Add expr_callee_abi

[Richard Sandiford]

This turned out to be useful for the SVE PCS support, and is a natural
tree-level analogue of insn_callee_abi.

Tested on aarch64-linux-gnu and x86_64-linux-gnu.  OK to install?

Richard


2019-10-11  Richard Sandiford  <richard.sandif...@arm.com>

gcc/
        * function-abi.h (expr_callee_abi): Declare.
        * function-abi.cc (expr_callee_abi): New function.

Index: gcc/function-abi.h
===================================================================
--- gcc/function-abi.h  2019-09-30 17:39:33.514597856 +0100
+++ gcc/function-abi.h  2019-10-11 15:38:54.141605718 +0100
@@ -315,5 +315,6 @@ call_clobbered_in_region_p (unsigned int
 extern const predefined_function_abi &fntype_abi (const_tree);
 extern function_abi fndecl_abi (const_tree);
 extern function_abi insn_callee_abi (const rtx_insn *);
+extern function_abi expr_callee_abi (const_tree);
 
 #endif
Index: gcc/function-abi.cc
===================================================================
--- gcc/function-abi.cc 2019-09-30 17:39:33.514597856 +0100
+++ gcc/function-abi.cc 2019-10-11 15:38:54.141605718 +0100
@@ -229,3 +229,32 @@ insn_callee_abi (const rtx_insn *insn)
 
   return default_function_abi;
 }
+
+/* Return the ABI of the function called by CALL_EXPR EXP.  Return the
+   default ABI for erroneous calls.  */
+
+function_abi
+expr_callee_abi (const_tree exp)
+{
+  gcc_assert (TREE_CODE (exp) == CALL_EXPR);
+
+  if (tree fndecl = get_callee_fndecl (exp))
+    return fndecl_abi (fndecl);
+
+  tree callee = CALL_EXPR_FN (exp);
+  if (callee == error_mark_node)
+    return default_function_abi;
+
+  tree type = TREE_TYPE (callee);
+  if (type == error_mark_node)
+    return default_function_abi;
+
+  if (POINTER_TYPE_P (type))
+    {
+      type = TREE_TYPE (type);
+      if (type == error_mark_node)
+       return default_function_abi;
+    }
+
+  return fntype_abi (type);
+}