vect: Allow unsigned-to-signed promotion in vect_look_through_possible_promotion [PR115707]
Checks
Commit Message
The function vect_look_through_possible_promotion() fails to figure out root
definition if casts involves more than two promotions with sign change as:
long a = (long)b; // promotion cast
-> int b = (int)c; // promotion cast, sign change
-> unsigned short c = ...;
For this case, the function thinks the 2nd cast has different sign as the 1st,
so stop looking through, while "unsigned short -> integer" is a nature sign
extension. This patch allows this unsigned-to-signed promotion in the function.
Thanks,
Feng
---
gcc/
* tree-vect-patterns.cc (vect_look_through_possible_promotion): Allow
unsigned-to-signed promotion.
---
gcc/tree-vect-patterns.cc | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
Comments
On Mon, Aug 5, 2024 at 12:34 PM Feng Xue OS <fxue@os.amperecomputing.com> wrote:
>
> The function vect_look_through_possible_promotion() fails to figure out root
> definition if casts involves more than two promotions with sign change as:
>
> long a = (long)b; // promotion cast
> -> int b = (int)c; // promotion cast, sign change
> -> unsigned short c = ...;
>
> For this case, the function thinks the 2nd cast has different sign as the 1st,
> so stop looking through, while "unsigned short -> integer" is a nature sign
> extension. This patch allows this unsigned-to-signed promotion in the function.
OK.
Thanks,
Richard.
> Thanks,
> Feng
>
> ---
> gcc/
> * tree-vect-patterns.cc (vect_look_through_possible_promotion): Allow
> unsigned-to-signed promotion.
> ---
> gcc/tree-vect-patterns.cc | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/tree-vect-patterns.cc b/gcc/tree-vect-patterns.cc
> index 4674a16d15f..b2c83cfd219 100644
> --- a/gcc/tree-vect-patterns.cc
> +++ b/gcc/tree-vect-patterns.cc
> @@ -434,7 +434,9 @@ vect_look_through_possible_promotion (vec_info *vinfo, tree op,
> sign of the previous promotion. */
> if (!res
> || TYPE_PRECISION (unprom->type) == orig_precision
> - || TYPE_SIGN (unprom->type) == TYPE_SIGN (op_type))
> + || TYPE_SIGN (unprom->type) == TYPE_SIGN (op_type)
> + || (TYPE_UNSIGNED (op_type)
> + && TYPE_PRECISION (op_type) < TYPE_PRECISION (unprom->type)))
> {
> unprom->set_op (op, dt, caster);
> min_precision = TYPE_PRECISION (op_type);
> --
> 2.17.1
From 334998e1d991e1d2c8e4c2234663b4d829e88e5c Mon Sep 17 00:00:00 2001
From: Feng Xue <fxue@os.amperecomputing.com>
Date: Mon, 5 Aug 2024 15:23:56 +0800
Subject: [PATCH] vect: Allow unsigned-to-signed promotion in
vect_look_through_possible_promotion [PR115707]
The function fails to figure out root definition if casts involves more than
two promotions with sign change as:
long a = (long)b; // promotion cast
-> int b = (int)c; // promotion cast, sign change
-> unsigned short c = ...;
For this case, the function thinks the 2nd cast has different sign as the 1st,
so stop looking through, while "unsigned short -> integer" is a nature sign
extension.
2024-08-05 Feng Xue <fxue@os.amperecomputing.com>
gcc/
* tree-vect-patterns.cc (vect_look_through_possible_promotion): Allow
unsigned-to-signed promotion.
---
gcc/tree-vect-patterns.cc | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
@@ -434,7 +434,9 @@ vect_look_through_possible_promotion (vec_info *vinfo, tree op,
sign of the previous promotion. */
if (!res
|| TYPE_PRECISION (unprom->type) == orig_precision
- || TYPE_SIGN (unprom->type) == TYPE_SIGN (op_type))
+ || TYPE_SIGN (unprom->type) == TYPE_SIGN (op_type)
+ || (TYPE_UNSIGNED (op_type)
+ && TYPE_PRECISION (op_type) < TYPE_PRECISION (unprom->type)))
{
unprom->set_op (op, dt, caster);
min_precision = TYPE_PRECISION (op_type);
--
2.17.1