[PATCH] RISC-V: Fix SUBREG move of VLS mode[PR111486]

[Juzhe-Zhong]

This patch fixes this bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111486

Before this patch, we can only handle (subreg:DI (reg:V8QI))

The PR ICE:

during RTL pass: reload
testcase.c: In function 'foo':
testcase.c:8:1: internal compiler error: in require, at machmode.h:313
    8 | }
      | ^
0xa40cd2 opt_mode<machine_mode>::require() const
        /repo/gcc-trunk/gcc/machmode.h:313
0xa47091 opt_mode<machine_mode>::require() const
        /repo/gcc-trunk/gcc/config/riscv/riscv.cc:2546
0xa47091 riscv_legitimize_move(machine_mode, rtx_def*, rtx_def*)
        /repo/gcc-trunk/gcc/config/riscv/riscv.cc:2543
0x1f1df10 gen_movdi(rtx_def*, rtx_def*)
        /repo/gcc-trunk/gcc/config/riscv/riscv.md:2024
0x10f1423 rtx_insn* insn_gen_fn::operator()<rtx_def*, rtx_def*>(rtx_def*, 
rtx_def*) const
        /repo/gcc-trunk/gcc/recog.h:411
0x10f1423 emit_move_insn_1(rtx_def*, rtx_def*)
        /repo/gcc-trunk/gcc/expr.cc:4164
0x10f183d emit_move_insn(rtx_def*, rtx_def*)
        /repo/gcc-trunk/gcc/expr.cc:4334
0x13070ec lra_emit_move(rtx_def*, rtx_def*)
        /repo/gcc-trunk/gcc/lra.cc:509
0x132295b curr_insn_transform
        /repo/gcc-trunk/gcc/lra-constraints.cc:4748
0x1324335 lra_constraints(bool)
        /repo/gcc-trunk/gcc/lra-constraints.cc:5488
0x130a3d4 lra(_IO_FILE*)
        /repo/gcc-trunk/gcc/lra.cc:2419
0x12bb629 do_reload
        /repo/gcc-trunk/gcc/ira.cc:5970
0x12bb629 execute
        /repo/gcc-trunk/gcc/ira.cc:6156

Because of (subreg:DI (reg:V2QI))

        PR target/111486

gcc/ChangeLog:

        * config/riscv/riscv.cc (riscv_legitimize_move): Fix bug.

gcc/testsuite/ChangeLog:

        * gcc.target/riscv/rvv/autovec/pr111486.c: New test.

---
 gcc/config/riscv/riscv.cc                             |  3 ++-
 gcc/testsuite/gcc.target/riscv/rvv/autovec/pr111486.c | 11 +++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/autovec/pr111486.c

diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 29d439b4282..6158953098d 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -2525,7 +2525,8 @@ riscv_legitimize_move (machine_mode mode, rtx dest, rtx 
src)
       machine_mode vmode = GET_MODE (SUBREG_REG (src));
       unsigned int mode_size = GET_MODE_SIZE (mode).to_constant ();
       unsigned int vmode_size = GET_MODE_SIZE (vmode).to_constant ();
-      unsigned int nunits = vmode_size / mode_size;
+      /* We should be able to handle both partial and paradoxical subreg.  */
+      unsigned int nunits = vmode_size > mode_size ? vmode_size / mode_size : 
1;
       scalar_mode smode = as_a<scalar_mode> (mode);
       unsigned int index = SUBREG_BYTE (src).to_constant () / mode_size;
       unsigned int num = smode == DImode && !TARGET_VECTOR_ELEN_64 ? 2 : 1;
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr111486.c 
b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr111486.c
new file mode 100644
index 00000000000..2ba2a363399
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr111486.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64iv -mabi=lp64d -O2" } */
+
+typedef char __attribute__((__vector_size__ (1))) V;
+
+V
+foo (V v, long x)
+{
+  x &= v[0];
+  return v + (char) x;
+}
-- 
2.36.3