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[patch] Fix SSA_NAME_OCCURS_IN_ABNORMAL_PHI issue in backprop
- From: Eric Botcazou <ebotcazou at adacore dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Mon, 08 Feb 2016 11:37:07 +0100
- Subject: [patch] Fix SSA_NAME_OCCURS_IN_ABNORMAL_PHI issue in backprop
- Authentication-results: sourceware.org; auth=none
Hi,
the Ada runtime fails to build for platforms still using the old SJLJ scheme
because of the new GIMPLE backprop pass (hence it's a regression):
eric@polaris:~/build/gcc/native> gcc/gnat1 -quiet a-ncelfu.ads -gnatpg -O -I
~/svn/gcc/gcc/ada/
a-ngcefu.adb: In function 'Ada.Numerics.Complex_Elementary_Functions.Sqrt':
a-ngcefu.adb:16:4: error: SSA_NAME_OCCURS_IN_ABNORMAL_PHI should be set
for SSA_NAME: _28 in statement:
xr_3(ab) = PHI <xr_22(D)(ab)(2), xr_22(D)(ab)(3), xr_22(D)(ab)(4), _28(5),
_28(6), _28(7), xr_4(ab)(11), xr_4(ab)(12), xr_4(ab)(14), xr_4(ab)(15),
xr_4(ab)(16), xr_4(ab)(17), xr_4(ab)(18), xr_4(ab)(19), xr_4(ab)(20), xr_4(ab)
(21), xr_4(ab)(22), xr_4(ab)(23), xr_4(ab)(24), xr_4(ab)(25), xr_4(ab)(26),
xr_4(ab)(27), xr_4(ab)(28), xr_4(ab)(29), xr_4(ab)(30), xr_4(ab)(32), xr_4(ab)
(34), xr_4(ab)(36), xr_4(ab)(37)>
PHI argument
_28
for PHI node
xr_3(ab) = PHI <xr_22(D)(ab)(2), xr_22(D)(ab)(3), xr_22(D)(ab)(4), _28(5),
_28(6), _28(7), xr_4(ab)(11), xr_4(ab)(12), xr_4(ab)(14), xr_4(ab)(15),
xr_4(ab)(16), xr_4(ab)(17), xr_4(ab)(18), xr_4(ab)(19), xr_4(ab)(20), xr_4(ab)
(21), xr_4(ab)(22), xr_4(ab)(23), xr_4(ab)(24), xr_4(ab)(25), xr_4(ab)(26),
xr_4(ab)(27), xr_4(ab)(28), xr_4(ab)(29), xr_4(ab)(30), xr_4(ab)(32), xr_4(ab)
(34), xr_4(ab)(36), xr_4(ab)(37)>
+===========================GNAT BUG DETECTED==============================+
| 6.0.0 20160206 (experimental) [trunk revision 233194] (x86_64-suse-linux)
GCC error:|
| verify_ssa failed |
| Error detected around a-ngcefu.adb:16:4
The problem is that the pass propagates the source RHS (_28) of:
xr_29(ab) = ABS_EXPR <_28>;
into a PHI note using xr_29 along an AB edge so the above check triggers.
I think replacing such an AB SSA_NAME is problematic in any case: if the RHS
is not AB, then the check triggers; if the RHS is also AB, then we may create
overlapping live ranges and the compilation will abort later. We can probably
create a new SSA_NAME but it's not really the spirit of the backprop pass and
I'm not sure it's worth the hassle, hence the minimal attached fixlet.
Tested on x86_64-suse-linux, OK for the mainline?
2016-02-08 Eric Botcazou <ebotcazou@adacore.com>
* gimple-ssa-backprop.c (optimize_phi): Do not replace an argument
with SSA_NAME_OCCURS_IN_ABNORMAL_PHI set.
--
Eric Botcazou
Index: gimple-ssa-backprop.c
===================================================================
--- gimple-ssa-backprop.c (revision 233194)
+++ gimple-ssa-backprop.c (working copy)
@@ -840,13 +840,14 @@ backprop::optimize_phi (gphi *phi, tree
bool replaced = false;
FOR_EACH_PHI_ARG (use, phi, oi, SSA_OP_USE)
{
- tree new_arg = strip_sign_op (USE_FROM_PTR (use));
- if (new_arg)
+ tree arg = USE_FROM_PTR (use);
+ tree new_arg = strip_sign_op (arg);
+ if (new_arg && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (arg))
{
if (!replaced)
prepare_change (var);
if (dump_file && (dump_flags & TDF_DETAILS))
- note_replacement (phi, USE_FROM_PTR (use), new_arg);
+ note_replacement (phi, arg, new_arg);
replace_exp (use, new_arg);
replaced = true;
}