Hi Suwa-san,
On Tue, Jan 17, 2023 at 9:25 PM Takayuki 'January June' Suwa
<[email protected]> wrote:
>
> Register-register move instructions that can be easily seen as
> unnecessary by the human eye may remain in the compiled result.
> For example:
>
> /* example */
> double test(double a, double b) {
> return __builtin_copysign(a, b);
> }
>
> test:
> add.n a3, a3, a3
> extui a5, a5, 31, 1
> ssai 1
> ;; be in the same BB
> src a7, a5, a3 ;; No '0' in the source constraints
> ;; No CALL insns in this span
> ;; Both A3 and A7 are irrelevant to
> ;; insns in this span
> mov.n a3, a7 ;; An unnecessary reg-reg move
> ;; A7 is not used after this
> ret.n
>
> The last two instructions above, excluding the return instruction,
> could be done like this:
>
> src a3, a5, a3
>
> This symptom often occurs when handling DI/DFmode values with SImode
> instructions. This patch solves the above problem using peephole2
> pattern.
>
> gcc/ChangeLog:
>
> * config/xtensa/xtensa.md: New peephole2 pattern that eliminates
> the occurrence of genral-purpose register used only once and for
> transferring intermediate value.
> ---
> gcc/config/xtensa/xtensa.md | 43 +++++++++++++++++++++++++++++++++++++
> 1 file changed, 43 insertions(+)
This still generates ICE, this time while building libstdc++:
during RTL pass: ce3
In file included from
build/xtensa-buildroot-linux-uclibc/libstdc++-v3/include/bits/locale_facets.h:2687,
from
build/xtensa-buildroot-linux-uclibc/libstdc++-v3/include/locale:42,
from gcc/libstdc++-v3/src/c++11/locale-inst.cc:38,
from gcc/libstdc++-v3/src/c++11/wlocale-inst.cc:35:
build/xtensa-buildroot-linux-uclibc/libstdc++-v3/include/bits/locale_facets.tcc:
In member function ‘_InIter std::num_get<_CharT,
_InIter>::do_get(iter_type, iter_type, std::ios_base&,
std::ios_base::iostate&, bool&) const [with _CharT = wchar_t; _InIter
= std::istreamb
uf_iterator<wchar_t, std::char_traits<wchar_t> >]’:
build/xtensa-buildroot-linux-uclibc/libstdc++-v3/include/bits/locale_facets.tcc:686:5:
internal compiler error: in df_refs_verify, at df-scan.cc:4009
686 | }
| ^
0x6eb0dc df_refs_verify
gcc/gcc/df-scan.cc:4009
0xd19a74 df_insn_refs_verify
gcc/gcc/df-scan.cc:4092
0xd1b94c df_bb_verify
gcc/gcc/df-scan.cc:4125
0xd1bd77 df_scan_verify()
gcc/gcc/df-scan.cc:4246
0xd06ca7 df_verify()
gcc/gcc/df-core.cc:1818
0xd06ca7 df_analyze_1
gcc/gcc/df-core.cc:1214
0x1a7287c if_convert
gcc/gcc/ifcvt.cc:5858
0x1a73ddd execute
gcc/gcc/ifcvt.cc:6026
--
Thanks.
-- Max
