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Re: [PATCH] Fix expansion of comparisons into signed type with 1-bit precision (PR middle-end/48973)
On Mon, May 23, 2011 at 6:21 AM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Mon, May 23, 2011 at 06:06:55AM -0700, H.J. Lu wrote:
>> On Thu, May 12, 2011 at 7:36 AM, Jakub Jelinek <jakub@redhat.com> wrote:
>> > The read from a 1-bit signed bitfield initialized by a comparison
>> > is optimized into the comparison, which has that 1-bit signed bitfield
>> > comparison. ?Unfortunately that is still expanded as setting the result
>> > to 0 resp. 1 instead of this case 0 resp. -1 QImode pseudo, which is then
>> > sign extended into SImode for the comparison.
>> >
>> > Fixed by special casing expansion in that case. ?I think it is rare enough
>> > we can just ignore the fold_single_bit_test optimization in that case,
>> > rather than having two versions thereof.
>> >
>> > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk/4.6?
>> >
>> > 2011-05-12 ?Jakub Jelinek ?<jakub@redhat.com>
>> >
>> > ? ? ? ?PR middle-end/48973
>> > ? ? ? ?* expr.c (expand_expr_real_2) <case LT_EXPR>: If do_store_flag
>> > ? ? ? ?failed and the comparison has a single bit signed type, use
>> > ? ? ? ?constm1_rtx instead of const1_rtx for true value.
>> > ? ? ? ?(do_store_flag): If ops->type is single bit signed type, disable
>> > ? ? ? ?signel bit test optimization and pass -1 instead of 1 as last
>> > ? ? ? ?parameter to emit_store_flag_force.
>> >
>> > ? ? ? ?* gcc.c-torture/execute/pr48973-1.c: New test.
>> > ? ? ? ?* gcc.c-torture/execute/pr48973-2.c: New test.
>> >
>>
>> This caused:
>>
>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49123
>
> Can't reproduce, all tests succeed just fine, both on the trunk and in 4.6,
> both x86_64-linux {-m32,-m64} and 32-bit HWI i686-linux, including -flto.
>
Does your linker support LTO?
--
H.J.