[PATCH] Change the behavior of predicate check failure on cbranchcc4 operand0 in prepare_cmp_insn

[HAO CHEN GUI via Gcc-patches]

Hi,
  I want to enable "have_cbranchcc4" on rs6000. But not all combinations of
comparison codes and sub CC modes are benefited to generate cbranchcc4 insns
on rs6000. There is an predicate for operand0 of cbranchcc4 to bypass
some combinations. It gets assertion failure in prepare_cmp_insn. I think
we shouldn't suppose that all comparison codes and sub CC modes are supported
and throw an assertion failure in prepare_cmp_insn. It might check the
predicate and go to fail if the predicate can't be satisfied. This patch
changes the behavior of those codes.

  Bootstrapped and tested on powerpc64-linux BE/LE and x86 with no regressions.
Is this okay for trunk? Any recommendations? Thanks a lot.


ChangeLog
2022-11-23  Haochen Gui <guih...@linux.ibm.com>

gcc/
        * optabs.cc (prepare_cmp_insn): Go to fail other than assert it when
        predicate check of "cbranchcc4" operand[0] fails.

patch.diff
diff --git a/gcc/optabs.cc b/gcc/optabs.cc
index 165f8d1fa22..3ec8f6b17ba 100644
--- a/gcc/optabs.cc
+++ b/gcc/optabs.cc
@@ -4484,8 +4484,9 @@ 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));
+      gcc_assert (icode != CODE_FOR_nothing);
+      if (!insn_operand_matches (icode, 0, test))
+       goto fail;
       *ptest = test;
       return;
     }