[PATCH v2 2/2] emit-rtl: Validate mode for paradoxical hardware subregs [PR119966]

[Dimitar Dimitrov]

After r16-160-ge6f89d78c1a752, late_combine2 started transforming the
following RTL for pru-unknown-elf:

  (insn 3949 3948 3951 255 (set (reg:QI 56 r14.b0 [orig:1856 _619 ] [1856])
          (and:QI (reg:QI 1 r0.b1 [orig:1855 _201 ] [1855])
              (const_int 3 [0x3])))
       (nil))
  ...
  (insn 3961 7067 3962 255 (set (reg:SI 56 r14.b0)
          (zero_extend:SI (reg:QI 56 r14.b0 [orig:1856 _619 ] [1856])))
       (nil))

into:

  (insn 3961 7067 3962 255 (set (reg:SI 56 r14.b0)
          (and:SI (subreg:SI (reg:QI 1 r0.b1 [orig:1855 _201 ] [1855]) 0)
              (const_int 3 [0x3])))
       (nil))

That caused libbacktrace build to break for pru-unknown-elf.  Register
r0.b1 (regno 1) is not valid for SImode, which validate_subreg failed to
reject.

Fix by calling HARD_REGNO_MODE_OK to ensure that both inner and outer
modes are valid for the hardware subreg.

This patch fixes the broken PRU toolchain build.  It leaves only two
test case regressions for PRU, caused by rnreg pass renaming a valid
paradoxical subreg into an invalid one.
  gcc.c-torture/execute/20040709-1.c
  gcc.c-torture/execute/20040709-2.c

        PR target/119966

gcc/ChangeLog:

        * emit-rtl.cc (validate_subreg): Validate inner
        and outer mode for paradoxical hardware subregs.

Co-authored-by: Andrew Pinski <pins...@gmail.com>
Signed-off-by: Dimitar Dimitrov <dimi...@dinux.eu>
---
 gcc/emit-rtl.cc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/gcc/emit-rtl.cc b/gcc/emit-rtl.cc
index e46b0f9eac4..6c5d9b55508 100644
--- a/gcc/emit-rtl.cc
+++ b/gcc/emit-rtl.cc
@@ -983,6 +983,9 @@ validate_subreg (machine_mode omode, machine_mode imode,
       if ((COMPLEX_MODE_P (imode) || VECTOR_MODE_P (imode))
          && GET_MODE_INNER (imode) == omode)
        ;
+      else if (!targetm.hard_regno_mode_ok (regno, imode)
+              || !targetm.hard_regno_mode_ok (regno, omode))
+       return false;
       else if (!REG_CAN_CHANGE_MODE_P (regno, imode, omode))
        return false;
 
-- 
2.49.0