void one_step_euler(y, dt, yp, neq, t) double dt, *t;
double *y, *yp;
int neq;
{
  int j;
  set_wieners(dt, y, *t);
  rhs(*t, y, yp, neq);
  *t += dt;
  for (j = 0; j < neq; j++)
    y[j] = y[j] + dt * yp[j];
}


x86 assembly (clang, -O0):
<one_step_euler>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
mov    %rdi,-0x8(%rbp)
movsd  %xmm0,-0x10(%rbp)
mov    %rsi,-0x18(%rbp)
mov    %edx,-0x1c(%rbp)
mov    %rcx,-0x28(%rbp)
movsd  -0x10(%rbp),%xmm0
mov    -0x8(%rbp),%rdi
mov    -0x28(%rbp),%rax
movsd  (%rax),%xmm1
mov    $0x2,%al
call   1040 <set_wieners@plt>
mov    -0x28(%rbp),%rax
movsd  (%rax),%xmm0
mov    -0x8(%rbp),%rdi
mov    -0x18(%rbp),%rsi
mov    -0x1c(%rbp),%edx
mov    $0x1,%al
call   1030 <rhs@plt>
movsd  -0x10(%rbp),%xmm0
mov    -0x28(%rbp),%rax
addsd  (%rax),%xmm0
movsd  %xmm0,(%rax)
movl   $0x0,-0x2c(%rbp)
mov    -0x2c(%rbp),%eax
cmp    -0x1c(%rbp),%eax
jge    11d4 <one_step_euler+0xb4>
mov    -0x8(%rbp),%rax
movslq -0x2c(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm1
movsd  -0x10(%rbp),%xmm0
mov    -0x18(%rbp),%rax
movslq -0x2c(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm2
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x8(%rbp),%rax
movslq -0x2c(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
mov    -0x2c(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x2c(%rbp)
jmp    1186 <one_step_euler+0x66>
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<one_step_euler>:
push   %rbp
push   %r15
push   %r14
push   %rbx
sub    $0x18,%rsp
mov    %rcx,%rbp
mov    %edx,%r15d
mov    %rsi,%r14
movaps %xmm0,(%rsp)
mov    %rdi,%rbx
movsd  (%rcx),%xmm1
mov    $0x2,%al
call   1040 <set_wieners@plt>
movsd  0x0(%rbp),%xmm0
mov    %rbx,%rdi
mov    %r14,%rsi
mov    %r15d,%edx
mov    $0x1,%al
call   1030 <rhs@plt>
movapd (%rsp),%xmm6
movsd  0x0(%rbp),%xmm0
addsd  %xmm6,%xmm0
movsd  %xmm0,0x0(%rbp)
test   %r15d,%r15d
jle    12e5 <one_step_euler+0x1c5>
mov    %r15d,%eax
cmp    $0x4,%r15d
jb     1191 <one_step_euler+0x71>
lea    (%r14,%rax,8),%rcx
cmp    %rbx,%rcx
jbe    11f9 <one_step_euler+0xd9>
lea    (%rbx,%rax,8),%rcx
cmp    %r14,%rcx
jbe    11f9 <one_step_euler+0xd9>
xor    %ecx,%ecx
mov    %rcx,%rdx
not    %rdx
test   $0x1,%al
je     11b5 <one_step_euler+0x95>
movsd  (%r14,%rcx,8),%xmm0
mulsd  %xmm6,%xmm0
addsd  (%rbx,%rcx,8),%xmm0
movsd  %xmm0,(%rbx,%rcx,8)
or     $0x1,%rcx
add    %rax,%rdx
je     12e5 <one_step_euler+0x1c5>
xchg   %ax,%ax
movsd  (%r14,%rcx,8),%xmm0
mulsd  %xmm6,%xmm0
addsd  (%rbx,%rcx,8),%xmm0
movsd  %xmm0,(%rbx,%rcx,8)
movsd  0x8(%r14,%rcx,8),%xmm0
mulsd  %xmm6,%xmm0
addsd  0x8(%rbx,%rcx,8),%xmm0
movsd  %xmm0,0x8(%rbx,%rcx,8)
add    $0x2,%rcx
cmp    %rcx,%rax
jne    11c0 <one_step_euler+0xa0>
jmp    12e5 <one_step_euler+0x1c5>
mov    %eax,%ecx
and    $0xfffffffc,%ecx
movapd %xmm6,%xmm0
unpcklpd %xmm6,%xmm0
lea    -0x4(%rcx),%rdx
