double LSKeyframeAnimationFunctionEaseInOutQuart(double t, double b, double c,
                                                 double d) {
  if ((t /= d / 2) < 1)
    return c / 2 * t * t * t * t + b;
  return -c / 2 * ((t -= 2) * t * t * t - 2) + b;
}


x86 assembly (clang, -O0):
<LSKeyframeAnimationFunctionEaseInOutQuart>:
push   %rbp
mov    %rsp,%rbp
movsd  %xmm0,-0x10(%rbp)
movsd  %xmm1,-0x18(%rbp)
movsd  %xmm2,-0x20(%rbp)
movsd  %xmm3,-0x28(%rbp)
movsd  -0x28(%rbp),%xmm0
movsd  0xee3(%rip),%xmm1
divsd  %xmm1,%xmm0
movsd  -0x10(%rbp),%xmm1
divsd  %xmm0,%xmm1
movsd  %xmm1,-0x10(%rbp)
movsd  0xec1(%rip),%xmm0
ucomisd %xmm1,%xmm0
jbe    1185 <LSKeyframeAnimationFunctionEaseInOutQuart+0x85>
movsd  -0x20(%rbp),%xmm0
movsd  0xeb2(%rip),%xmm1
divsd  %xmm1,%xmm0
mulsd  -0x10(%rbp),%xmm0
mulsd  -0x10(%rbp),%xmm0
mulsd  -0x10(%rbp),%xmm0
movsd  -0x10(%rbp),%xmm2
movsd  -0x18(%rbp),%xmm1
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
movsd  %xmm0,-0x8(%rbp)
jmp    11f4 <LSKeyframeAnimationFunctionEaseInOutQuart+0xf4>
movsd  -0x20(%rbp),%xmm0
movq   %xmm0,%rax
movabs $0x8000000000000000,%rcx
xor    %rcx,%rax
movq   %rax,%xmm0
movsd  0xe5f(%rip),%xmm1
divsd  %xmm1,%xmm0
movsd  -0x10(%rbp),%xmm2
movsd  0xe4e(%rip),%xmm1
subsd  %xmm1,%xmm2
movsd  %xmm2,-0x10(%rbp)
mulsd  -0x10(%rbp),%xmm2
mulsd  -0x10(%rbp),%xmm2
movsd  -0x10(%rbp),%xmm1
mulsd  %xmm1,%xmm2
movsd  0xe32(%rip),%xmm1
addsd  %xmm1,%xmm2
movsd  -0x18(%rbp),%xmm1
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
movsd  %xmm0,-0x8(%rbp)
movsd  -0x8(%rbp),%xmm0
pop    %rbp
ret

x86 assembly (clang, -O2):
<LSKeyframeAnimationFunctionEaseInOutQuart>:
mulsd  0xef8(%rip),%xmm3
divsd  %xmm3,%xmm0
movsd  0xef4(%rip),%xmm3
ucomisd %xmm0,%xmm3
jbe    113b <LSKeyframeAnimationFunctionEaseInOutQuart+0x3b>
mulsd  0xede(%rip),%xmm2
mulsd  %xmm0,%xmm2
mulsd  %xmm0,%xmm2
mulsd  %xmm0,%xmm2
mulsd  %xmm0,%xmm2
addsd  %xmm1,%xmm2
movapd %xmm2,%xmm0
ret
mulsd  0xecd(%rip),%xmm2
movsd  0xecd(%rip),%xmm4
addsd  %xmm4,%xmm0
movapd %xmm0,%xmm3
mulsd  %xmm0,%xmm3
mulsd  %xmm0,%xmm3
mulsd  %xmm0,%xmm3
addsd  %xmm4,%xmm3
mulsd  %xmm2,%xmm3
addsd  %xmm1,%xmm3
movapd %xmm3,%xmm0
ret

LLVM IR (-O0):
define double @LSKeyframeAnimationFunctionEaseInOutQuart(double %0, double %1, double %2, double %3) {
%5 = alloca double
%6 = alloca double
%7 = alloca double
%8 = alloca double
%9 = alloca double
store double %0, double* %6
store double %1, double* %7
store double %2, double* %8
store double %3, double* %9
%10 = load double, double* %9
%11 = fdiv double %10, 2.000000e+00
%12 = load double, double* %6
%13 = fdiv double %12, %11
store double %13, double* %6
%14 = fcmp olt double %13, 1.000000e+00
br i1 %14, label %15, label %27
15: ; preds = %4
%16 = load double, double* %8
%17 = fdiv double %16, 2.000000e+00
%18 = load double, double* %6
%19 = fmul double %17, %18
%20 = load double, double* %6
%21 = fmul double %19, %20
%22 = load double, double* %6
%23 = fmul double %21, %22
%24 = load double, double* %6
%25 = load double, double* %7
%26 = call double @llvm.fmuladd.f64(double %23, double %24, double %25)
store double %26, double* %5
br label %41
27: ; preds = %4
%28 = load double, double* %8
%29 = fneg double %28
%30 = fdiv double %29, 2.000000e+00
%31 = load double, double* %6
%32 = fsub double %31, 2.000000e+00
store double %32, double* %6
%33 = load double, double* %6
%34 = fmul double %32, %33
%35 = load double, double* %6
%36 = fmul double %34, %35
%37 = load double, double* %6
%38 = call double @llvm.fmuladd.f64(double %36, double %37, double -2.000000e+00)
%39 = load double, double* %7
%40 = call double @llvm.fmuladd.f64(double %30, double %38, double %39)
store double %40, double* %5
br label %41
41: ; preds = %27, %15
%42 = load double, double* %5
ret double %42
}

LLVM IR (-O2):
define double @LSKeyframeAnimationFunctionEaseInOutQuart(double %0, double %1, double %2, double %3) {
%5 = fmul double %3, 5.000000e-01
%6 = fdiv double %0, %5
%7 = fcmp olt double %6, 1.000000e+00
br i1 %7, label %8, label %14
8: ; preds = %4
%9 = fmul double %2, 5.000000e-01
%10 = fmul double %9, %6
%11 = fmul double %6, %10
%12 = fmul double %6, %11
%13 = tail call double @llvm.fmuladd.f64(double %12, double %6, double %1)
br label %21
14: ; preds = %4
%15 = fmul double %2, -5.000000e-01
%16 = fadd double %6, -2.000000e+00
%17 = fmul double %16, %16
%18 = fmul double %16, %17
%19 = tail call double @llvm.fmuladd.f64(double %18, double %16, double -2.000000e+00)
%20 = tail call double @llvm.fmuladd.f64(double %15, double %19, double %1)
br label %21
21: ; preds = %14, %8
%22 = phi double [ %13, %8 ], [ %20, %14 ]
ret double %22
}