RISC-V: Introduce -mvector-strict-align.

this patch disables movmisalign by default and introduces
the -mno-vector-strict-align option to override it and re-enable
movmisalign.  For now, generic-ooo is the only uarch that supports
misaligned vector access.

The patch also adds a check_effective_target_riscv_v_misalign_ok to
the testsuite which enables or disables the vector misalignment tests
depending on whether the target under test can execute a misaligned
vle32.

Changes from v3:
 - Adressed Kito's comments.
 - Made -mscalar-strict-align a real alias.

gcc/ChangeLog:

	* config/riscv/riscv-opts.h (TARGET_VECTOR_MISALIGN_SUPPORTED):
	Move from here...
	* config/riscv/riscv.h (TARGET_VECTOR_MISALIGN_SUPPORTED):
	...to here and map to riscv_vector_unaligned_access_p.
	* config/riscv/riscv.opt: Add -mvector-strict-align.
	* config/riscv/riscv.cc (struct riscv_tune_param): Add
	vector_unaligned_access.
	(riscv_override_options_internal): Set
	riscv_vector_unaligned_access_p.
	* doc/invoke.texi: Document -mvector-strict-align.

gcc/testsuite/ChangeLog:

	* lib/target-supports.exp: Add
	check_effective_target_riscv_v_misalign_ok.
	* gcc.dg/vect/costmodel/riscv/rvv/dynamic-lmul2-7.c: Add
	-mno-vector-strict-align.
	* gcc.dg/vect/costmodel/riscv/rvv/vla_vs_vls-10.c: Ditto.
	* gcc.dg/vect/costmodel/riscv/rvv/vla_vs_vls-11.c: Ditto.
	* gcc.dg/vect/costmodel/riscv/rvv/vla_vs_vls-12.c: Ditto.
	* gcc.dg/vect/costmodel/riscv/rvv/vla_vs_vls-8.c: Ditto.
	* gcc.dg/vect/costmodel/riscv/rvv/vla_vs_vls-9.c: Ditto.
	* gcc.target/riscv/rvv/autovec/vls/misalign-1.c: Ditto.

1 files changed, 0 insertions, 3 deletions

diff --git a/gcc/config/riscv/riscv-opts.h b/gcc/config/riscv/riscv-opts.h
index 1b2dd57..f58a07a 100644
--- a/gcc/config/riscv/riscv-opts.h
+++ b/gcc/config/riscv/riscv-opts.h
@@ -147,9 +147,6 @@ enum rvv_vector_bits_enum {
      ? 0                                                                       \
      : 32 << (__builtin_popcount (opts->x_riscv_zvl_flags) - 1))
 
-/* TODO: Enable RVV movmisalign by default for now.  */
-#define TARGET_VECTOR_MISALIGN_SUPPORTED 1
-
 /* The maximmum LMUL according to user configuration.  */
 #define TARGET_MAX_LMUL                                                        \
   (int) (rvv_max_lmul == RVV_DYNAMIC ? RVV_M8 : rvv_max_lmul)