mov    %rdx,%rsi
shr    $0x2,%rsi
add    $0x1,%rsi
test   %rdx,%rdx
je     12f0 <one_step_euler+0x1d0>
mov    %rsi,%rdi
and    $0xfffffffffffffffe,%rdi
xor    %edx,%edx
nopw   0x0(%rax,%rax,1)
movupd (%r14,%rdx,8),%xmm1
movupd 0x10(%r14,%rdx,8),%xmm2
mulpd  %xmm0,%xmm1
movupd (%rbx,%rdx,8),%xmm3
addpd  %xmm1,%xmm3
movupd 0x10(%rbx,%rdx,8),%xmm1
movupd 0x20(%rbx,%rdx,8),%xmm4
movupd 0x30(%rbx,%rdx,8),%xmm5
mulpd  %xmm0,%xmm2
addpd  %xmm1,%xmm2
movupd %xmm3,(%rbx,%rdx,8)
movupd %xmm2,0x10(%rbx,%rdx,8)
movupd 0x20(%r14,%rdx,8),%xmm1
movupd 0x30(%r14,%rdx,8),%xmm2
mulpd  %xmm0,%xmm1
addpd  %xmm4,%xmm1
mulpd  %xmm0,%xmm2
addpd  %xmm5,%xmm2
movupd %xmm1,0x20(%rbx,%rdx,8)
movupd %xmm2,0x30(%rbx,%rdx,8)
add    $0x8,%rdx
add    $0xfffffffffffffffe,%rdi
jne    1230 <one_step_euler+0x110>
test   $0x1,%sil
je     12dc <one_step_euler+0x1bc>
movupd (%rbx,%rdx,8),%xmm1
movupd 0x10(%rbx,%rdx,8),%xmm2
movupd (%r14,%rdx,8),%xmm3
movupd 0x10(%r14,%rdx,8),%xmm4
mulpd  %xmm0,%xmm3
addpd  %xmm1,%xmm3
mulpd  %xmm0,%xmm4
addpd  %xmm2,%xmm4
movupd %xmm3,(%rbx,%rdx,8)
movupd %xmm4,0x10(%rbx,%rdx,8)
cmp    %rax,%rcx
jne    1193 <one_step_euler+0x73>
add    $0x18,%rsp
pop    %rbx
pop    %r14
pop    %r15
pop    %rbp
ret
xor    %edx,%edx
test   $0x1,%sil
jne    12a9 <one_step_euler+0x189>
jmp    12dc <one_step_euler+0x1bc>

LLVM IR (-O0):
define void @one_step_euler(double* %0, double %1, double* %2, i32 %3, double* %4) {
%6 = alloca double*
%7 = alloca double
%8 = alloca double*
%9 = alloca i32
%10 = alloca double*
%11 = alloca i32
store double* %0, double** %6
store double %1, double* %7
store double* %2, double** %8
store i32 %3, i32* %9
store double* %4, double** %10
%12 = load double, double* %7
%13 = load double*, double** %6
%14 = load double*, double** %10
%15 = load double, double* %14
%16 = call i32 (double, double*, double, ...) bitcast (i32 (...)* @set_wieners to i32 (double, double*, double, ...)*)(double %12, double* %13, double %15)
%17 = load double*, double** %10
%18 = load double, double* %17
%19 = load double*, double** %6
%20 = load double*, double** %8
%21 = load i32, i32* %9
%22 = call i32 (double, double*, double*, i32, ...) bitcast (i32 (...)* @rhs to i32 (double, double*, double*, i32, ...)*)(double %18, double* %19, double* %20, i32 %21)
%23 = load double, double* %7
%24 = load double*, double** %10
%25 = load double, double* %24
%26 = fadd double %25, %23
store double %26, double* %24
store i32 0, i32* %11
br label %27
27: ; preds = %48, %5
%28 = load i32, i32* %11
%29 = load i32, i32* %9
%30 = icmp slt i32 %28, %29
br i1 %30, label %31, label %51
31: ; preds = %27
%32 = load double*, double** %6
%33 = load i32, i32* %11
%34 = sext i32 %33 to i64
%35 = getelementptr inbounds double, double* %32, i64 %34
%36 = load double, double* %35
%37 = load double, double* %7
