> -----Original Message-----
> From: wangjue <[email protected]>
> Sent: 10 September 2026 09:14
> To: [email protected]
> Cc: [email protected]; [email protected];
> [email protected]; [email protected]; juewang
> <[email protected]>
> Subject: [PATCH v2] vect: Look through promotions for SAT_TRUNC
>
> From: juewang <[email protected]>
>
> Use a single-use unpromoted input when MAX_EXPR and SAT_TRUNC are
> supported for the narrower type, avoiding a redundant widen-and-narrow
> sequence.
>
> The test cases were generated by an LLM.
>
> Assisted-by: GPT-6
>
> Regtested on rv64gcv, rv32gcv, x86_64 and aarch64 with no regressions.
>
> Changes since v1:
>
> v2: Update the test cases for the upstream canonicalization changes.
> v1: Add vect_sat_trunc_clip_input_vectype to check target support.
> Use the appropriate gimple_build_assign overload for MAX_EXPR.
>
Vect parts are OK. You need a RISCV maintainer for the tests.
Thanks,
Tamar
> gcc/ChangeLog:
>
> * tree-vect-patterns.cc (vect_sat_trunc_clip_input_vectype): New.
> (vect_recog_sat_trunc_pattern): Look through promotions and check
> target support for MAX_EXPR.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/riscv/rvv/autovec/pr120378-3.c: Disable the vector cost
> model.
> * gcc.target/riscv/rvv/autovec/pr120378-4.c: Likewise.
> * gcc.target/riscv/rvv/autovec/sat-trunc-promote-1.c: New test.
> * gcc.target/riscv/rvv/autovec/sat-trunc-promote-run-1.c: New test.
> ---
> .../gcc.target/riscv/rvv/autovec/pr120378-3.c | 2 +-
> .../gcc.target/riscv/rvv/autovec/pr120378-4.c | 2 +-
> .../riscv/rvv/autovec/sat-trunc-promote-1.c | 17 ++++
> .../rvv/autovec/sat-trunc-promote-run-1.c | 33 ++++++++
> gcc/tree-vect-patterns.cc | 83 +++++++++++++++----
> 5 files changed, 119 insertions(+), 18 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/autovec/sat-trunc-
> promote-1.c
> create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/autovec/sat-trunc-
> promote-run-1.c
>
> diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-3.c
> b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-3.c
> index 5941b3b7543..c06f1423140 100644
> --- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-3.c
> +++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-3.c
> @@ -1,5 +1,5 @@
> /* { dg-do compile } */
> -/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -fdump-tree-optimized" }
> */
> +/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -fno-vect-cost-model -
> fdump-tree-optimized" } */
>
> #include <stdint.h>
>
> diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-4.c
> b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-4.c
> index 57cca4504ba..bc9a55e8b07 100644
> --- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-4.c
> +++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr120378-4.c
> @@ -1,5 +1,5 @@
> /* { dg-do compile } */
> -/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -fdump-tree-optimized" }
> */
> +/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -fno-vect-cost-model -
> fdump-tree-optimized" } */
>
> #include <stdint.h>
>
> diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/sat-trunc-promote-1.c
> b/gcc/testsuite/gcc.target/riscv/rvv/autovec/sat-trunc-promote-1.c
> new file mode 100644
> index 00000000000..298a76461a4
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/sat-trunc-promote-1.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile } */
> +/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -mrvv-max-lmul=m1 -
> fno-vect-cost-model -fdump-tree-optimized" } */
> +
> +#include <stdint-gcc.h>
> +
> +__attribute__ ((noipa)) void
> +clip_scale_u8 (uint8_t *__restrict dst, const int8_t *__restrict src, int n)
> +{
> + for (int i = 0; i < n; ++i)
> + {
> + int x = src[i] * 3;
> + dst[i] = (unsigned) x > 255u ? (int) (-(unsigned) x) >> 31 : x;
> + }
> +}
> +
> +/* { dg-final { scan-tree-dump-times {\.SAT_TRUNC } 1 "optimized" } } */
> +/* { dg-final { scan-assembler-times {\tvnclipu\.wi} 1 } } */
> diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/sat-trunc-promote-run-
> 1.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/sat-trunc-promote-run-1.c
> new file mode 100644
> index 00000000000..04a7c09f07e
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/sat-trunc-promote-run-1.c
> @@ -0,0 +1,33 @@
> +/* { dg-do run { target { riscv_v && rv64 } } } */
> +/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -mrvv-max-lmul=m1 -
