Hi!
Here is an alternate patch for the PR99830 bug.
As discussed on IRC and in the PR, the reason why a (clobber:TI (const_int 0))
has been propagated into the debug insns is that it got optimized away
during simplification from the i3 instruction pattern.
And that happened because
simplify_and_const_int_1 (SImode, varop, 255)
with varop of
(ashift:SI (subreg:SI (and:TI (clobber:TI (const_int 0 [0]))
(const_int 255 [0xff])) 0)
(const_int 16 [0x10]))
was called and through nonzero_bits determined that (whatever << 16) & 255
is const0_rtx.
It is, but if there are side-effects in varop and such clobbers are
considered as such, we shouldn't optimize those away.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2021-04-10 Jakub Jelinek <ja...@redhat.com>
PR debug/99830
* combine.c (simplify_and_const_int_1): Don't optimize varop
away if it has side-effects.
* gcc.dg/pr99830.c: New test.
--- gcc/combine.c.jj 2021-04-08 17:01:37.315168182 +0200
+++ gcc/combine.c 2021-04-09 22:33:56.961264092 +0200
@@ -10153,7 +10153,7 @@ simplify_and_const_int_1 (scalar_int_mod
constop &= nonzero;
/* If we don't have any bits left, return zero. */
- if (constop == 0)
+ if (constop == 0 && !side_effects_p (varop))
return const0_rtx;
/* If VAROP is a NEG of something known to be zero or 1 and CONSTOP is
--- gcc/testsuite/gcc.dg/pr99830.c.jj 2021-04-08 16:39:44.243774333 +0200
+++ gcc/testsuite/gcc.dg/pr99830.c 2021-04-08 16:28:40.463175738 +0200
@@ -0,0 +1,10 @@
+/* PR debug/99830 */
+/* { dg-do compile { target int128 } } */
+/* { dg-options "-O2 -fno-expensive-optimizations -fno-split-wide-types -g" }
*/
+
+int foo (long a, __int128 b, short c, int d, unsigned e, __int128 f)
+{
+ __builtin_memmove (2 + (char *) &f, foo, 1);
+ c >>= (char) f;
+ return c;
+}
Jakub
