https://gcc.gnu.org/g:01cca42f65f25d709264fe277d25d9db3d68c437
commit r15-2712-g01cca42f65f25d709264fe277d25d9db3d68c437
Author: Andrew Pinski <quic_apin...@quicinc.com>
Date: Fri Aug 2 10:04:40 2024 -0700
IRA: Ignore debug insns for uses in split_live_ranges_for_shrink_wrap.
[PR116179]
Late_combine exposed this latent bug in split_live_ranges_for_shrink_wrap.
What it did was copy-prop regno 151 from regno 119 from:
```
(insn 2 264 3 2 (set (reg/f:DI 119 [ thisD.3697 ])
(reg:DI 151)) "/app/example.cpp":19:13 70 {*movdi_aarch64}
(expr_list:REG_DEAD (reg:DI 151)
(nil)))
```
into these insns:
```
(debug_insn 147 146 148 5 (var_location:DI thisD.3727 (reg/f:DI 119 [
thisD.3697 ])) "/app/example.cpp":21:5 -1
(nil))
....
(insn 167 166 168 7 (set (reg:DI 1 x1)
(reg/f:DI 119 [ thisD.3697 ])) "/app/example.cpp":14:21 70
{*movdi_aarch64}
(nil))
```
Both are valid things to do. The problem is
split_live_ranges_for_shrink_wrap looks at the
uses of reg 151 and with and without debugging reg 151 have a different
usage in different BBs.
The function is trying to find a splitting point for reg 151 and they are
different. In the end
this causes register allocation difference.
The fix is for split_live_ranges_for_shrink_wrap to ignore uses that were
in debug insns.
Bootstrappped and tested on x86_64-linux-gnu with no regressions.
PR rtl-optimization/116179
gcc/ChangeLog:
* ira.cc (split_live_ranges_for_shrink_wrap): For the uses loop,
only look at non-debug insns.
gcc/testsuite/ChangeLog:
* g++.dg/torture/pr116179-1.C: New test.
Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
Diff:
---
gcc/ira.cc | 5 ++++-
gcc/testsuite/g++.dg/torture/pr116179-1.C | 26 ++++++++++++++++++++++++++
2 files changed, 30 insertions(+), 1 deletion(-)
diff --git a/gcc/ira.cc b/gcc/ira.cc
index 5642aea3caae..156541df4e6c 100644
--- a/gcc/ira.cc
+++ b/gcc/ira.cc
@@ -5144,7 +5144,10 @@ split_live_ranges_for_shrink_wrap (void)
use = DF_REF_NEXT_REG (use))
{
int ubbi = DF_REF_BB (use)->index;
- if (bitmap_bit_p (reachable, ubbi))
+
+ /* Only non debug insns should be taken into account. */
+ if (NONDEBUG_INSN_P (DF_REF_INSN (use))
+ && bitmap_bit_p (reachable, ubbi))
bitmap_set_bit (need_new, ubbi);
}
last_interesting_insn = insn;
diff --git a/gcc/testsuite/g++.dg/torture/pr116179-1.C
b/gcc/testsuite/g++.dg/torture/pr116179-1.C
new file mode 100644
index 000000000000..85e63c5938f5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/torture/pr116179-1.C
@@ -0,0 +1,26 @@
+/* { dg-additional-options "-fcompare-debug" } */
+
+/* PR rtl-optimization/116179 */
+
+struct g *b;
+struct g {};
+void *operator new(__SIZE_TYPE__, void *);
+enum c {};
+struct d : g{} * e;
+c f;
+struct h {
+ g *k() {
+ d *a;
+ c i;
+ if (a || i == 0 || i == 1)
+ if (e || f)
+ return 0;
+ return new (&j) d;
+ }
+ void n();
+ g j;
+};
+void h::n() {
+ for (g *l(b), *m(b); l; l = m, m = 0)
+ k();
+}
