[committed][RISC-V] Fix 20010221-1.c with zicond

[committed][RISC-V] Fix 20010221-1.c with zicond

So we're being a bit too aggressive with the .opt zicond patterns.

> (define_insn "*czero.eqz.<GPR:mode><X:mode>.opt1"
>   [(set (match_operand:GPR 0 "register_operand"                   "=r")
>         (if_then_else:GPR (eq (match_operand:X 1 "register_operand" "r")
>                               (const_int 0))
>                           (match_operand:GPR 2 "register_operand" "1")
>                           (match_operand:GPR 3 "register_operand" "r")))]
>   "(TARGET_ZICOND || 1) && rtx_equal_p (operands[1], operands[2])"
>   "czero.eqz\t%0,%3,%1"
> )
The RTL semantics here are op0 = (op1 == 0) ? op1 : op2.  That maps
directly to czero.eqz.  ie, we select op1 when we know it's zero, op2
otherwise.  So this pattern is fine.

> (define_insn "*czero.eqz.<GPR:mode><X:mode>.opt2"
>   [(set (match_operand:GPR 0 "register_operand"                   "=r")
>         (if_then_else:GPR (eq (match_operand:X 1 "register_operand" "r")
>                               (const_int 0))
>                           (match_operand:GPR 2 "register_operand" "r")
>                           (match_operand:GPR 3 "register_operand" "1")))]
>   "(TARGET_ZICOND || 1) && rtx_equal_p (operands[1],  operands[3])"
>   "czero.nez\t%0,%2,%1"
> )

The RTL semantics of this pattern are are: op0 = (op1 == 0) ? op2 : op1;

That's not something that can be expressed by the zicond extension as it
selects op1 if and only if op1 is not equal to zero.

> (define_insn "*czero.nez.<GPR:mode><X:mode>.opt3"
>   [(set (match_operand:GPR 0 "register_operand"                   "=r")
>         (if_then_else:GPR (ne (match_operand:X 1 "register_operand" "r")
>                               (const_int 0))
>                           (match_operand:GPR 2 "register_operand" "r")
>                           (match_operand:GPR 3 "register_operand" "1")))]
>   "(TARGET_ZICOND || 1) && rtx_equal_p (operands[1], operands[3])"
>   "czero.eqz\t%0,%2,%1"
> )
The RTL semantics of this pattern are op0 = (op1 != 0) ? op2 : op1.
That maps to czero.nez.  But the output template uses czero.eqz.  Opps.

> (define_insn "*czero.nez.<GPR:mode><X:mode>.opt4"
>   [(set (match_operand:GPR 0 "register_operand"                   "=r")
>         (if_then_else:GPR (ne (match_operand:X 1 "register_operand" "r")
>                               (const_int 0))
>                           (match_operand:GPR 2 "register_operand" "1")
>                           (match_operand:GPR 3 "register_operand" "r")))]
>   "(TARGET_ZICOND || 1) && rtx_equal_p (operands[1], operands[2])"
>   "czero.nez\t%0,%3,%1"
> )

The RTL semantics of this pattern are op0 = (op1 != 0) ? op1 : op2 which
obviously doesn't match to any zicond instruction as op1 is selected
when it is not zero.

So two of the patterns are just totally bogus as they are not
implementable with zicond.  They are removed.  The asm template for the
.opt3 pattern is fixed to use czero.nez and its name is changed to
.opt2.

gcc/
	* config/riscv/zicond.md: Remove incorrect zicond patterns and
	renumber/rename them.
	(zero.nez.<GPR:MODE><X:mode>.opt2): Fix output string.