https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93270
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target| |x86_64-*-*, i?86-*-*
Priority|P3 |P2
Status|UNCONFIRMED |NEW
Keywords| |wrong-code
Last reconfirmed| |2020-01-15
CC| |rguenth at gcc dot gnu.org
Ever confirmed|0 |1
Summary|[10 Regression] DSE removes |[8/9/10 Regression] DSE
|store incorrectly |removes store incorrectly
Target Milestone|--- |8.4
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
You can probably massage it to make it a very old issue by using
typedef int v4si __attribute__((vector_size(16)));
typedef union { long double value; v4si vec; } data;
void bar(data *);
void foo(long double x)
{
data m;
m.vec = (v4si) { 0,0,0,0 };
m.value = x;
bar (&m);
}
even GCC 4.8 produces
foo:
.LFB0:
.cfi_startproc
subq $24, %rsp
.cfi_def_cfa_offset 32
fldt 32(%rsp)
movq %rsp, %rdi
fstpt (%rsp)
call bar
addq $24, %rsp
.cfi_def_cfa_offset 8
ret
which looks wrong. 3.4.6 doesn't DSE here, nor does 4.0.4. But if you
use recent GCC even RTL DSE removes the store if you use -fno-tree-dse.
So the regression is much older.
Possibly other targets are affected as well.