> fno-vect-cost-model" } */
> +
> +#include "sat-trunc-promote-1.c"
> +
> +#define N 256
> +
> +int
> +main (void)
> +{
> + int8_t input[N];
> + uint8_t output[N];
> +
> + for (int i = 0; i < N; ++i)
> + input[i] = i + INT8_MIN;
> +
> + /* Exercise every input value, empty loops and partial vectors. */
> + for (int n = 0; n <= N; ++n)
> + {
> + clip_scale_u8 (output, input, n);
> +
> +#pragma GCC novector
> + for (int i = 0; i < n; ++i)
> + {
> + int x = input[i] * 3;
> + uint8_t expected = x < 0 ? 0 : x > UINT8_MAX ? UINT8_MAX : x;
> + if (output[i] != expected)
> + __builtin_abort ();
> + }
> + }
> +
> + return 0;
> +}
> diff --git a/gcc/tree-vect-patterns.cc b/gcc/tree-vect-patterns.cc
> index 5fcc37f053c..06159fa6ab8 100644
> --- a/gcc/tree-vect-patterns.cc
> +++ b/gcc/tree-vect-patterns.cc
> @@ -4864,6 +4864,24 @@ vect_recog_sat_sub_pattern (vec_info *vinfo,
> stmt_vec_info stmt_vinfo,
> return NULL;
> }
>
> +/* Return the vector type for ITYPE if the target supports the MAX_EXPR
> + and SAT_TRUNC sequence. */
> +
> +static tree
> +vect_sat_trunc_clip_input_vectype (vec_info *vinfo, tree v_otype,
> + tree itype)
> +{
> + tree v_itype;
> + if (!vect_supportable_direct_optab_p
> + (vinfo, itype, MAX_EXPR, itype, &v_itype)
> + || !direct_internal_fn_supported_p
> + (IFN_SAT_TRUNC, tree_pair (v_otype, v_itype),
> + OPTIMIZE_FOR_BOTH))
> + return NULL_TREE;
> +
> + return v_itype;
> +}
> +
> /*
> * Try to detect saturation truncation pattern (SAT_TRUNC), aka below gimple:
> * overflow_5 = x_4(D) > 4294967295;
> @@ -4892,31 +4910,64 @@ vect_recog_sat_trunc_pattern (vec_info *vinfo,
> stmt_vec_info stmt_vinfo,
> if ((gimple_unsigned_integer_narrow_clip (lhs, ops, NULL))
> && type_has_mode_precision_p (otype))
> {
> - tree itype = TREE_TYPE (ops[0]);
> - tree v_itype = get_vectype_for_scalar_type (vinfo, itype);
> + tree input = ops[0];
> + tree itype = TREE_TYPE (input);
> tree v_otype = get_vectype_for_scalar_type (vinfo, otype);
> internal_fn fn = IFN_SAT_TRUNC;
> + tree v_itype = NULL_TREE;
>
> - if (v_itype != NULL_TREE && v_otype != NULL_TREE
> - && direct_internal_fn_supported_p (fn, tree_pair (v_otype, v_itype),
> - OPTIMIZE_FOR_BOTH))
> + if (v_otype != NULL_TREE)
> {
> - tree temp = vect_recog_temp_ssa_var (itype, NULL);
> - gimple * max_stmt = gimple_build_assign (temp, build2 (MAX_EXPR,
> itype, build_zero_cst(itype), ops[0]));
> - append_pattern_def_seq (vinfo, stmt_vinfo, max_stmt, v_itype);
> + /* Avoid widening an input only to narrow it again. A signed
> + promotion does not affect MAX (X, 0), so use the unpromoted
> + value when the target can narrow it directly to the output
> + type. */
> + vect_unpromoted_value unprom;
> + bool single_use_p = true;
> + if (vect_look_through_possible_promotion (vinfo, input, &unprom,
> + &single_use_p)
> + && single_use_p
> + && INTEGRAL_TYPE_P (unprom.type)
> + && TYPE_SIGN (unprom.type) == TYPE_SIGN (itype)
> + && type_has_mode_precision_p (unprom.type)
> + && TYPE_PRECISION (otype) < TYPE_PRECISION (unprom.type)
> + && TYPE_PRECISION (unprom.type) < TYPE_PRECISION (itype))
> + {
> + tree v_unprom_type
> + = vect_sat_trunc_clip_input_vectype (vinfo, v_otype,
> + unprom.type);
> + if (v_unprom_type != NULL_TREE)
> + {
> + input = unprom.op;
> + itype = unprom.type;
> + v_itype = v_unprom_type;
> + }
> + }
>
> - gcall *call = gimple_build_call_internal (fn, 1, temp);
> - tree out_ssa = vect_recog_temp_ssa_var (otype, NULL);
> + if (v_itype == NULL_TREE)
> + v_itype
> + = vect_sat_trunc_clip_input_vectype (vinfo, v_otype, itype);
>
> - gimple_call_set_lhs (call, out_ssa);
> - gimple_call_set_nothrow (call, /* nothrow_p */ false);
> - gimple_set_location (call, gimple_location (last_stmt));
> + if (v_itype != NULL_TREE)
> + {
> + tree temp = vect_recog_temp_ssa_var (itype, NULL);
> + gimple *max_stmt
> + = gimple_build_assign (temp, MAX_EXPR,
> + build_zero_cst (itype), input);
> + append_pattern_def_seq (vinfo, stmt_vinfo, max_stmt, v_itype);
>
> - *type_out = v_otype;
> + gcall *call = gimple_build_call_internal (fn, 1, temp);
> + tree out_ssa = vect_recog_temp_ssa_var (otype, NULL);
>
> - return call;
> - }
> + gimple_call_set_lhs (call, out_ssa);
> + gimple_call_set_nothrow (call, false);
> + gimple_set_location (call, gimple_location (last_stmt));
>
> + *type_out = v_otype;
> +
> + return call;
> + }
> + }
> }
>
> if ((gimple_unsigned_integer_sat_trunc (lhs, ops, NULL)
> --
> 2.34.1
