In this BZ we're getting a debug compare failure. Thanks to a nice hint from
Jakub it was pretty easy to track it back to the register renaming pass which
was
making different renaming decisions based on the existence of DEBUG_INSNs.
The culprit is check_new_reg_p which potentially changes its return value in the
presence of a DEBUG_INSN in the use chain which in turn potentially changes the
renaming decisions made.
This patch arranges to always ignore DEBUG_INSNs in the chain within
check_new_reg_p and the decisions we get there are consistent.
I've bootstrapped and regression tested on x86_64, i686, ppc64le, ppc64. It's
also tested without regressions on a variety of *-elf targets and built a bunch
of *-linux-gnu cross toolchains along the way as well.
Committed to the trunk.
Jeff
commit baf3b9b2e5259558ef86bd62398e2ccecd7a4a4c
Author: Jeff Law <l...@redhat.com>
Date: Sat Apr 18 09:39:18 2020 -0600
Don't let DEBUG_INSNSs change register renaming decisions
PR debug/94439
* regrename.c (check_new_reg_p): Ignore DEBUG_INSNs when walking
the chain.
PR debug/94439
* gcc.dg/torture/pr94439.c: New test.
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index aa0902274e5..1edb5f2d70b 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2020-04-18 Jeff Law <l...@redhat.com>
+
+ PR debug/94439
+ * regrename.c (check_new_reg_p): Ignore DEBUG_INSNs when walking
+ the chain.
+
2020-04-18 Iain Buclaw <ibuc...@gdcproject.org>
* doc/sourcebuild.texi (Effective-Target Keywords, Environment
diff --git a/gcc/regrename.c b/gcc/regrename.c
index 663935b7ec1..669a6ead705 100644
--- a/gcc/regrename.c
+++ b/gcc/regrename.c
@@ -348,11 +348,17 @@ check_new_reg_p (int reg ATTRIBUTE_UNUSED, int new_reg,
/* See whether it accepts all modes that occur in
definition and uses. */
for (tmp = this_head->first; tmp; tmp = tmp->next_use)
- if ((!targetm.hard_regno_mode_ok (new_reg, GET_MODE (*tmp->loc))
- && ! DEBUG_INSN_P (tmp->insn))
- || call_clobbered_in_chain_p (this_head, GET_MODE (*tmp->loc),
- new_reg))
- return false;
+ {
+ /* Completely ignore DEBUG_INSNs, otherwise we can get
+ -fcompare-debug failures. */
+ if (DEBUG_INSN_P (tmp->insn))
+ continue;
+
+ if (!targetm.hard_regno_mode_ok (new_reg, GET_MODE (*tmp->loc))
+ || call_clobbered_in_chain_p (this_head, GET_MODE (*tmp->loc),
+ new_reg))
+ return false;
+ }
return true;
}
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index db691564bba..c2b5ddfa5cc 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-04-18 Jeff Law <l...@redhat.com>
+
+ PR debug/94439
+ * gcc.dg/torture/pr94439.c: New test.
+
2020-04-18 Iain Buclaw <ibuc...@gdcproject.org>
* gdc.dg/link.d: Use d_runtime_has_std_library effective target.
diff --git a/gcc/testsuite/gcc.dg/torture/pr94439.c
b/gcc/testsuite/gcc.dg/torture/pr94439.c
new file mode 100644
index 00000000000..a461b2f8c18
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr94439.c
@@ -0,0 +1,55 @@
+/* { dg-do compile { target i?86-*-* x86_64-*-* } } */
+/* { dg-additional-options "-flive-patching=inline-clone -funroll-loops
-fno-tree-forwprop -fno-expensive-optimizations -mstack-arg-probe
-fcompare-debug" } */
+/* { dg-skip-if "" { *-*-* } { "-flto" } { "" } } */
+
+extern void exit (int);
+extern void abort (void);
+
+#define COMPARE_BODY(A, B, TYPE, COPYSIGN) \
+ do { \
+ TYPE s1 = COPYSIGN ((TYPE) 1.0, A);
\
+ TYPE s2 = COPYSIGN ((TYPE) 1.0, B);
\
+ if (s1 != s2) \
+ abort ();
\
+ if ((__builtin_isnan (A) != 0) != (__builtin_isnan (B) != 0)) \
+ abort ();
\
+ if ((A != B) != (__builtin_isnan (A) != 0))
\
+ abort ();
\
+ } while (0)
+
+void
+comparel (long double a, long double b)
+{
+ COMPARE_BODY (a, b, long double, __builtin_copysignl);
+}
+
+void
+comparecl (_Complex long double a, long double r, long double i)
+{
+ comparel (__real__ a, r);
+ comparel (__imag__ a, i);
+}
+
+#define VERIFY(A, B, TYPE, COMPARE) \
+ do { \
+ TYPE a = A; \
+ TYPE b = B; \
+ _Complex TYPE cr = __builtin_complex (a, b); \
+ static _Complex TYPE cs = __builtin_complex (A, B); \
+ COMPARE (cr, A, B); \
+ COMPARE (cs, A, B); \
+ } while (0)
+
+#define ALL_CHECKS(PZ, NZ, NAN, INF, TYPE, COMPARE) \
+ do { \
+ VERIFY (NAN, NZ, TYPE, COMPARE); \
+ VERIFY (INF, NZ, TYPE, COMPARE); \
+ VERIFY (INF, NAN, TYPE, COMPARE); \
+ VERIFY (INF, INF, TYPE, COMPARE); \
+ } while (0)
+
+void
+check_long_double (void)
+{
+ ALL_CHECKS (0.0l, -0.0l, __builtin_nanl(""), __builtin_infl(), long double,
comparecl);
+}
