user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/options/internal/riscv64/fenv.S

@@ -0,0 +1,57 @@
+
+#ifdef __riscv_flen
+
+.global feclearexcept
+.type feclearexcept, %function
+feclearexcept:
+	csrc fflags, a0
+	li a0, 0
+	ret
+
+.global feraiseexcept
+.type feraiseexcept, %function
+feraiseexcept:
+	csrs fflags, a0
+	li a0, 0
+	ret
+
+.global fetestexcept
+.type fetestexcept, %function
+fetestexcept:
+	frflags t0
+	and a0, t0, a0
+	ret
+
+.global fegetround
+.type fegetround, %function
+fegetround:
+	frrm a0
+	ret
+
+.global __fesetround
+.type __fesetround, %function
+__fesetround:
+	fsrm t0, a0
+	li a0, 0
+	ret
+
+.global fegetenv
+.type fegetenv, %function
+fegetenv:
+	frcsr t0
+	sw t0, 0(a0)
+	li a0, 0
+	ret
+
+.global fesetenv
+.type fesetenv, %function
+fesetenv:
+	li t2, -1
+	li t1, 0
+	beq a0, t2, 1f
+	lw t1, 0(a0)
+1:	fscsr t1
+	li a0, 0
+	ret
+
+#endif