[Bug target/120839] [16 Regression] Incorrect alignment for arguments on stack

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120839

--- Comment #11 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #10)
> In fact the AMD64 ABI says "If the class is MEMORY ,pass trhe argument on
> the stack at an address respecting the arguments alignemnt (which might be
> more than its natural alignment).  So
> 
> diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
> index acedc73b825..b43d50b6bc3 100644
> --- a/gcc/config/i386/i386.cc
> +++ b/gcc/config/i386/i386.cc
> @@ -3803,9 +3803,6 @@ ix86_function_arg_boundary (machine_mode mode,
> const_tree type)
>    unsigned int align;
>    if (type)
>      {
> -      /* Since the main variant type is used for call, we convert it to
> -        the main variant type.  */
> -      type = TYPE_MAIN_VARIANT (type);
>        align = TYPE_ALIGN (type);
>        if (TYPE_EMPTY_P (type))
>         return PARM_BOUNDARY;

More defensive

diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index acedc73b825..c9f58b1eace 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -3803,10 +3803,10 @@ ix86_function_arg_boundary (machine_mode mode,
const_tree type)
   unsigned int align;
   if (type)
     {
+      align = TYPE_ALIGN (type);
       /* Since the main variant type is used for call, we convert it to
         the main variant type.  */
       type = TYPE_MAIN_VARIANT (type);
-      align = TYPE_ALIGN (type);
       if (TYPE_EMPTY_P (type))
        return PARM_BOUNDARY;
     }

causes

+FAIL: gcc.dg/torture/pr35771-1.c   -O0  execution test
+FAIL: gcc.dg/torture/pr35771-1.c   -O1  execution test
+FAIL: gcc.dg/torture/pr35771-2.c   -O0  execution test
+FAIL: gcc.dg/torture/pr35771-2.c   -O1  execution test
+FAIL: gcc.dg/torture/pr35771-3.c   -O0  execution test
+FAIL: gcc.dg/torture/pr35771-3.c   -O1  execution test
+FAIL: gcc.target/i386/pr35767-3.c execution test

I did not check struct-compat against an alt GCC.