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8b5919bae1
The builtin-clear-padding-6.c testcase fails as clear_padding_type
doesn't correctly recompute the buf->size and buf->off members after
expanding clearing of an array using a runtime loop.
buf->size should be in that case the offset after which it should continue
with next members or padding before them modulo UNITS_PER_WORD and
buf->off that offset minus buf->size. That is what the code was doing,
but with off being the start of the loop cleared array, not its end.
So, the last hunk in gimple-fold.cc fixes that.
When adding the testcase, I've noticed that the
c-c++-common/torture/builtin-clear-padding-* tests, although clearly
written as runtime tests to test the builtins at runtime, didn't have
{ dg-do run } directive and were just compile tests because of that.
When adding that to the tests, builtin-clear-padding-1.c was already
failing without that clear_padding_type hunk too, but
builtin-clear-padding-5.c was still failing even after the change.
That is due to a bug in clear_padding_flush which the patch fixes as
well - when clear_padding_flush is called with full=true (that happens
at the end of the whole __builtin_clear_padding or on those array
padding clears done by a runtime loop), it wants to flush all the pending
padding clearings rather than just some. If it is at the end of the whole
object, it decreases wordsize when needed to make sure the code never writes
including RMW cycles to something outside of the object:
if ((unsigned HOST_WIDE_INT) (buf->off + i + wordsize)
> (unsigned HOST_WIDE_INT) buf->sz)
{
gcc_assert (wordsize > 1);
wordsize /= 2;
i -= wordsize;
continue;
}
but if it is full==true flush in the middle, this doesn't happen, but we
still process just the buffer bytes before the current end. If that end
is not on a wordsize boundary, e.g. on the builtin-clear-padding-5.c test
the last chunk is 2 bytes, '\0', '\xff', i is 16 and end is 18,
nonzero_last might be equal to the end - i, i.e. 2 here, but still all_ones
might be true, so in some spots we just didn't emit any clearing in that
last chunk.
2024-07-17 Jakub Jelinek <jakub@redhat.com>
PR middle-end/115527
* gimple-fold.cc (clear_padding_flush): Introduce endsize
variable and use it instead of wordsize when comparing it against
nonzero_last.
(clear_padding_type): Increment off by sz.
* c-c++-common/torture/builtin-clear-padding-1.c: Add dg-do run
directive.
* c-c++-common/torture/builtin-clear-padding-2.c: Likewise.
* c-c++-common/torture/builtin-clear-padding-3.c: Likewise.
* c-c++-common/torture/builtin-clear-padding-4.c: Likewise.
* c-c++-common/torture/builtin-clear-padding-5.c: Likewise.
* c-c++-common/torture/builtin-clear-padding-6.c: New test.
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