?

\[0 \leq x \land x \leq 0.5\]

\[\cos^{-1} \left(1 - x\right) \]

(FPCore (x) :precision binary64 (acos (- 1.0 x)))

double code(double x) {
	return acos((1.0 - x));
}

real(8) function code(x)
    real(8), intent (in) :: x
    code = acos((1.0d0 - x))
end function

public static double code(double x) {
	return Math.acos((1.0 - x));
}

def code(x):
	return math.acos((1.0 - x))

function code(x)
	return acos(Float64(1.0 - x))
end

function tmp = code(x)
	tmp = acos((1.0 - x));
end

code[x_] := N[ArcCos[N[(1.0 - x), $MachinePrecision]], $MachinePrecision]

\cos^{-1} \left(1 - x\right)

Reproduce?

Please include this information when filing a bug report:

herbie shell --seed 2023241 
(FPCore (x)
  :name "bug323 (missed optimization)"
  :precision binary64
  :pre (and (<= 0.0 x) (<= x 0.5))

  :herbie-target
  (* 2.0 (asin (sqrt (/ x 2.0))))

  (acos (- 1.0 x)))

Backtrace

match: no matching clause for 'ival		L	C
compile-progs	/home/nightlies/herbie/arb-support/src/programs.rkt	122	0
make-search-func	/home/nightlies/herbie/arb-support/src/ground-truth.rkt	20	0
sample-points	/home/nightlies/herbie/arb-support/src/ground-truth.rkt	64	0
setup-context!	/home/nightlies/herbie/arb-support/src/mainloop.rkt	293	0
get-alternatives/report	/home/nightlies/herbie/arb-support/src/sandbox.rkt	148	0
(unnamed)	/home/nightlies/herbie/arb-support/src/sandbox.rkt	247	6
(unnamed)	/usr/share/racket/pkgs/profile-lib/main.rkt	40	10
profile-thunk	/usr/share/racket/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/usr/share/racket/collects/racket/engine.rkt	42	24