[gcc r14-6399] RISC-V: Fix ICE in extract_single_source

[Lehua Ding]

https://gcc.gnu.org/g:330bb06485b18bae3effe83b45b97dbdcd543367

commit r14-6399-g330bb06485b18bae3effe83b45b97dbdcd543367
Author: Juzhe-Zhong <juzhe.zhong@rivai.ai>
Date:   Mon Dec 11 14:43:34 2023 +0800

    RISC-V: Fix ICE in extract_single_source
    
    This patch fixes the following ICE in VSETVL PASS:
    bug.c:39:1: internal compiler error: Segmentation fault
       39 | }
          | ^
    0x1ad5a08 crash_signal
            ../../../../gcc/gcc/toplev.cc:316
    0x7f7f55feb90f ???
            ./signal/../sysdeps/unix/sysv/linux/x86_64/libc_sigaction.c:0
    0x218d7c7 extract_single_source
            ../../../../gcc/gcc/config/riscv/riscv-vsetvl.cc:583
    0x218d95d extract_single_source
            ../../../../gcc/gcc/config/riscv/riscv-vsetvl.cc:604
    0x218fbc5 pre_vsetvl::compute_lcm_local_properties()
            ../../../../gcc/gcc/config/riscv/riscv-vsetvl.cc:2703
    0x2190ef4 pre_vsetvl::earliest_fuse_vsetvl_info()
            ../../../../gcc/gcc/config/riscv/riscv-vsetvl.cc:2890
    0x2193e62 pass_vsetvl::lazy_vsetvl()
            ../../../../gcc/gcc/config/riscv/riscv-vsetvl.cc:3537
    0x219406a pass_vsetvl::execute(function*)
            ../../../../gcc/gcc/config/riscv/riscv-vsetvl.cc:3584
    
    The rootcause we have a case that the def info can not be traced:
    
    (insn 208 327 333 27 (use (reg/i:DI 10 a0)) "bug.c":36:1 -1
         (nil))
    
    It's obvious, we conservatively disable any optimization in this situation if
    AVL def_info can not be tracded.
    
    Committed as it is obvious.
    
    gcc/ChangeLog:
    
            * config/riscv/riscv-vsetvl.cc (extract_single_source): Fix ICE.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/riscv/rvv/vsetvl/avl_use_bug-1.c: New test.

Diff:
---
 gcc/config/riscv/riscv-vsetvl.cc                   |  2 ++
 .../gcc.target/riscv/rvv/vsetvl/avl_use_bug-1.c    | 39 ++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/gcc/config/riscv/riscv-vsetvl.cc b/gcc/config/riscv/riscv-vsetvl.cc
index 90477f331d7..ed5a2b58ab0 100644
--- a/gcc/config/riscv/riscv-vsetvl.cc
+++ b/gcc/config/riscv/riscv-vsetvl.cc
@@ -579,6 +579,8 @@ extract_single_source (set_info *set)
   if (!set->insn ()->is_phi ())
     return nullptr;
   hash_set<set_info *> sets = get_all_sets (set, true, false, true);
+  if (sets.is_empty ())
+    return nullptr;
 
   insn_info *first_insn = (*sets.begin ())->insn ();
   if (first_insn->is_artificial ())
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/avl_use_bug-1.c b/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/avl_use_bug-1.c
new file mode 100644
index 00000000000..330221c2d7b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/vsetvl/avl_use_bug-1.c
@@ -0,0 +1,39 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gcv_zvl256b -mabi=lp64 --param=riscv-autovec-lmul=m8 --param=riscv-autovec-preference=fixed-vlmax -O2" } */
+
+struct a_struct
+{
+  unsigned char a_character;
+};
+
+struct a_struct an_array[5];
+struct a_struct *a_ptr;
+int yabba = 1;
+
+int
+f (a, b)
+     unsigned char a;
+     unsigned long b;
+{
+  long i, j, p, q, r, s;
+
+  if (b != (unsigned long) 0)
+    {
+      if (yabba)
+	return -1;
+      s = 4000000 / b;
+      for (i = 0; i < 11; i++)
+	{
+	  for (j = 0; j < 256; j++)
+	    {
+	      if (((p - s < 0) ? -s : 0) < (( q - s < 0) ? -s : q))
+		r = i;
+	    }
+	}
+    }
+
+  if (yabba)
+    return 0;
+  a_ptr = &an_array[a];
+  a_ptr->a_character = (unsigned char) r;
+}