[PATCH] symtab-thunks: Use aggregate_value_p even on is_gimple_reg_type returns [PR112941]

[Jakub Jelinek]

Hi!

Large/huge _BitInt types are returned in memory and the bitint lowering
pass right now relies on that.
The gimplification etc. use aggregate_value_p to see if it should be
returned in memory or not and use
  <retval> = _123;
  return <retval>;
rather than
  return _123;
But expand_thunk used e.g. by IPA-ICF was performing an optimization,
assuming is_gimple_reg_type is always passed in registers and not calling
aggregate_value_p in that case.  The following patch changes it to match
what the gimplification etc. are doing.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2023-12-22  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/112941
        * symtab-thunks.cc (expand_thunk): Check aggregate_value_p regardless
        of whether is_gimple_reg_type (restype) or not.

        * gcc.dg/bitint-60.c: New test.

--- gcc/symtab-thunks.cc.jj     2023-08-24 15:37:28.698418172 +0200
+++ gcc/symtab-thunks.cc        2023-12-21 16:42:41.406127267 +0100
@@ -479,21 +479,15 @@ expand_thunk (cgraph_node *node, bool ou
                                 resdecl,
                                 build_int_cst (TREE_TYPE (resdecl), 0));
            }
-         else if (!is_gimple_reg_type (restype))
+         else if (aggregate_value_p (resdecl, TREE_TYPE (thunk_fndecl)))
            {
-             if (aggregate_value_p (resdecl, TREE_TYPE (thunk_fndecl)))
-               {
-                 restmp = resdecl;
+             restmp = resdecl;
 
-                 if (VAR_P (restmp))
-                   {
-                     add_local_decl (cfun, restmp);
-                     BLOCK_VARS (DECL_INITIAL (current_function_decl))
-                       = restmp;
-                   }
+             if (VAR_P (restmp))
+               {
+                 add_local_decl (cfun, restmp);
+                 BLOCK_VARS (DECL_INITIAL (current_function_decl)) = restmp;
                }
-             else
-               restmp = create_tmp_var (restype, "retval");
            }
          else
            restmp = create_tmp_reg (restype, "retval");
--- gcc/testsuite/gcc.dg/bitint-60.c.jj 2023-12-21 16:49:41.289298560 +0100
+++ gcc/testsuite/gcc.dg/bitint-60.c    2023-12-21 16:49:09.061746003 +0100
@@ -0,0 +1,20 @@
+/* PR tree-optimization/112941 */
+/* { dg-do compile { target bitint575 } } */
+/* { dg-options "-O2 -std=c23" } */
+
+unsigned _BitInt(495) f1 (signed _BitInt(381) x) { unsigned _BitInt(539) y = 
x; return y; }
+unsigned _BitInt(495) f2 (unsigned _BitInt(381) x) { unsigned _BitInt(539) y = 
x; return y; }
+unsigned _BitInt(495) f3 (signed _BitInt(381) x) { _BitInt(539) y = x; return 
y; }
+unsigned _BitInt(495) f4 (unsigned _BitInt(381) x) { _BitInt(539) y = x; 
return y; }
+_BitInt(495) f5 (signed _BitInt(381) x) { unsigned _BitInt(539) y = x; return 
y; }
+_BitInt(495) f6 (unsigned _BitInt(381) x) { unsigned _BitInt(539) y = x; 
return y; }
+_BitInt(495) f7 (signed _BitInt(381) x) { _BitInt(539) y = x; return y; }
+_BitInt(495) f8 (unsigned _BitInt(381) x) { _BitInt(539) y = x; return y; }
+unsigned _BitInt(495) f9 (signed _BitInt(381) x) { return (unsigned 
_BitInt(539)) x; }
+unsigned _BitInt(495) f10 (unsigned _BitInt(381) x) { return (unsigned 
_BitInt(539)) x; }
+unsigned _BitInt(495) f11 (signed _BitInt(381) x) { return (_BitInt(539)) x; }
+unsigned _BitInt(495) f12 (unsigned _BitInt(381) x) { return (_BitInt(539)) x; 
}
+_BitInt(495) f13 (signed _BitInt(381) x) { return (unsigned _BitInt(539)) x; }
+_BitInt(495) f14 (unsigned _BitInt(381) x) { return (unsigned _BitInt(539)) x; 
}
+_BitInt(495) f15 (signed _BitInt(381) x) { return (_BitInt(539)) x; }
+_BitInt(495) f16 (unsigned _BitInt(381) x) { return (_BitInt(539)) x; }

        Jakub