[gcc r13-4627] optabs: make prepare_cmp_insn goto fail when cbranchcc4 checks unsatisfied

[HaoChen Gui <guihaoc@gcc.gnu.org>]

https://gcc.gnu.org/g:99cce60d0b8f3c3a77be8e1bb716f3e2fee37d46

commit r13-4627-g99cce60d0b8f3c3a77be8e1bb716f3e2fee37d46
Author: Haochen Gui <guihaoc@gcc.gnu.org>
Date:   Thu Dec 8 13:22:29 2022 +0800

    optabs: make prepare_cmp_insn goto fail when cbranchcc4 checks unsatisfied
    
    prepare_cmp_insn is a help function to generate comparison rtx.
    It should not assume that cbranchcc4 exists and all sub-CC modes
    are supported on a target.  When the check fails, it could go to
    fail and return a NULL rtx as its callers check the return value
    for CCmode.
    
    The test case (gcc.target/powerpc/cbranchcc4-1.c) which covers
    failure path will be committed with an rs6000 specific patch.
    
    2022-12-05  Haochen Gui <guihaoc@linux.ibm.com>
    
    gcc/
            * optabs.cc (prepare_cmp_insn): Return a NULL rtx other than
            assertion failure when targets don't have cbranch optab or
            predicate check fails.

Diff:
---
 gcc/optabs.cc | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/gcc/optabs.cc b/gcc/optabs.cc
index 262a37f9b3f..2ffd455202d 100644
--- a/gcc/optabs.cc
+++ b/gcc/optabs.cc
@@ -4491,10 +4491,14 @@ prepare_cmp_insn (rtx x, rtx y, enum rtx_code comparison, rtx size,
     {
       enum insn_code icode = optab_handler (cbranch_optab, CCmode);
       test = gen_rtx_fmt_ee (comparison, VOIDmode, x, y);
-      gcc_assert (icode != CODE_FOR_nothing
-                  && insn_operand_matches (icode, 0, test));
-      *ptest = test;
-      return;
+      if (icode != CODE_FOR_nothing
+	  && insn_operand_matches (icode, 0, test))
+	{
+	  *ptest = test;
+	  return;
+	}
+      else
+	goto fail;
     }
 
   test = gen_rtx_fmt_ee (comparison, VOIDmode, x, y);