loongarch: add alternatives for idiv insns to improve code generation

Currently in the description of LoongArch integer division instructions,
the output is marked as earlyclobbered ('&').  It's necessary when
loongarch_check_zero_div_p() because clobbering operand 2 (divisor) will
make the checking for zero divisor impossible.

But, for -mno-check-zero-division (the default of GCC >= 12.2 for
optimized code), the output is not earlyclobbered at all.  And, the
read of operand 1 only occurs before clobbering the output.  So we make
three alternatives for an idiv instruction:

* (=r,r,r): For -mno-check-zero-division.
* (=&r,r,r): For -mcheck-zero-division.
* (=&r,0,r): For -mcheck-zero-division, to explicitly allow patterns
  like "div.d $a0, $a0, $a1".

gcc/ChangeLog:

	* config/loongarch/loongarch.cc (loongarch_check_zero_div_p):
	Remove static, for use in the machine description file.
	* config/loongarch/loongarch-protos.h:
	(loongarch_check_zero_div_p): Add prototype.
	* config/loongarch/loongarch.md (enabled): New attr.
	(*<optab><mode>3): Add (=r,r,r) and (=&r,0,r) alternatives for
	idiv.  Conditionally enable the alternatives using
	loongarch_check_zero_div_p.
	(<optab>di3_fake): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.target/loongarch/div-1.c: New test.
	* gcc.target/loongarch/div-2.c: New test.
	* gcc.target/loongarch/div-3.c: New test.

0 files changed, 0 insertions, 0 deletions