xtensa: constantsynth: Update to version 2

xtensa: constantsynth: Update to version 2

This patch completely replaces the existing "constantsynth" with a new
implementation, which has become unsightly due to the extension.

This new version offers the following benefits:

  - Independence from the insn splitting mechanism.  No define_split
    descriptions are required
  - Resource saving as internally required information storage no longer
    persists across passes
  - The replacement of insns is based on the actual costs (for both size
    and speed) of the insns before and after the conversion, rather than
    on some arbitrary pre-determined ones
  - The replacing insn sequence is verified by formally evaluating the
    RTL expressions to see if it correctly computes the original constant
    value
  - Easy-to-understand/-add interface for constant synthesis methods

The built-in synthesis methods are (supposedly) very effective, with 2
instructions for certain values and up to 5 instructions to cover all
32-bit values.

     /* example */
     _Complex double test(int a[], float b[]) {
       a[0] = 2045 * 2045;
       a[1] = 0xDEADBEEF;
       a[2] = 0xDEADBEEF - 15;
       a[3] = 4182000;
       a[4] = 131071;
       a[5] = 293805;
       a[6] = 700972933;
       a[7] = -372738139;
       b[0] = 3.14159265359f;
       b[1] *= 0.12005615234375f;
       return 1-1i;
     }

     ;; result (-O2 -mextra-l32r-costs=5)
     test:
     	entry	sp, 32
     	movi	a8, 0x7af
     	float.s	f1, a8, 14
     	movi	a8, 0x7fd
     	mull	a8, a8, a8
     	lsi	f0, a3, 4
     	s32i.n	a8, a2, 0
     	movi.n	a8, 0x57
     	addmi	a8, a8, -0x1100
     	slli	a8, a8, 17
     	addmi	a8, a8, -0x4100
     	addi	a8, a8, -17
     	s32i.n	a8, a2, 4
     	addi	a8, a8, -15
     	s32i.n	a8, a2, 8
     	movi	a8, 0x3fd
     	slli	a8, a8, 12
     	addi	a8, a8, -16
     	s32i.n	a8, a2, 12
     	movi.n	a8, -1
     	srli	a8, a8, 15
     	s32i.n	a8, a2, 16
     	movi	a8, 0x85
     	addmi	a8, a8, 0x7f00
     	addx8	a8, a8, a8
     	s32i.n	a8, a2, 20
     	movi	a8, 0x539
     	slli	a8, a8, 19
     	addi	a8, a8, -123
     	s32i.n	a8, a2, 24
     	movi	a8, -0x2c7
     	slli	a8, a8, 19
     	addmi	a8, a8, 0x7800
     	addi	a8, a8, -91
     	s32i.n	a8, a2, 28
     	movi.n	a8, 0x49
     	mul.s	f0, f0, f1
     	addmi	a8, a8, 0x4000
     	slli	a8, a8, 16
     	addmi	a8, a8, 0x1000
     	addi	a8, a8, -37
     	s32i.n	a8, a3, 0
     	ssi	f0, a3, 4
     	movi	a5, -0x401
     	movi	a3, 0x3ff
     	movi.n	a2, 0
     	slli	a3, a3, 20
     	movi.n	a4, 0
     	slli	a5, a5, 20
     	retw.n

gcc/ChangeLog:

	* config/xtensa/xtensa-protos.h (xtensa_constantsynth): Remove.
	* config/xtensa/xtensa.cc
	(#include): Remove "context.h" and "pass_manager.h".
	(machine_function): Remove "litpool_usage" member.
	(xtensa_constantsynth_2insn, xtensa_constantsynth_rtx_SLLI,
	xtensa_constantsynth_rtx_ADDSUBX, xtensa_constantsynth): Remove.
	(constantsynth_method_lshr_m1, split_hwi_to_MOVI_ADDMI,
	constantsynth_method_16bits, constantsynth_method_32bits,
	constantsynth_method_square): New worker function related to
	constant synthesis methods.
	(constantsynth_method_info, constantsynth_methods):
	New structure representing the list of all constant synthesis
	methods.
	(constantsynth_info): New structure that stores internal
	information for "constantsynth".
	(constantsynth_pass1, verify_synth_seq, constantsynth_pass2):
	New functions that are the core of "constantsynth".
	(do_largeconst): Add a call to constantsynth_pass1() to the insn
	enumeration loop, and add a call to constantsynth_pass2() to the
	end of this function.
	* config/xtensa/xtensa.md (SHI): Remove.
	(The two auxiliary define_splits for mov[sh]i_internal): Remove.
	(The two auxiliary define_splits for movsf_internal): Remove.

gcc/testsuite/ChangeLog:

	* gcc.target/xtensa/constsynth_2insns.c,
	gcc.target/xtensa/constsynth_3insns.c,
	gcc.target/xtensa/constsynth_double.c: Remove due to outdated.
	* gcc.target/xtensa/constsynthV2_O2_costs0.c,
	gcc.target/xtensa/constsynthV2_O2_costs5.c,
	gcc.target/xtensa/constsynthV2_Os.c: New.