attribute specifying
+the function type of the target. The target can be specified as either
+a symbolic LLVM function, or as an arbitrary Value of pointer type. Note
+that the function type must match the signature of the callee and the
+types of the 'call parameters' arguments.
 
 The '#call args' operand is the number of arguments to the actual
 call.  It must exactly match the number of arguments passed in the