[PATCH] genrecog: Add SUBREG_BYTE.to_constant check to the genrecog

[Juzhe-Zhong]

Hi, there is genrecog issue happens in RISC-V backend.

This is the ICE info:

0xfa3ba4 poly_int_pod<2u, unsigned short>::to_constant() const
        ../../../riscv-gcc/gcc/poly-int.h:504
0x28eaa91 recog_5
        ../../../riscv-gcc/gcc/config/riscv/bitmanip.md:314
0x28ec5b4 recog_7
        ../../../riscv-gcc/gcc/config/riscv/iterators.md:81
0x2a2e740 recog_436
        ../../../riscv-gcc/gcc/config/riscv/thead.md:265
0x2a729ef recog_475
        ../../../riscv-gcc/gcc/config/riscv/sync.md:509
0x2a75aec recog(rtx_def*, rtx_insn*, int*)
        ../../../riscv-gcc/gcc/config/riscv/iterators.md:55
0x2b3e39e recog_for_combine_1
        ../../../riscv-gcc/gcc/combine.cc:11382
0x2b3f457 recog_for_combine
        ../../../riscv-gcc/gcc/combine.cc:11652
0x2b25a15 try_combine
        ../../../riscv-gcc/gcc/combine.cc:4054
0x2b1d3f1 combine_instructions
        ../../../riscv-gcc/gcc/combine.cc:1266
0x2b48cfc rest_of_handle_combine
        ../../../riscv-gcc/gcc/combine.cc:15063
0x2b48db8 execute
        ../../../riscv-gcc/gcc/combine.cc:15107

This is because the genrecog code here cause ICE for scalable vector in RISC-V:

Before this patch:

static int
recog_5 (rtx x1 ATTRIBUTE_UNUSED,
        rtx_insn *insn ATTRIBUTE_UNUSED,
        int *pnum_clobbers ATTRIBUTE_UNUSED)
{
  rtx * const operands ATTRIBUTE_UNUSED = &recog_data.operand[0];
  rtx x2, x3, x4;
  int res ATTRIBUTE_UNUSED;
  if (pnum_clobbers == NULL)
    return -1;
  x2 = XEXP (x1, 1);
  x3 = XEXP (x2, 0);
  if (maybe_ne (SUBREG_BYTE (x3).to_constant (), 0) ---> this code cause ICE.
      || GET_MODE (x3) != E_SImode
      || !register_operand (operands[0], E_DImode)
      || GET_MODE (x2) != E_DImode)
    return -1;
...

This ICE happens since we have following RTL IR:

(insn 27 26 29 4 (set (reg:RVVM1HI 155 [ vect__12.23 ])
        (sign_extend:RVVM1HI (subreg:RVVMF2QI (reg:RVVMF2x2QI 146 [ 
vect_array.19 ]) [8, 8]))) "auto.c":29:1 discrim 2 12570 
{extendrvvmf2qirvvm1hi2}
     (expr_list:REG_DEAD (reg:RVVMF2x2QI 146 [ vect_array.19 ])
        (nil)))

This is the scalable vector with SUBREG_BYTE = poly (8, 8)

After this patch:

static int
recog_5 (rtx x1 ATTRIBUTE_UNUSED,
        rtx_insn *insn ATTRIBUTE_UNUSED,
        int *pnum_clobbers ATTRIBUTE_UNUSED)
{
  rtx * const operands ATTRIBUTE_UNUSED = &recog_data.operand[0];
  rtx x2, x3, x4;
  int res ATTRIBUTE_UNUSED;
  if (pnum_clobbers == NULL)
    return -1;
  x2 = XEXP (x1, 1);
  x3 = XEXP (x2, 0);
  if ((SUBREG_BYTE (x3).is_constant () && maybe_ne (SUBREG_BYTE 
(x3).to_constant (), 0))   ----> change here and fix ICE.
      || GET_MODE (x3) != E_SImode
      || !register_operand (operands[0], E_DImode)
      || GET_MODE (x2) != E_DImode)
    return -1;

Does it reasonable ?

Thanks.

gcc/ChangeLog:

        * genrecog.cc (print_test): Add SUBREG_BYTE.to_constant () check.

---
 gcc/genrecog.cc | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/gcc/genrecog.cc b/gcc/genrecog.cc
index 04a5533ca4b..28884ab3985 100644
--- a/gcc/genrecog.cc
+++ b/gcc/genrecog.cc
@@ -4705,11 +4705,14 @@ print_test (output_state *os, const rtx_test &test, 
bool is_param,
       break;
 
     case rtx_test::SUBREG_FIELD:
+      printf ("(SUBREG_BYTE (");
+      print_test_rtx (os, test);
+      printf (").is_constant () && ");
       printf ("%s (", invert_p ? "maybe_ne" : "known_eq");
       print_nonbool_test (os, test);
       printf (", ");
       print_label_value (test, is_param, value);
-      printf (")");
+      printf ("))");
       break;
 
     case rtx_test::SAVED_CONST_INT:
-- 
2.36.3