On Tue, 20 Jan 2026, liuhongt wrote:
> /* X86_TUNE_PREFER_BCST_FROM_INTEGER: Enable broadcast from integer for
> 128/256/512-bit vector, if disabled, the move will be done by
> broadcast/load from constant pool
>
> broadcast from integer:
> mov $0xa,%eax
> vmovd %eax,%xmm0
> vpbroadcastd %xmm0,%xmm0
>
> broadcast/load from constant pool:
> vpbroadcastd CST.0(%rip), %xmm0 */
>
> The tune is on by default.
Thanks!
I wonder if the broadcast/load from constnat pool could be late
split in to the former when a GPR is available (and the tune
indicates it's profitable).
> gcc/ChangeLog:
>
> PR target/123631
> * config/i386/i386-expand.cc (ix86_vector_duplicate_value):
> Don't force CONST_INT to reg !TARGET_PREFER_BCST_FROM_INTEGER,
> force it to mem instead.
> * config/i386/i386.h (TARGET_PREFER_BCST_FROM_INTEGER): New macro.
> * config/i386/x86-tune.def
> (X86_TUNE_PREFER_BCST_FROM_INTEGER): New tune.
> ---
> gcc/config/i386/i386-expand.cc | 17 +++++++++++++----
> gcc/config/i386/i386.h | 3 +++
> gcc/config/i386/x86-tune.def | 15 +++++++++++++++
> 3 files changed, 31 insertions(+), 4 deletions(-)
>
> diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
> index d6525ddcdd0..a82bb4399c9 100644
> --- a/gcc/config/i386/i386-expand.cc
> +++ b/gcc/config/i386/i386-expand.cc
> @@ -17361,12 +17361,21 @@ ix86_vector_duplicate_value (machine_mode mode, rtx
> target, rtx val)
> machine_mode innermode = GET_MODE_INNER (mode);
> rtx reg;
>
> - /* If that fails, force VAL into a register. */
> + /* If that fails, force VAL into a register or mem. */
>
> start_sequence ();
> - reg = force_reg (innermode, val);
> - if (GET_MODE (reg) != innermode)
> - reg = gen_lowpart (innermode, reg);
> +
> + if (!TARGET_PREFER_BCST_FROM_INTEGER && CONST_INT_P (val)
> + && GET_MODE_BITSIZE (innermode) <= HOST_BITS_PER_WIDE_INT
> + && GET_MODE_BITSIZE(mode) >= 128)
> + reg = validize_mem (force_const_mem (innermode, val));
> + else
> + {
> + reg = force_reg (innermode, val);
> + if (GET_MODE (reg) != innermode)
> + reg = gen_lowpart (innermode, reg);
> + }
> +
> SET_SRC (PATTERN (insn)) = gen_vec_duplicate (mode, reg);
> seq = end_sequence ();
> if (seq)
> diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
> index 71bacc22052..888edfed88f 100644
> --- a/gcc/config/i386/i386.h
> +++ b/gcc/config/i386/i386.h
> @@ -409,6 +409,9 @@ extern unsigned char ix86_tune_features[X86_TUNE_LAST];
> ix86_tune_features[X86_TUNE_INTER_UNIT_MOVES_FROM_VEC]
> #define TARGET_INTER_UNIT_CONVERSIONS \
> ix86_tune_features[X86_TUNE_INTER_UNIT_CONVERSIONS]
> +#define TARGET_PREFER_BCST_FROM_INTEGER \
> + ix86_tune_features[X86_TUNE_PREFER_BCST_FROM_INTEGER]
> +
> #define TARGET_FOUR_JUMP_LIMIT
> ix86_tune_features[X86_TUNE_FOUR_JUMP_LIMIT]
> #define TARGET_SCHEDULE ix86_tune_features[X86_TUNE_SCHEDULE]
> #define TARGET_USE_BT ix86_tune_features[X86_TUNE_USE_BT]
> diff --git a/gcc/config/i386/x86-tune.def b/gcc/config/i386/x86-tune.def
> index a1944620daf..53cf1a19433 100644
> --- a/gcc/config/i386/x86-tune.def
> +++ b/gcc/config/i386/x86-tune.def
> @@ -488,6 +488,21 @@ DEF_TUNE (X86_TUNE_INTER_UNIT_MOVES_FROM_VEC,
> "inter_unit_moves_from_vec",
> DEF_TUNE (X86_TUNE_INTER_UNIT_CONVERSIONS, "inter_unit_conversions",
> ~(m_AMDFAM10 | m_BDVER))
>
> +/* X86_TUNE_PREFER_BCST_FROM_INTEGER: Enable broadcast from integer for
> + 128/256/512-bit vector, if disabled, the move will be done by
> + broadcast/load from constant pool
> +
> + broadcast from integer:
> + mov $0xa,%eax
> + vmovd %eax,%xmm0
> + vpbroadcastd %xmm0,%xmm0
> +
> + broadcast/load from constant pool:
> + vpbroadcastd CST.0(%rip), %xmm0 */
> +
> +DEF_TUNE (X86_TUNE_PREFER_BCST_FROM_INTEGER, "prefer_bcst_from_integer",
> + m_ALL)
> +
> /* X86_TUNE_SPLIT_MEM_OPND_FOR_FP_CONVERTS: Try to split memory operand for
> fp converts to destination register. */
> DEF_TUNE (X86_TUNE_SPLIT_MEM_OPND_FOR_FP_CONVERTS,
> "split_mem_opnd_for_fp_converts",
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
