fold: Elide MASK_LEN_LOAD/STORE with zero length [PR122635].

This patch adds zero-length handling to gimple_fold_partial_store and
gimple_fold_partial_load and unifies them into
gimple_fold_partial_load_store.

It introduces a new function partial_load_store_mask_state that
returns
 MASK_ALL_INACTIVE,
 MASK_ALL_ACTIVE, or
 MASK_UNKNOWN.

This result is used to either replace a load with its else value and
elide a store (when all inactive), turn the load/store into a regular
mem ref (all_active), or do nothing.

	PR tree-optimization/122635

gcc/ChangeLog:

	* gimple-fold.cc (enum mask_load_store_state): New enum.
	(gimple_fold_partial_load_store_mem_ref): Only fold
	"all active" loads/stores.
	(partial_load_store_mask_state): New function to compute mask
	state.
	(gimple_fold_partial_load): Remove.
	(gimple_fold_partial_load_store): New function.
	(gimple_fold_partial_store): Remove.
	(gimple_fold_call): Use new function.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/sve/pfalse-store.c: Expect more elided
	stores.
	* gcc.target/riscv/rvv/autovec/pr122635-1.c: New test.
	* gcc.target/riscv/rvv/autovec/pr122635-2.c: New test.
	* gcc.target/powerpc/p9-vec-length-epil-8.c: Expect two lxvl
	less.

0 files changed, 0 insertions, 0 deletions