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jump: Also handle jumps wrapped in UNSPEC or UNSPEC_VOLATILE

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VAX has interlocked branch instructions used for atomic operations and
we want to have them wrapped in UNSPEC_VOLATILE so as not to have code
carried across.  This however breaks with jump optimization and leads
to an ICE in the build of libbacktrace like:

.../libbacktrace/mmap.c:190:1: internal compiler error: in fixup_reorder_chain, at cfgrtl.c:3934
  190 | }
      | ^
0x1087d46b fixup_reorder_chain
	.../gcc/cfgrtl.c:3934
0x1087f29f cfg_layout_finalize()
	.../gcc/cfgrtl.c:4447
0x1087c74f execute
	.../gcc/cfgrtl.c:3662

on RTL like:

(jump_insn 18 17 150 4 (unspec_volatile [
            (set (pc)
                (if_then_else (eq (zero_extract:SI (mem/v:SI (reg/f:SI 23 [ _2 ]) [-1  S4 A32])
                            (const_int 1 [0x1])
                            (const_int 0 [0]))
                        (const_int 1 [0x1]))
                    (label_ref 20)
                    (pc)))
            (set (zero_extract:SI (mem/v:SI (reg/f:SI 23 [ _2 ]) [-1  S4 A32])
                    (const_int 1 [0x1])
                    (const_int 0 [0]))
                (const_int 1 [0x1]))
        ] 101) ".../libbacktrace/mmap.c":135:14 158 {jbbssisi}
     (nil)
 -> 20)

when those branches are enabled with a follow-up change.  Also showing
with:

FAIL: gcc.dg/pr61756.c (internal compiler error)

Handle branches wrapped in UNSPEC_VOLATILE then and, for consistency,
also in UNSPEC.  The presence of UNSPEC_VOLATILE will prevent such
branches from being removed as they won't be accepted by `onlyjump_p',
we just need to let them through.

	gcc/
	* jump.c (pc_set): Also accept a jump wrapped in UNSPEC or
	UNSPEC_VOLATILE.
	(any_uncondjump_p, any_condjump_p): Update comment accordingly.
This commit is contained in:
Maciej W. Rozycki 2020-12-05 18:26:25 +00:00
parent 4b70b2e07a
commit 630c9a4d54
1 changed files with 17 additions and 7 deletions
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24
gcc/jump.c
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@ -850,9 +850,17 @@ pc_set (const rtx_insn *insn)
pat = PATTERN (insn);
/* The set is allowed to appear either as the insn pattern or
the first set in a PARALLEL. */
if (GET_CODE (pat) == PARALLEL)
pat = XVECEXP (pat, 0, 0);
the first set in a PARALLEL, UNSPEC or UNSPEC_VOLATILE. */
switch (GET_CODE (pat))
{
case PARALLEL:
case UNSPEC:
case UNSPEC_VOLATILE:
pat = XVECEXP (pat, 0, 0);
break;
default:
break;
}
if (GET_CODE (pat) == SET && GET_CODE (SET_DEST (pat)) == PC)
return pat;
@ -860,7 +868,9 @@ pc_set (const rtx_insn *insn)
}
/* Return true when insn is an unconditional direct jump,
possibly bundled inside a PARALLEL. */
possibly bundled inside a PARALLEL, UNSPEC or UNSPEC_VOLATILE.
The instruction may have various other effects so before removing the jump
you must verify onlyjump_p. */
int
any_uncondjump_p (const rtx_insn *insn)
@ -876,9 +886,9 @@ any_uncondjump_p (const rtx_insn *insn)
}
/* Return true when insn is a conditional jump. This function works for
instructions containing PC sets in PARALLELs. The instruction may have
various other effects so before removing the jump you must verify
onlyjump_p.
instructions containing PC sets in PARALLELs, UNSPECs or UNSPEC_VOLATILEs.
The instruction may have various other effects so before removing the jump
you must verify onlyjump_p.
Note that unlike condjump_p it returns false for unconditional jumps. */