On Dec 11, 2023, Richard Biener <richard.guent...@gmail.com> wrote:
> you can use .exists (&move_mode) here to ...
Aah, yeah, and that should help avoid the noisy as_a conversions too,
that I could replace with require(), or drop altogether.
>> + || (GET_MODE_BITSIZE (as_a <scalar_int_mode> (int_move_mode))
>> + != incr * BITS_PER_UNIT))
Unfortunately, here it can't quite be dropped, GET_MODE_SIZE on a
machine_mode isn't suitable for the !=, but with .require() we know it's
a scalar_int_mode and thus != on its bitsize is fine.
> I'll note that int_mode_for_size and smallest_int_mode_for_size
> are not semantically equivalent in what they can return. In
> particular it seems you are incrementing by iter_incr even when
> formerly smallest_int_mode_for_size would have returned a
> larger than necessary mode, resulting in at least inefficient
> code, copying/comparing pieces multiple times.
If we get a mode that isn't exactly the expected size, we go for
BLKmode, so it should be fine and efficient. Unless machine modes are
not powers of two multiples of BITS_PER_UNIT, then things may get a
little weird, not so much because of repeated copying/comparing, but
because of inefficiencies in the block copy/compare operations with
block sizes that are not a good fit for such hypothetical (?) GCC
targets. I guess we can cross that bridge if we ever get to it.
> So int_mode_for_size looks more correct.
*nod*. IIRC I had it at first (very long ago), and went for the
smallest_ when transitioning to the machine_mode type hierarchy revamp.
> OK with the above change.
Here's what I've regstrapped on x86_64-linux-gnu, and will install
shortly. Thanks!
smallest_int_mode_for_size may abort when the requested mode is not
available. Call int_mode_for_size instead, that signals the
unsatisfiable request in a more graceful way.
for gcc/ChangeLog
PR middle-end/112784
* expr.cc (emit_block_move_via_loop): Call int_mode_for_size
for maybe-too-wide sizes.
(emit_block_cmp_via_loop): Likewise.
for gcc/testsuite/ChangeLog
PR middle-end/112784
* gcc.target/i386/avx512cd-inline-stringops-pr112784.c: New.
---
gcc/expr.cc | 20 +++++++++-----------
.../i386/avx512cd-inline-stringops-pr112784.c | 12 ++++++++++++
2 files changed, 21 insertions(+), 11 deletions(-)
create mode 100644
gcc/testsuite/gcc.target/i386/avx512cd-inline-stringops-pr112784.c
diff --git a/gcc/expr.cc b/gcc/expr.cc
index 6da51f2aca296..076ba706537aa 100644
--- a/gcc/expr.cc
+++ b/gcc/expr.cc
@@ -2449,15 +2449,14 @@ emit_block_move_via_loop (rtx x, rtx y, rtx size,
}
emit_move_insn (iter, iter_init);
- scalar_int_mode int_move_mode
- = smallest_int_mode_for_size (incr * BITS_PER_UNIT);
- if (GET_MODE_BITSIZE (int_move_mode) != incr * BITS_PER_UNIT)
+ opt_scalar_int_mode int_move_mode
+ = int_mode_for_size (incr * BITS_PER_UNIT, 1);
+ if (!int_move_mode.exists (&move_mode)
+ || GET_MODE_BITSIZE (int_move_mode.require ()) != incr * BITS_PER_UNIT)
{
move_mode = BLKmode;
gcc_checking_assert (can_move_by_pieces (incr, align));
}
- else
- move_mode = int_move_mode;
x_addr = force_operand (XEXP (x, 0), NULL_RTX);
y_addr = force_operand (XEXP (y, 0), NULL_RTX);
@@ -2701,16 +2700,15 @@ emit_block_cmp_via_loop (rtx x, rtx y, rtx len, tree
len_type, rtx target,
iter = gen_reg_rtx (iter_mode);
emit_move_insn (iter, iter_init);
- scalar_int_mode int_cmp_mode
- = smallest_int_mode_for_size (incr * BITS_PER_UNIT);
- if (GET_MODE_BITSIZE (int_cmp_mode) != incr * BITS_PER_UNIT
- || !can_compare_p (NE, int_cmp_mode, ccp_jump))
+ opt_scalar_int_mode int_cmp_mode
+ = int_mode_for_size (incr * BITS_PER_UNIT, 1);
+ if (!int_cmp_mode.exists (&cmp_mode)
+ || GET_MODE_BITSIZE (int_cmp_mode.require ()) != incr * BITS_PER_UNIT
+ || !can_compare_p (NE, cmp_mode, ccp_jump))
{
cmp_mode = BLKmode;
gcc_checking_assert (incr != 1);
}
- else
- cmp_mode = int_cmp_mode;
/* Save the base addresses. */
x_addr = force_operand (XEXP (x, 0), NULL_RTX);
diff --git a/gcc/testsuite/gcc.target/i386/avx512cd-inline-stringops-pr112784.c
b/gcc/testsuite/gcc.target/i386/avx512cd-inline-stringops-pr112784.c
new file mode 100644
index 0000000000000..c81f99c693c24
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/avx512cd-inline-stringops-pr112784.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-mavx512cd -finline-stringops" } */
+
+struct S {
+ int e;
+} __attribute__((aligned(128)));
+
+int main() {
+ struct S s1;
+ struct S s2;
+ int v = __builtin_memcmp(&s1, &s2, sizeof(s1));
+}
--
Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/
Free Software Activist GNU Toolchain Engineer
More tolerance and less prejudice are key for inclusion and diversity
Excluding neuro-others for not behaving ""normal"" is *not* inclusive
