[3/77] Allow machine modes to be classes

[3/77] Allow machine modes to be classes

This patch makes various changes that allow modes like SImode to be
classes rather than enums.

Firstly, it adds inline functions for all mode size properties,
with the macros being simple wrappers around them.  This is necessary
for the __builtin_constant_p trick to continue working effectively when
the mode arguments are slightly more complex (but still foldable at
compile time).

These inline functions are trivial and heavily used.  There's not much
point keeping them out-of-line at -O0: if anything it would make
debugging harder rather than easier, and it would also slow things down.
The patch therefore marks them as "always_inline", if that's available.
Later patches use this approach too.

Using inline functions means that it's no longer possible to pass
an int to GET_MODE_PRECISION etc.  The Fortran and powerpcspe-c.c
parts are needed to avoid instances of that.

The patch continues to use enums for gencondmd.c, so that more
mode comparisons are integer constant expressions when checking
for always-true or always-false conditions.  This is the only
intended use of USE_ENUM_MODES.

The patch also enforces the previous replacement of case statements
by defining modes as:

  #define FOOmode ((void) 0, E_FOOmode)

This adds no overhead but makes sure that new uses of "case FOOmode:"
don't accidentally creep in when FOOmode has no specific class associated
with it.

2017-08-30  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* genconditions.c (write_header): Add a "#define USE_ENUM_MODES".
	* genmodes.c (emit_insn_modes_h): Define FOOmode to E_FOOmode if
	USE_ENUM_MODES is defined and to ((void) 0, E_FOOmode) otherwise.
	* machmode.h (mode_size): Move earlier in file.
	(mode_precision): Likewise.
	(mode_inner): Likewise.
	(mode_nunits): Likewise.
	(mode_unit_size): Likewise.
	(unit_unit_precision): Likewise.
	(mode_wider): Likewise.
	(mode_2xwider): Likewise.
	(machine_mode): New class.
	(mode_to_bytes): New function.
	(mode_to_bits): Likewise.
	(mode_to_precision): Likewise.
	(mode_to_inner): Likewise.
	(mode_to_unit_size): Likewise.
	(mode_to_unit_precision): Likewise.
	(mode_to_nunits): Likewise.
	(GET_MODE_SIZE): Use mode_to_bytes.
	(GET_MODE_BITSIZE): Use mode_to_bits.
	(GET_MODE_PRECISION): Use mode_to_precision.
	(GET_MODE_INNER): Use mode_to_inner.
	(GET_MODE_UNIT_SIZE): Use mode_to_unit_size.
	(GET_MODE_UNIT_PRECISION): Use mode_to_unit_precision.
	(GET_MODE_NUNITS): Use mode_to_nunits.
	* system.h (ALWAYS_INLINE): New macro.
	* config/powerpcspe/powerpcspe-c.c
	(altivec_resolve_overloaded_builtin): Use machine_mode instead of
	int for arg1_mode and arg2_mode.

gcc/fortran/
	* trans-types.c (gfc_init_kinds): Use machine_mode instead of int
	for "mode".

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@251454 138bc75d-0d04-0410-961f-82ee72b054a4