https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91446
Bug ID: 91446
Summary: Wrong cost for scalar_load/scalar_store of vector type
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: hjl.tools at gmail dot com
Target Milestone: ---
Target: i386
[hjl@gnu-skx-1 skx-3]$ cat x.i
typedef struct
{
unsigned long width, height;
long x, y;
} info;
extern void bar (info *);
void
foo (unsigned long width, unsigned long height, long x, long y)
{
info t;
t.width = width;
t.height = height;
t.x = x;
t.y = y;
bar (&t);
}
[hjl@gnu-skx-1 skx-3]$ make x.s
/export/build/gnu/tools-build/gcc-tuning-debug/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/tools-build/gcc-tuning-debug/build-x86_64-linux/gcc/ -Ofast
-march=skylake-avx512 -S x.i
[hjl@gnu-skx-1 skx-3]$ cat x.s
.file "x.i"
.text
.p2align 4
.globl foo
.type foo, @function
foo:
.LFB0:
.cfi_startproc
subq $40, %rsp
.cfi_def_cfa_offset 48
movq %rdi, (%rsp)
movq %rsp, %rdi
movq %rsi, 8(%rsp)
movq %rdx, 16(%rsp)
movq %rcx, 24(%rsp)
call bar
addq $40, %rsp
.cfi_def_cfa_offset 8
ret
.cfi_endproc
.LFE0:
.size foo, .-foo
.ident "GCC: (GNU) 10.0.0 20190812 (experimental)"
.section .note.GNU-stack,"",@progbits
[hjl@gnu-skx-1 skx-3]$
The problem is
(gdb) f 0
#0 ix86_builtin_vectorization_cost (type_of_cost=scalar_store,
vectype=0x7fffea63abd0)
at /export/gnu/import/git/intel/gcc-tuning/gcc/config/i386/i386.c:21090
21090 : ix86_cost->int_store [2]) / 2;
(gdb) p mode
$7 = E_V2DImode
(gdb)
case scalar_load:
/* load/store costs are relative to register move which is 2. Recompute
it to COSTS_N_INSNS so everything have same base. */
return COSTS_N_INSNS (fp ? ix86_cost->sse_load[0]
: ix86_cost->int_load [2]) / 2;
case scalar_store:
return COSTS_N_INSNS (fp ? ix86_cost->sse_store[0]
: ix86_cost->int_store [2]) / 2;
2 DImode stores/loads are needed to store/load V2DImode.
