double LSKeyframeAnimationFunctionEaseInOutBack(double t, double b, double c,
                                                double d) {
  double s = 1.70158;
  if ((t /= d / 2) < 1)
    return c / 2 * (t * t * (((s *= (1.525)) + 1) * t - s)) + b;
  return c / 2 * ((t -= 2) * t * (((s *= (1.525)) + 1) * t + s) + 2) + b;
}


x86 assembly (clang, -O0):
<LSKeyframeAnimationFunctionEaseInOutBack>:
push   %rbp
mov    %rsp,%rbp
movsd  %xmm0,-0x10(%rbp)
movsd  %xmm1,-0x18(%rbp)
movsd  %xmm2,-0x20(%rbp)
movsd  %xmm3,-0x28(%rbp)
movsd  0xef0(%rip),%xmm0
movsd  %xmm0,-0x30(%rbp)
movsd  -0x28(%rbp),%xmm0
movsd  0xed6(%rip),%xmm1
divsd  %xmm1,%xmm0
movsd  -0x10(%rbp),%xmm1
divsd  %xmm0,%xmm1
movsd  %xmm1,-0x10(%rbp)
movsd  0xeb4(%rip),%xmm0
ucomisd %xmm1,%xmm0
jbe    11d3 <LSKeyframeAnimationFunctionEaseInOutBack+0xd3>
movsd  -0x20(%rbp),%xmm0
movsd  0xea5(%rip),%xmm1
divsd  %xmm1,%xmm0
movsd  -0x10(%rbp),%xmm2
mulsd  -0x10(%rbp),%xmm2
movsd  0xe9f(%rip),%xmm1
mulsd  -0x30(%rbp),%xmm1
movsd  %xmm1,-0x30(%rbp)
movsd  0xe75(%rip),%xmm3
addsd  %xmm3,%xmm1
movsd  -0x10(%rbp),%xmm4
movsd  -0x30(%rbp),%xmm3
movq   %xmm3,%rax
movabs $0x8000000000000000,%rcx
xor    %rcx,%rax
movq   %rax,%xmm3
mulsd  %xmm4,%xmm1
addsd  %xmm3,%xmm1
mulsd  %xmm1,%xmm2
movsd  -0x18(%rbp),%xmm1
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
movsd  %xmm0,-0x8(%rbp)
jmp    1251 <LSKeyframeAnimationFunctionEaseInOutBack+0x151>
movsd  -0x20(%rbp),%xmm0
movsd  0xe28(%rip),%xmm1
divsd  %xmm1,%xmm0
movsd  -0x10(%rbp),%xmm2
movsd  0xe17(%rip),%xmm1
subsd  %xmm1,%xmm2
movsd  %xmm2,-0x10(%rbp)
mulsd  -0x10(%rbp),%xmm2
movsd  0xe11(%rip),%xmm1
mulsd  -0x30(%rbp),%xmm1
movsd  %xmm1,-0x30(%rbp)
movsd  0xde7(%rip),%xmm3
addsd  %xmm3,%xmm1
movsd  -0x10(%rbp),%xmm4
movsd  -0x30(%rbp),%xmm3
mulsd  %xmm4,%xmm1
addsd  %xmm3,%xmm1
mulsd  %xmm1,%xmm2
movsd  0xdcd(%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):
<LSKeyframeAnimationFunctionEaseInOutBack>:
mulsd  0xef8(%rip),%xmm3
divsd  %xmm3,%xmm0
movsd  0xef4(%rip),%xmm3
ucomisd %xmm0,%xmm3
jbe    1138 <LSKeyframeAnimationFunctionEaseInOutBack+0x38>
movapd %xmm0,%xmm3
mulsd  0xef2(%rip),%xmm0
mulsd  %xmm3,%xmm3
addsd  0xefe(%rip),%xmm0
mulsd  %xmm3,%xmm0
jmp    1164 <LSKeyframeAnimationFunctionEaseInOutBack+0x64>
addsd  0xed0(%rip),%xmm0
movapd %xmm0,%xmm3
mulsd  0xecc(%rip),%xmm0
addsd  0xecc(%rip),%xmm0
mulsd  %xmm3,%xmm3
mulsd  %xmm3,%xmm0
addsd  0xec4(%rip),%xmm0
mulsd  0xe94(%rip),%xmm2
mulsd  %xmm0,%xmm2
addsd  %xmm1,%xmm2
movapd %xmm2,%xmm0
ret

