Fix PR rtl-optimization/102306
Commit Message
Hi,
this is a duplication of volatile loads introduced during GCC 9 development by
the new 2->2 mechanism of the RTL combiner. There is already a substantial
checking for volatile references in can_combine_p but it implicitly assumes
that the combination reduces the number of instructions, which is of course
not the case here. So the fix teaches try_combine to abort the combination
when it is about to make a copy of volatile references to preserve them.
Bootstrapped/regtested on x86-64/Linux, OK for mainline and release branches?
2021-09-16 Eric Botcazou <ebotcazou@adacore.com>
PR rtl-optimization/102306
* combine.c (try_combine): Abort the combination if we are about
to duplicate volatile references.
2021-09-16 Eric Botcazou <ebotcazou@adacore.com>
* gcc.target/sparc/20210916-1.c: New test.
Comments
On 9/16/2021 3:02 AM, Eric Botcazou wrote:
> Hi,
>
> this is a duplication of volatile loads introduced during GCC 9 development by
> the new 2->2 mechanism of the RTL combiner. There is already a substantial
> checking for volatile references in can_combine_p but it implicitly assumes
> that the combination reduces the number of instructions, which is of course
> not the case here. So the fix teaches try_combine to abort the combination
> when it is about to make a copy of volatile references to preserve them.
>
> Bootstrapped/regtested on x86-64/Linux, OK for mainline and release branches?
>
>
> 2021-09-16 Eric Botcazou <ebotcazou@adacore.com>
>
> PR rtl-optimization/102306
> * combine.c (try_combine): Abort the combination if we are about
> to duplicate volatile references.
>
>
> 2021-09-16 Eric Botcazou <ebotcazou@adacore.com>
>
> * gcc.target/sparc/20210916-1.c: New test.
OK
jeff
@@ -3063,6 +3063,16 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
return 0;
}
+ /* We cannot safely duplicate volatile references in any case. */
+
+ if ((added_sets_2 && volatile_refs_p (PATTERN (i2)))
+ || (added_sets_1 && volatile_refs_p (PATTERN (i1)))
+ || (added_sets_0 && volatile_refs_p (PATTERN (i0))))
+ {
+ undo_all ();
+ return 0;
+ }
+
/* Count how many auto_inc expressions there were in the original insns;
we need to have the same number in the resulting patterns. */