I saw many redundant scalar modes:

 E_CDImode,               /* machmode.def:267 */
#define HAVE_CDImode
#ifdef USE_ENUM_MODES
#define CDImode E_CDImode
#else
#define CDImode (complex_mode ((complex_mode::from_int) E_CDImode))
#endif
  E_CTImode,               /* machmode.def:267 */
#define HAVE_CTImode
#ifdef USE_ENUM_MODES
#define CTImode E_CTImode
#else
#define CTImode (complex_mode ((complex_mode::from_int) E_CTImode))
#endif
  E_HCmode,                /* machmode.def:269 */
#define HAVE_HCmode
#ifdef USE_ENUM_MODES
#define HCmode E_HCmode
#else
#define HCmode (complex_mode ((complex_mode::from_int) E_HCmode))
#endif
  E_SCmode,                /* machmode.def:269 */
#define HAVE_SCmode
#ifdef USE_ENUM_MODES
#define SCmode E_SCmode
#else
#define SCmode (complex_mode ((complex_mode::from_int) E_SCmode))
#endif
  E_DCmode,                /* machmode.def:269 */
#define HAVE_DCmode
#ifdef USE_ENUM_MODES
#define DCmode E_DCmode
#else
#define DCmode (complex_mode ((complex_mode::from_int) E_DCmode))
#endif
  E_TCmode,                /* machmode.def:269 */
#define HAVE_TCmode
#ifdef USE_ENUM_MODES
#define TCmode E_TCmode
#else
#define TCmode (complex_mode ((complex_mode::from_int) E_TCmode))
#endif
...

These scalar modes are redundant I think, can we forbid them?
There are 40+ scalar modes that are not used.



juzhe.zhong@rivai.ai
 
From: juzhe.zhong@rivai.ai
Date: 2023-04-10 23:22
To: jakub; Jeff Law
CC: gcc-patches; kito.cheng; palmer; richard.sandiford; rguenther
Subject: Re: Re: [PATCH] machine_mode type size: Extend enum size from 8-bit to 16-bit
Yeah, aarch64 already has 178, RVV has much more types than aarch64...
You can see intrinsic doc:
https://github.com/riscv-non-isa/rvv-intrinsic-doc/blob/eopc/tuple-type-for-seg-load-store/auto-generated/intrinsic_funcs/02_vector_unit-stride_segment_load_store_instructions_zvlsseg.md 
api number explodes.

As well as tuples types in RVV much more than aarch64.
Maybe we need to ask RVV api doc maintainer to reduce types && api of RVV?
Not sure.
I think kito may help for this.


juzhe.zhong@rivai.ai
 
From: Jakub Jelinek
Date: 2023-04-10 23:18
To: Jeff Law
CC: juzhe.zhong; gcc-patches; kito.cheng; palmer; richard.sandiford; rguenther
Subject: Re: [PATCH] machine_mode type size: Extend enum size from 8-bit to 16-bit
On Mon, Apr 10, 2023 at 08:54:12AM -0600, Jeff Law wrote:
> This is likely going to be very controversial.  It's going to increase the
> size of two of most heavily used data structures in GCC (rtx and trees).
> 
> The first thing I would ask is whether or not we really need the full matrix
> in practice or if we can combine some of the modes.
> 
> Why hasn't aarch64 stumbled over this problem?
 
From what I can see, x86 has 130 modes and aarch64 178 right now.
 
Jakub