[gcc r11-10319] Fix register count when not splitting Complex IEEE 128-bit args.

[Pat Haugen <pthaugen@gcc.gnu.org>]

https://gcc.gnu.org/g:e7f0d923dc29965ff92f27245ea63c5726edcacd

commit r11-10319-ge7f0d923dc29965ff92f27245ea63c5726edcacd
Author: Pat Haugen <pthaugen@linux.ibm.com>
Date:   Mon Oct 17 15:11:42 2022 -0500

    Fix register count when not splitting Complex IEEE 128-bit args.
    
    For ABI_V4, we do not split complex args. This created a problem because
    even though an arg would be passed in two VSX regs, we were only advancing the
    function arg counter by one VSX register. Fixed with this patch.
    
    (backported commit 2ee68beee709e48fce85b8892ff9985acc6a91a8)
    
    gcc/
            PR target/99685
            * config/rs6000/rs6000-call.c (rs6000_function_arg_advance_1): Bump
            register count when not splitting IEEE 128-bit Complex.

Diff:
---
 gcc/config/rs6000/rs6000-call.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/gcc/config/rs6000/rs6000-call.c b/gcc/config/rs6000/rs6000-call.c
index e58b149d022..1be4797e834 100644
--- a/gcc/config/rs6000/rs6000-call.c
+++ b/gcc/config/rs6000/rs6000-call.c
@@ -7190,6 +7190,12 @@ rs6000_function_arg_advance_1 (CUMULATIVE_ARGS *cum, machine_mode mode,
 	{
 	  cum->vregno += n_elts;
 
+	  /* If we are not splitting Complex IEEE128 args then account for the
+	     fact that they are passed in 2 VSX regs. */
+	  if (!targetm.calls.split_complex_arg && type
+	      && TREE_CODE (type) == COMPLEX_TYPE && elt_mode == KCmode)
+	    cum->vregno++;
+
 	  if (!TARGET_ALTIVEC)
 	    error ("cannot pass argument in vector register because"
 		   " altivec instructions are disabled, use %qs"