Hi!
The recent addition of gcc_assert (regno < endregno); triggers during
glibc build on m68k.
The problem is that RA decisions shouldn't depend on expressions in
DEBUG_INSNs and those expressions can contain paradoxical subregs of certain
pseudos. If RA then decides to allocate the pseudo to a register
with very small hard register REGNO, we can trigger the new assert,
as (int) subreg_regno_offset may be negative on big endian and the small
REGNO + the negative offset can wrap around.
The following patch in that case records the range from the REGNO 0 to
endregno, before the addition of the assert as both regno and endregno are
unsigned it wouldn't record anything at all silently.
Bootstrapped/regtested on x86_64-linux and i686-linux and tested with a
cross compiler to m68k-liux on the testcase, ok for trunk?
2021-06-24 Jakub Jelinek <ja...@redhat.com>
PR middle-end/101170
* df-scan.c (df_ref_record): For paradoxical big-endian SUBREGs
where regno + subreg_regno_offset wraps around use 0 as starting
regno.
* gcc.dg/pr101170.c: New test.
--- gcc/df-scan.c.jj 2021-06-22 10:04:46.371208994 +0200
+++ gcc/df-scan.c 2021-06-23 12:46:51.654678805 +0200
@@ -2576,9 +2576,21 @@ df_ref_record (enum df_ref_class cl,
if (GET_CODE (reg) == SUBREG)
{
- regno += subreg_regno_offset (regno, GET_MODE (SUBREG_REG (reg)),
- SUBREG_BYTE (reg), GET_MODE (reg));
- endregno = regno + subreg_nregs (reg);
+ int off = subreg_regno_offset (regno, GET_MODE (SUBREG_REG (reg)),
+ SUBREG_BYTE (reg), GET_MODE (reg));
+ unsigned int nregno = regno + off;
+ endregno = nregno + subreg_nregs (reg);
+ if (off < 0 && regno < (unsigned) -off)
+ /* Deal with paradoxical SUBREGs on big endian where
+ in debug insns the hard reg number might be smaller
+ than -off, such as (subreg:DI (reg:SI 0 [+4 ]) 0));
+ RA decisions shouldn't be affected by debug insns
+ and so RA can decide to put pseudo into a hard reg
+ with small REGNO, even when it is referenced in
+ a paradoxical SUBREG in a debug insn. */
+ regno = 0;
+ else
+ regno = nregno;
}
else
endregno = END_REGNO (reg);
--- gcc/testsuite/gcc.dg/pr101170.c.jj 2021-06-23 12:27:08.866593960 +0200
+++ gcc/testsuite/gcc.dg/pr101170.c 2021-06-23 12:26:55.823769555 +0200
@@ -0,0 +1,37 @@
+/* PR middle-end/101170 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -g" } */
+
+#include <stdarg.h>
+
+struct S { int a; int b[4]; } s;
+va_list ap;
+int i;
+long long l;
+
+struct S
+foo (int x)
+{
+ struct S a = {};
+ do
+ if (x)
+ return a;
+ while (1);
+}
+
+__attribute__((noipa)) void
+bar (void)
+{
+ for (; i; i++)
+ l |= va_arg (ap, long long) << s.b[i];
+ if (l)
+ foo (l);
+}
+
+void
+baz (int v, ...)
+{
+ va_start (ap, v);
+ bar ();
+ va_end (ap);
+}
Jakub
