RISC-V: Insert vsetivli zero, 0 for vmv.x.s/vfmv.f.s instructions sat…

…isfying REG_P(operand[1]) in -O0.

This issue happens is because the operand1 of scalar move can be
REG_P (operand[1]) in the O0 case, which causes the VSETVL PASS to
not insert the vsetvl instruction correctly, and the compiler crashes.

Consider this following case:
int16_t foo1 (void *base, size_t vl)
{
    int16_t maxVal = __riscv_vmv_x_s_i16m1_i16 (__riscv_vle16_v_i16m1 (base, vl));
    return maxVal;
}

Before this patch:
bug.c:15:1: internal compiler error: Segmentation fault
   15 | }
      | ^
0x145d723 crash_signal
	../.././riscv-gcc/gcc/toplev.cc:314
0x22929dd const_csr_operand(rtx_def*, machine_mode)
	../.././riscv-gcc/gcc/config/riscv/predicates.md:44
0x2292a21 csr_operand(rtx_def*, machine_mode)
	../.././riscv-gcc/gcc/config/riscv/predicates.md:46
0x23dfbb0 recog_356
	../.././riscv-gcc/gcc/config/riscv/iterators.md:72
0x23efecd recog(rtx_def*, rtx_insn*, int*)
	../.././riscv-gcc/gcc/config/riscv/iterators.md:89
0xdddc15 recog_memoized(rtx_insn*)
	../.././riscv-gcc/gcc/recog.h:273

After this patch:
	vsetivli	zero,0,e16,m1,ta,ma
	vmv.x.s	a5,v1

gcc/ChangeLog:

	* config/riscv/riscv-vsetvl.cc (gen_vsetvl_pat): For vfmv.f.s/vmv.x.s
	intruction replace null avl with (const_int 0).

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/base/scalar_move-10.c: New test.
	* gcc.target/riscv/rvv/base/scalar_move-11.c: New test.

gcc/config/riscv/riscv-vsetvl.cc

@@ -618,6 +618,11 @@ static rtx
 gen_vsetvl_pat (enum vsetvl_type insn_type, const vl_vtype_info &info, rtx vl)
 {
   rtx avl = info.get_avl ();
+  /* if optimization == 0 and the instruction is vmv.x.s/vfmv.f.s,
+     set the value of avl to (const_int 0) so that VSETVL PASS will
+     insert vsetvl correctly.*/
+  if (info.has_avl_no_reg ())
+    avl = GEN_INT (0);
   rtx sew = gen_int_mode (info.get_sew (), Pmode);
   rtx vlmul = gen_int_mode (info.get_vlmul (), Pmode);
   rtx ta = gen_int_mode (info.get_ta (), Pmode);

gcc/testsuite/gcc.target/riscv/rvv/base/scalar_move-10.c

@@ -0,0 +1,31 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d -O0" } */
+/* { dg-final { check-function-bodies "**" "" } } */
+
+#include "riscv_vector.h"
+
+/*
+** foo1:
+** ...
+** vsetivli\tzero,0,e16,m1,t[au],m[au]
+** vmv.x.s\t[a-x0-9]+,v[0-9]+
+** ...
+*/
+int16_t foo1 (void *base, size_t vl)
+{
+    int16_t maxVal = __riscv_vmv_x_s_i16m1_i16 (__riscv_vle16_v_i16m1 (base, vl));
+    return maxVal;
+}
+
+/*
+** foo2:
+** ...
+** vsetivli\tzero,0,e32,m1,t[au],m[au]
+** vfmv.f.s\tf[a-x0-9]+,v[0-9]+
+** ...
+*/
+float foo2 (void *base, size_t vl)
+{
+    float maxVal = __riscv_vfmv_f_s_f32m1_f32 (__riscv_vle32_v_f32m1 (base, vl));
+    return maxVal;
+}

gcc/testsuite/gcc.target/riscv/rvv/base/scalar_move-11.c

@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv32gcv -mabi=ilp32d -O0" } */
+/* { dg-final { check-function-bodies "**" "" } } */
+
+#include "riscv_vector.h"
+
+/*
+** foo:
+** ...
+** vsetivli\tzero,0,e64,m4,t[au],m[au]
+** vmv.x.s\t[a-x0-9]+,v[0-9]+
+** vsetivli\tzero,0,e64,m4,t[au],m[au]
+** vmv.x.s\t[a-x0-9]+,v[0-9]+
+** ...
+*/
+int16_t foo (void *base, size_t vl)
+{
+    int16_t maxVal = __riscv_vmv_x_s_i64m4_i64 (__riscv_vle64_v_i64m4 (base, vl));
+    return maxVal;
+}