RISC-V:Bugfix for vlmul_ext and vlmul_trunc with NULL return value[pr117286]

This patch fixes following ICE:

test.c: In function 'func':
test.c:37:24: internal compiler error: Segmentation fault
   37 |     vfloat16mf2_t vc = __riscv_vlmul_trunc_v_f16m1_f16mf2(vb);
      |                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The root cause is that vlmul_trunc has a null return value.
gimple_call <__riscv_vlmul_trunc_v_f16m1_f16mf2, NULL, vb_13>
                                                 ^^^

Passed the rv64gcv_zvfh regression test.

Singed-off-by: Li Xu <xuli1@eswincomputing.com>

	PR target/117286

gcc/ChangeLog:

	* config/riscv/riscv-vector-builtins-bases.cc: Do not expand NULL return.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/base/pr117286.c: New test.

1 files changed, 4 insertions, 0 deletions

diff --git a/gcc/config/riscv/riscv-vector-builtins-bases.cc b/gcc/config/riscv/riscv-vector-builtins-bases.cc
index fcc1bf9..b8c337f 100644
--- a/gcc/config/riscv/riscv-vector-builtins-bases.cc
+++ b/gcc/config/riscv/riscv-vector-builtins-bases.cc
@@ -1753,6 +1753,8 @@ public:
 
   rtx expand (function_expander &e) const override
   {
+    if (!e.target)
+      return NULL_RTX;
     tree arg = CALL_EXPR_ARG (e.exp, 0);
     rtx src = expand_normal (arg);
     emit_move_insn (gen_lowpart (e.vector_mode (), e.target), src);
@@ -1767,6 +1769,8 @@ public:
 
   rtx expand (function_expander &e) const override
   {
+    if (!e.target)
+      return NULL_RTX;
     rtx src = expand_normal (CALL_EXPR_ARG (e.exp, 0));
     emit_move_insn (e.target, gen_lowpart (GET_MODE (e.target), src));
     return e.target;