Make more use of int_mode_for_size

Make more use of int_mode_for_size

This patch converts more places that could use int_mode_for_size instead
of mode_for_size.  This is in preparation for an upcoming patch that
makes mode_for_size itself return an opt_mode.

require () seems like the right choice in expand_builtin_powi
because we have got past the point of backing out.  We go on to do:

  op1 = expand_expr (arg1, NULL_RTX, mode2, EXPAND_NORMAL);
  if (GET_MODE (op1) != mode2)
    op1 = convert_to_mode (mode2, op1, 0);

which would be invalid for (and have failed for) BLKmode.

In get_builtin_sync_mode and expand_ifn_atomic_compare_exchange,
the possible bitsizes are {8, 16, 32, 64, 128}, all of which give
target-independent integer modes (up to TImode).  The comment above
the call in get_builtin_sync_mode makes clear that an integer mode
must be found.

We can use require () in expand_builtin_atomic_clear and
expand_builtin_atomic_test_and_set because there's always an integer
mode for the boolean type.  The same goes for the POINTER_SIZE request
in layout_type.  Similarly we can use require () in combine_instructions
and gen_lowpart_common because there's always an integer mode for
HOST_BITS_PER_WIDE_INT (DImode when BITS_PER_UNIT == 8), and
HOST_BITS_PER_DOUBLE_INT (TImode).

The calls in aarch64_function_value, arm_function_value,
aapcs_allocate_return_reg and mips_function_value_1 are handling
cases in which a big-endian target passes or returns values at
the most significant end of a register.  In each case the ABI
constrains the size to a small amount and does not handle
non-power-of-2 sizes wider than a word.

The calls in c6x_expand_movmem, i386.c:emit_memset,
lm32_block_move_inline, microblaze_block_move_straight and
mips_block_move_straight are dealing with expansions of
block memory operations using register-wise operations,
and those registers must have non-BLK mode.

The reason for using require () in ix86_expand_sse_cmp,
mips_expand_ins_as_unaligned_store, spu.c:adjust_operand and
spu_emit_branch_and_set is that we go on to emit non-call
instructions that use registers of that mode, which wouldn't
be valid for BLKmode.

2017-09-05  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* builtins.c (expand_builtin_powi): Use int_mode_for_size.
	(get_builtin_sync_mode): Likewise.
	(expand_ifn_atomic_compare_exchange): Likewise.
	(expand_builtin_atomic_clear): Likewise.
	(expand_builtin_atomic_test_and_set): Likewise.
	(fold_builtin_atomic_always_lock_free): Likewise.
	* calls.c (compute_argument_addresses): Likewise.
	(emit_library_call_value_1): Likewise.
	(store_one_arg): Likewise.
	* combine.c (combine_instructions): Likewise.
	* config/aarch64/aarch64.c (aarch64_function_value): Likewise.
	* config/arm/arm.c (arm_function_value): Likewise.
	(aapcs_allocate_return_reg): Likewise.
	* config/c6x/c6x.c (c6x_expand_movmem): Likewise.
	* config/i386/i386.c (construct_container): Likewise.
	(ix86_gimplify_va_arg): Likewise.
	(ix86_expand_sse_cmp): Likewise.
	(emit_memmov): Likewise.
	(emit_memset): Likewise.
	(expand_small_movmem_or_setmem): Likewise.
	(ix86_expand_pextr): Likewise.
	(ix86_expand_pinsr): Likewise.
	* config/lm32/lm32.c (lm32_block_move_inline): Likewise.
	* config/microblaze/microblaze.c (microblaze_block_move_straight):
	Likewise.
	* config/mips/mips.c (mips_function_value_1) Likewise.
	(mips_block_move_straight): Likewise.
	(mips_expand_ins_as_unaligned_store): Likewise.
	* config/powerpcspe/powerpcspe.c
	(rs6000_darwin64_record_arg_advance_flush): Likewise.
	(rs6000_darwin64_record_arg_flush): Likewise.
	* config/rs6000/rs6000.c
	(rs6000_darwin64_record_arg_advance_flush): Likewise.
	(rs6000_darwin64_record_arg_flush): Likewise.
	* config/sparc/sparc.c (sparc_function_arg_1): Likewise.
	(sparc_function_value_1): Likewise.
	* config/spu/spu.c (adjust_operand): Likewise.
	(spu_emit_branch_or_set): Likewise.
	(arith_immediate_p): Likewise.
	* emit-rtl.c (gen_lowpart_common): Likewise.
	* expr.c (expand_expr_real_1): Likewise.
	* function.c (assign_parm_setup_block): Likewise.
	* gimple-ssa-store-merging.c (encode_tree_to_bitpos): Likewise.
	* reload1.c (alter_reg): Likewise.
	* stor-layout.c (mode_for_vector): Likewise.
	(layout_type): Likewise.

gcc/ada/
	* gcc-interface/utils2.c (build_load_modify_store):
	Use int_mode_for_size.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@251726 138bc75d-0d04-0410-961f-82ee72b054a4