[gcc r13-6495] RISC-V: Fix ICE for avl_single-86/avl_single-88/avl_single-90

[gcc r13-6495] RISC-V: Fix ICE for avl_single-86/avl_single-88/avl_single-90

[Kito Cheng]

https://gcc.gnu.org/g:44c918b50af64d1c0f27067b2671e1a4f744841b

commit r13-6495-g44c918b50af64d1c0f27067b2671e1a4f744841b
Author: Ju-Zhe Zhong <juzhe.zhong@rivai.ai>
Date:   Sun Mar 5 18:24:30 2023 +0800

    RISC-V: Fix ICE for avl_single-86/avl_single-88/avl_single-90
    
    If prop is demand of vsetvl instruction and reaching doesn't demand
    AVL. We don't backward propagate since vsetvl instruction has no
    side effects.
    
    FAIL: gcc.target/riscv/rvv/vsetvl/avl_single-86.c  -Og -g  (internal
    compiler error: Segmentation fault)
    FAIL: gcc.target/riscv/rvv/vsetvl/avl_single-86.c  -Og -g  (test for
    excess errors)
    FAIL: gcc.target/riscv/rvv/vsetvl/avl_single-88.c  -Og -g  (internal
    compiler error: Segmentation fault)
    FAIL: gcc.target/riscv/rvv/vsetvl/avl_single-88.c  -Og -g  (test for
    excess errors)
    FAIL: gcc.target/riscv/rvv/vsetvl/avl_single-90.c  -Og -g  (internal
    compiler error: Segmentation fault)
    FAIL: gcc.target/riscv/rvv/vsetvl/avl_single-90.c  -Og -g  (test for
    excess errors)
    
    gcc/ChangeLog:
    
            * config/riscv/riscv-vsetvl.cc (reg_available_p): Fix bug.
            (pass_vsetvl::backward_demand_fusion): Ditto.

Diff:
---
 gcc/config/riscv/riscv-vsetvl.cc | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/gcc/config/riscv/riscv-vsetvl.cc b/gcc/config/riscv/riscv-vsetvl.cc
index 9e25102a4f2..73f36a70331 100644
--- a/gcc/config/riscv/riscv-vsetvl.cc
+++ b/gcc/config/riscv/riscv-vsetvl.cc
@@ -1528,7 +1528,7 @@ static bool
 reg_available_p (const bb_info *bb, const vector_insn_info &info)
 {
   if (!info.get_avl_source ())
-    return true;
+    return false;
   insn_info *insn = info.get_avl_source ()->insn ();
   if (insn->bb () == bb)
     return before_p (insn, info.get_insn ());
@@ -3040,6 +3040,12 @@ pass_vsetvl::backward_demand_fusion (void)
 	    continue;
 	  if (e->src->index == ENTRY_BLOCK_PTR_FOR_FN (cfun)->index)
 	    continue;
+	  /* If prop is demand of vsetvl instruction and reaching doesn't demand
+	     AVL. We don't backward propagate since vsetvl instruction has no
+	     side effects.  */
+	  if (vsetvl_insn_p (prop.get_insn ()->rtl ())
+	      && propagate_avl_across_demands_p (prop, block_info.reaching_out))
+	    continue;
 
 	  if (block_info.reaching_out.unknown_p ())
 	    continue;