[Bug target/41993] [sh] ICE in create_pre_exit, at mode-switching.c:399

[ubizjak at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41993



--- Comment #4 from Uros Bizjak <ubizjak at gmail dot com> 2012-11-04 16:45:51 
UTC ---

I have looked a bit into this problem, since AVX vzeroupper insertion now

depends on MODE_EXIT functionality. IMO, the patch in Comment #1 is correct for

all optimization levels. The reason, the problem is triggered only at -O0 is

that since __builtin_return loads from the memory, gcc emits offsets to memory

locations using the pseudo:



...



(insn 9 8 11 2 (set (reg:SI 0 r0)

        (mem:SI (reg/f:SI 163) [0 S4 A8])) pr41933.c:3 238 {movsi_ie}

     (nil))

(insn 11 9 12 2 (set (reg:SI 165)

        (mem/f/c:SI (plus:SI (reg/f:SI 162)

                (const_int 60 [0x3c])) [0 rframe+0 S4 A32])) pr41933.c:3 238

{movsi_ie}

     (nil))

(insn 12 11 13 2 (set (reg/f:SI 164)

        (plus:SI (reg:SI 165)

            (const_int 4 [0x4]))) pr41933.c:3 62 {*addsi3_compact}

     (nil))

(insn 13 12 10 2 (set (reg:SI 64 fr0)

        (mem:SI (reg/f:SI 164) [0 S4 A8])) pr41933.c:3 238 {movsi_ie}

     (nil))

(insn 10 13 14 2 (use (reg:SI 0 r0)) pr41933.c:3 -1

     (nil))

(insn 14 10 22 2 (use (reg:SI 64 fr0)) pr41933.c:3 -1

     (nil))

(insn 22 14 0 2 (use (reg/i:SI 0 r0)) pr41933.c:4 -1

     (nil))



This additional pseudo is what breaks the compilation. At -O2, we enter

mode-switching with:



(note 4 1 2 2 [bb 2] NOTE_INSN_BASIC_BLOCK)

(insn 2 4 3 2 (set (reg/v/f:SI 161 [ rframe ])

        (reg:SI 4 r4 [ rframe ])) pr41933.c:2 238 {movsi_ie}

     (expr_list:REG_DEAD (reg:SI 4 r4 [ rframe ])

        (nil)))

(note 3 2 6 2 NOTE_INSN_FUNCTION_BEG)

(insn 6 3 8 2 (set (reg:SI 0 r0)

        (mem:SI (reg/v/f:SI 161 [ rframe ]) [0 S4 A8])) pr41933.c:3 238

{movsi_ie}

     (nil))

(insn 8 6 7 2 (set (reg:SI 64 fr0)

        (mem:SI (plus:SI (reg/v/f:SI 161 [ rframe ])

                (const_int 4 [0x4])) [0 S4 A8])) pr41933.c:3 238 {movsi_ie}

     (expr_list:REG_DEAD (reg/v/f:SI 161 [ rframe ])

        (nil)))

(insn 7 8 9 2 (use (reg:SI 0 r0)) pr41933.c:3 -1

     (nil))

(insn 9 7 17 2 (use (reg:SI 64 fr0)) pr41933.c:3 -1

     (expr_list:REG_DEAD (reg:SI 64 fr0)

        (nil)))

(insn 17 9 0 2 (use (reg/i:SI 0 r0)) pr41933.c:4 -1

     (nil))



In this case, we found many return registers (due to __builtin_return), and

consequently lowered nregs to zero. This satisfies the following assert in

(!nregs) and (nregs != hard_regno_nregs[ret_start][GET_MODE (ret_reg)]) cases.



In -O0 case, we broke discovery loop too early, so we can't find all return

regs. I would argue, that we should ignore non-relevant pseudos with:



--cut here--

Index: mode-switching.c

===================================================================

--- mode-switching.c    (revision 193133)

+++ mode-switching.c    (working copy)

@@ -324,7 +324,10 @@ create_pre_exit (int n_entities, int *entity_map,

                    else

                      break;

                    if (copy_start >= FIRST_PSEUDO_REGISTER)

-                     break;

+                     {

+                       last_insn = return_copy;

+                       continue;

+                     }

                    copy_num

                      = hard_regno_nregs[copy_start][GET_MODE (copy_reg)];



--cut here--



In the same way as in case of i.e. UNSPEC_VOLATILE in the preceeding code.