[PATCH 6/7] RISC-V: Make vectorized memset handle more cases

[Jeff Law]

On 10/18/24 7:12 AM, Craig Blackmore wrote:
> `expand_vec_setmem` only generated vectorized memset if it fitted into a
> single vector store.  Extend it to generate a loop for longer and
> unknown lengths.
> 
> The test cases now use -O1 so that they are not sensitive to scheduling.
> 
> gcc/ChangeLog:
> 
> 	* config/riscv/riscv-string.cc
> 	(use_vector_stringop_p): Add comment.
> 	(expand_vec_setmem): Use use_vector_stringop_p instead of
> 	check_vectorise_memory_operation.  Add loop generation.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* gcc.target/riscv/rvv/base/setmem-1.c: Use -O1.  Expect a loop
> 	instead of a libcall.  Add test for unknown length.
> 	* gcc.target/riscv/rvv/base/setmem-2.c: Likewise.
> 	* gcc.target/riscv/rvv/base/setmem-3.c: Likewise and expect smaller
> 	lmul.
So why handle memset differently than the other mem* routines where we 
limit ourselves to what we can handle without needing loops?

My suspicion is that once we're moving enough data that we can't do it 
with a single big lmul store that calling out to the library variant 
probably isn't a big deal for memset.  Do you have data which suggests 
otherwise?

Jeff