LLVM IR (-O0):
define double @LSKeyframeAnimationFunctionEaseInOutBack(double %0, double %1, double %2, double %3) {
%5 = alloca double
%6 = alloca double
%7 = alloca double
%8 = alloca double
%9 = alloca double
%10 = alloca double
store double %0, double* %6
store double %1, double* %7
store double %2, double* %8
store double %3, double* %9
store double 1.701580e+00, double* %10
%11 = load double, double* %9
%12 = fdiv double %11, 2.000000e+00
%13 = load double, double* %6
%14 = fdiv double %13, %12
store double %14, double* %6
%15 = fcmp olt double %14, 1.000000e+00
br i1 %15, label %16, label %32
16: ; preds = %4
%17 = load double, double* %8
%18 = fdiv double %17, 2.000000e+00
%19 = load double, double* %6
%20 = load double, double* %6
%21 = fmul double %19, %20
%22 = load double, double* %10
%23 = fmul double %22, 1.525000e+00
store double %23, double* %10
%24 = fadd double %23, 1.000000e+00
%25 = load double, double* %6
%26 = load double, double* %10
%27 = fneg double %26
%28 = call double @llvm.fmuladd.f64(double %24, double %25, double %27)
%29 = fmul double %21, %28
%30 = load double, double* %7
%31 = call double @llvm.fmuladd.f64(double %18, double %29, double %30)
store double %31, double* %5
br label %48
32: ; preds = %4
%33 = load double, double* %8
%34 = fdiv double %33, 2.000000e+00
%35 = load double, double* %6
%36 = fsub double %35, 2.000000e+00
store double %36, double* %6
%37 = load double, double* %6
%38 = fmul double %36, %37
%39 = load double, double* %10
%40 = fmul double %39, 1.525000e+00
store double %40, double* %10
%41 = fadd double %40, 1.000000e+00
%42 = load double, double* %6
%43 = load double, double* %10
%44 = call double @llvm.fmuladd.f64(double %41, double %42, double %43)
%45 = call double @llvm.fmuladd.f64(double %38, double %44, double 2.000000e+00)
%46 = load double, double* %7
%47 = call double @llvm.fmuladd.f64(double %34, double %45, double %46)
store double %47, double* %5
br label %48
48: ; preds = %32, %16
%49 = load double, double* %5
ret double %49
}

LLVM IR (-O2):
define double @LSKeyframeAnimationFunctionEaseInOutBack(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 %12
8: ; preds = %4
%9 = fmul double %6, %6
%10 = tail call double @llvm.fmuladd.f64(double %6, double 0x400CC25FE974A340, double 0xC004C25FE974A340)
%11 = fmul double %9, %10
br label %17
12: ; preds = %4
%13 = fadd double %6, -2.000000e+00
%14 = fmul double %13, %13
%15 = tail call double @llvm.fmuladd.f64(double %13, double 0x400CC25FE974A340, double 0x4004C25FE974A340)
%16 = tail call double @llvm.fmuladd.f64(double %14, double %15, double 2.000000e+00)
br label %17
17: ; preds = %12, %8
%18 = phi double [ %16, %12 ], [ %11, %8 ]
%19 = fmul double %2, 5.000000e-01
%20 = tail call double @llvm.fmuladd.f64(double %19, double %18, double %1)
ret double %20
}