[gcc r14-6805] symtab-thunks: Use aggregate_value_p even on is_gimple_reg_type returns [PR112941]

[Jakub Jelinek]

https://gcc.gnu.org/g:0a6aa1927597d821a85bc3d1fd7682256c25b548

commit r14-6805-g0a6aa1927597d821a85bc3d1fd7682256c25b548
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri Dec 22 12:28:54 2023 +0100

    symtab-thunks: Use aggregate_value_p even on is_gimple_reg_type returns [PR112941]
    
    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.
    
    2023-12-22  Jakub Jelinek  <jakub@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.

Diff:
---
 gcc/symtab-thunks.cc             | 18 ++++++------------
 gcc/testsuite/gcc.dg/bitint-60.c | 20 ++++++++++++++++++++
 2 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/gcc/symtab-thunks.cc b/gcc/symtab-thunks.cc
index 23ead0d2138..0e5fc4f90d2 100644
--- a/gcc/symtab-thunks.cc
+++ b/gcc/symtab-thunks.cc
@@ -479,21 +479,15 @@ expand_thunk (cgraph_node *node, bool output_asm_thunks,
 				 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;
+
+	      if (VAR_P (restmp))
 		{
-		  restmp = resdecl;
-
-		  if (VAR_P (restmp))
-		    {
-		      add_local_decl (cfun, restmp);
-		      BLOCK_VARS (DECL_INITIAL (current_function_decl))
-			= 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");
diff --git a/gcc/testsuite/gcc.dg/bitint-60.c b/gcc/testsuite/gcc.dg/bitint-60.c
new file mode 100644
index 00000000000..d1916a03490
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/bitint-60.c
@@ -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; }