[gcc r14-8354] aarch64: Avoid registering duplicate C++ overloads [PR112989]

[Richard Sandiford <rsandifo@gcc.gnu.org>]

https://gcc.gnu.org/g:659a5a908edd84894c2aa7f6f89468217d6894ca

commit r14-8354-g659a5a908edd84894c2aa7f6f89468217d6894ca
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Tue Jan 23 11:10:41 2024 +0000

    aarch64: Avoid registering duplicate C++ overloads [PR112989]
    
    In the original fix for this PR, I'd made sure that
    including <arm_sme.h> didn't reach the final return in
    simulate_builtin_function_decl (which would indicate duplicate
    function definitions).  But it seems I forgot to do the same
    thing for C++, which defines all of its overloads directly.
    
    This patch fixes a case where we still recorded duplicate
    functions for C++.  Thanks to Iain for reporting the resulting
    GC ICE and for help with reproducing it.
    
    gcc/
            PR target/112989
            * config/aarch64/aarch64-sve-builtins-shapes.cc (build_one): Skip
            MODE_single variants of functions that don't take tuple arguments.

Diff:
---
 gcc/config/aarch64/aarch64-sve-builtins-shapes.cc | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/gcc/config/aarch64/aarch64-sve-builtins-shapes.cc b/gcc/config/aarch64/aarch64-sve-builtins-shapes.cc
index 2692b086ac5..f190770250f 100644
--- a/gcc/config/aarch64/aarch64-sve-builtins-shapes.cc
+++ b/gcc/config/aarch64/aarch64-sve-builtins-shapes.cc
@@ -338,6 +338,14 @@ build_one (function_builder &b, const char *signature,
 	   unsigned int ti, unsigned int gi, unsigned int pi,
 	   bool force_direct_overloads)
 {
+  /* For simplicity, function definitions are allowed to use the group
+     suffix lists vg2 and vg4 for shapes that have _single forms,
+     even though the _single form applies only to vgNx2 and vgNx4,
+     not to vgNx1.  */
+  if (mode_suffix_id == MODE_single
+      && group_suffixes[group.groups[gi]].vectors_per_tuple == 1)
+    return;
+
   /* Byte forms of svdupq take 16 arguments.  */
   auto_vec<tree, 16> argument_types;
   function_instance instance (group.base_name, *group.base, *group.shape,