LoongArch: Improve reassociation for bitwise operation and left shift [PR 115921]

For things like

        (x | 0x101) << 11

It's obvious to write:

        ori     $r4,$r4,257
        slli.d  $r4,$r4,11

But we are actually generating something insane:

        lu12i.w $r12,524288>>12             # 0x80000
        ori     $r12,$r12,2048
        slli.d  $r4,$r4,11
        or      $r4,$r4,$r12
        jr      $r1

It's because the target-independent canonicalization was written before
we have all the RISC targets where loading an immediate may need
multiple instructions.  So for these targets we need to handle this in
the target code.

We do the reassociation on our own (i.e. reverting the
target-independent reassociation) if "(reg [&|^] mask) << shamt" does
not need to load mask into an register, and either:
- (mask << shamt) needs to be loaded into an register, or
- shamt is a const_immalsl_operand, so the outer shift may be further
  combined with an add.

gcc/ChangeLog:

	PR target/115921
	* config/loongarch/loongarch-protos.h
	(loongarch_reassoc_shift_bitwise): New function prototype.
	* config/loongarch/loongarch.cc
	(loongarch_reassoc_shift_bitwise): Implement.
	* config/loongarch/loongarch.md
	(*alslsi3_extend_subreg): New define_insn_and_split.
	(<any_bitwise:optab>_shift_reverse<X:mode>): New
	define_insn_and_split.
	(<any_bitwise:optab>_alsl_reversesi_extended): New
	define_insn_and_split.
	(zero_extend_ashift): Remove as it's just a special case of
	and_shift_reversedi, and it does not make too much sense to
	write "alsl.d rd,rs,r0,shamt" instead of "slli.d rd,rs,shamt".
	(bstrpick_alsl_paired): Remove as it is already done by
	splitting and_shift_reversedi into and + ashift first, then
	late combining the ashift and a further add.

gcc/testsuite/ChangeLog:

	PR target/115921
	* gcc.target/loongarch/bstrpick_alsl_paired.c (scan-rtl-dump):
	Scan for and_shift_reversedi instead of the removed
	bstrpick_alsl_paired.
	* gcc.target/loongarch/bitwise-shift-reassoc.c: New test.

0 files changed, 0 insertions, 0 deletions