Jakub,
Attached patch handles CALL_INSN_FUNCTION_USAGE clobbers in
copyprop_hardreg_forward_1.
Terry reported a cprop_hardreg misbehaviour here (
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64154#c2 ), in the context of
trying out -fipa-ra for thumb1. The -fipa-ra flag is currently disabled for
thumb1, but due to an AFAIU unrelated issue.
The problem is that when cprop_hardreg processes a call_insn with a clobber in
CALL_INSN_FUNCTION_USAGE, the clobber is not taken into account.
So for this call instruction, the 'clobber (reg:SI 12 ip)' is ignored:
...
(call_insn 141 292 142 13
(parallel
[
(call (mem:SI
(symbol_ref:SI ("f2") [flags 0x3] <function_decl f2>)
[0 f2 S4 A32])
(const_int 0 [0]))
(use (const_int 0 [0]))
(clobber (reg:SI 14 lr))
])
vshift-3.c:119
770 {*call_insn}
(expr_list:REG_CALL_DECL (symbol_ref:SI ("f2") [flags 0x3] <function_decl f2>)
(expr_list:REG_EH_REGION (const_int 0 [0])
(nil)))
(expr_list (clobber (reg:SI 12 ip))
(nil)))
...
This results in cprop_hardreg using register ip during the call, which is
incorrect:
...
(insn (set (reg:SI 4 r4)
(reg:SI 12 ip)))
(call_insn 141 ... )
(insn (set (reg:SI 0 r0)
(reg:SI 12 ip)))
...
I have not been able to reproduce the failing code. But I was able to observe
that the clobber in CALL_INSN_FUNCTION_USAGE was ignored by
copyprop_hardreg_forward_1. My understanding is that this is a latent bug in
cprop_hardreg, uncovered by -fipa-ra.
Actually, there is code in copyprop_hardreg_forward_1 to handle clobbers in
CALL_INSN_FUNCTION_USAGE, but that is part of the fix for PR57003, where we
re-apply clobbers:
...
/* If SET was seen in CALL_INSN_FUNCTION_USAGE, and SET_SRC
of the SET isn't in regs_invalidated_by_call hard reg set,
but instead among CLOBBERs on the CALL_INSN, we could wrongly
assume the value in it is still live. */
if (ksvd.ignore_set_reg)
{
note_stores (PATTERN (insn), kill_clobbered_value, vd);
for (exp = CALL_INSN_FUNCTION_USAGE (insn);
exp;
exp = XEXP (exp, 1))
{
rtx x = XEXP (exp, 0);
if (GET_CODE (x) == CLOBBER)
kill_value (SET_DEST (x), vd);
}
}
...
[ This code is related to a scenario where the called function returns one of
it's arguments and is annotated as such, but that doesn't apply to this example. ]
However, the earlier application of the clobbers just handles the clobbers in
PATTERN, not those in CALL_INSN_FUNCTION_USAGE:
...
/* Within asms, a clobber cannot overlap inputs or outputs.
I wouldn't think this were true for regular insns, but
scan_rtx treats them like that... */
note_stores (PATTERN (insn), kill_clobbered_value, vd);
...
This patch basically adds the same CALL_INSN_FUNCTION_USAGE for loop after the
earlier 'note_stores (PATTERN (insn), kill_clobbered_value, vd)' call.
Terry reported that the patch fixes the problem for him.
Bootstrapped and reg-tested on x86_64, no issues found.
OK for stage3 trunk?
Thanks,
- Tom
2015-01-09 Tom de Vries <t...@codesourcery.com>
PR rtl-optimization/64539
* regcprop.c (copyprop_hardreg_forward_1): Handle clobbers in
CALL_INSN_FUNCTION_USAGE.
---
gcc/regcprop.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/gcc/regcprop.c b/gcc/regcprop.c
index 8c4f564..b42a4b7 100644
--- a/gcc/regcprop.c
+++ b/gcc/regcprop.c
@@ -801,6 +801,18 @@ copyprop_hardreg_forward_1 (basic_block bb, struct value_data *vd)
I wouldn't think this were true for regular insns, but
scan_rtx treats them like that... */
note_stores (PATTERN (insn), kill_clobbered_value, vd);
+ if (CALL_P (insn))
+ {
+ rtx exp;
+ for (exp = CALL_INSN_FUNCTION_USAGE (insn);
+ exp;
+ exp = XEXP (exp, 1))
+ {
+ rtx x = XEXP (exp, 0);
+ if (GET_CODE (x) == CLOBBER)
+ kill_value (SET_DEST (x), vd);
+ }
+ }
/* Kill all auto-incremented values. */
/* ??? REG_INC is useless, since stack pushes aren't done that way. */
--
1.9.1
