https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116229
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2024-08-04
Ever confirmed|0 |1
Target Milestone|--- |15.0
Status|UNCONFIRMED |NEW
Summary|wrong code at -Ofast |[15 Regression] wrong code
|aarch64 due to missing fneg |at -Ofast aarch64 due to
|to generate |missing fneg to generate
|0x8000000000000000 |0x8000000000000000
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Reduced a little further:
```
typedef __attribute__((__vector_size__ (8))) unsigned long V;
V __attribute__((__noipa__))
foo (void)
{
return (V){ 0x8000000000000000 };
}
V ref = (V){ 0x8000000000000000 };
int
main ()
{
V v = foo ();
if (v[0] != ref[0])
__builtin_abort();
}
```
Late_combine2 does:
```
trying to combine definition of r32 in:
13: v0:V4SI=const_vector
into:
14: v0:V2DF=-v0:V2DF
successfully matched this instruction to *aarch64_simd_movv2df:
(set (reg:V2DF 32 v0)
(const_vector:V2DF [
(const_double:DF -0.0 [-0x0.0p+0]) repeated x2
]))
```
Which is correct if it was V2DF but the issue is how split of:
```
(insn 10 5 11 2 (set (reg:DI 32 v0)
(const_int -9223372036854775808 [0x8000000000000000]))
"/app/example.cpp":7:1 -1
(expr_list:REG_EQUAL (const_int -9223372036854775808 [0x8000000000000000])
(nil)))
```
into:
```
(insn 13 5 14 2 (set (reg:V4SI 32 v0)
(const_vector:V4SI [
(const_int 0 [0]) repeated x4
])) "/app/example.cpp":7:1 -1
(nil))
(insn 14 13 11 2 (set (reg:V2DF 32 v0)
(neg:V2DF (reg:V2DF 32 v0))) "/app/example.cpp":7:1 -1
(nil))
```
Via `Splitting with gen_split_10 (aarch64.md:1488)` .
