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.
---
gcc/jump.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)
diff --git a/gcc/jump.c b/gcc/jump.c
index 34a8f209e20..f4c735540f0 100644
--- a/gcc/jump.c
+++ b/gcc/jump.c
@@ -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 +868,7 @@ 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. */
int
any_uncondjump_p (const rtx_insn *insn)
@@ -876,9 +884,9 @@ 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. */
--
2.11.0