%38 = load double*, double** %8
%39 = load i32, i32* %11
%40 = sext i32 %39 to i64
%41 = getelementptr inbounds double, double* %38, i64 %40
%42 = load double, double* %41
%43 = call double @llvm.fmuladd.f64(double %37, double %42, double %36)
%44 = load double*, double** %6
%45 = load i32, i32* %11
%46 = sext i32 %45 to i64
%47 = getelementptr inbounds double, double* %44, i64 %46
store double %43, double* %47
br label %48
48: ; preds = %31
%49 = load i32, i32* %11
%50 = add nsw i32 %49, 1
store i32 %50, i32* %11
br label %27
51: ; preds = %27
ret void
}

LLVM IR (-O2):
define void @one_step_euler(double* %0, double %1, double* %2, i32 %3, double* nocapture %4) {
%6 = load double, double* %4
%7 = tail call i32 (double, double*, double, ...) bitcast (i32 (...)* @set_wieners to i32 (double, double*, double, ...)*)(double %1, double* %0, double %6)
%8 = load double, double* %4
%9 = tail call i32 (double, double*, double*, i32, ...) bitcast (i32 (...)* @rhs to i32 (double, double*, double*, i32, ...)*)(double %8, double* %0, double* %2, i32 %3)
%10 = load double, double* %4
%11 = fadd double %10, %1
store double %11, double* %4
%12 = icmp sgt i32 %3, 0
br i1 %12, label %13, label %127
13: ; preds = %5
%14 = zext i32 %3 to i64
%15 = icmp ult i32 %3, 4
br i1 %15, label %96, label %16
16: ; preds = %13
%17 = getelementptr double, double* %0, i64 %14
%18 = getelementptr double, double* %2, i64 %14
%19 = icmp ugt double* %18, %0
%20 = icmp ugt double* %17, %2
%21 = and i1 %19, %20
br i1 %21, label %96, label %22
22: ; preds = %16
%23 = and i64 %14, 4294967292
%24 = insertelement <2 x double> poison, double %1, i64 0
%25 = shufflevector <2 x double> %24, <2 x double> poison, <2 x i32> zeroinitializer
%26 = insertelement <2 x double> poison, double %1, i64 0
%27 = shufflevector <2 x double> %26, <2 x double> poison, <2 x i32> zeroinitializer
%28 = add nsw i64 %23, -4
%29 = lshr exact i64 %28, 2
%30 = add nuw nsw i64 %29, 1
%31 = and i64 %30, 1
%32 = icmp eq i64 %28, 0
br i1 %32, label %74, label %33
33: ; preds = %22
%34 = and i64 %30, 9223372036854775806
br label %35
35: ; preds = %35, %33
%36 = phi i64 [ 0, %33 ], [ %71, %35 ]
%37 = phi i64 [ 0, %33 ], [ %72, %35 ]
%38 = getelementptr inbounds double, double* %0, i64 %36
%39 = bitcast double* %38 to <2 x double>*
%40 = load <2 x double>, <2 x double>* %39
%41 = getelementptr inbounds double, double* %38, i64 2
%42 = bitcast double* %41 to <2 x double>*
%43 = load <2 x double>, <2 x double>* %42
%44 = getelementptr inbounds double, double* %2, i64 %36
%45 = bitcast double* %44 to <2 x double>*
%46 = load <2 x double>, <2 x double>* %45
%47 = getelementptr inbounds double, double* %44, i64 2
%48 = bitcast double* %47 to <2 x double>*
%49 = load <2 x double>, <2 x double>* %48
%50 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %25, <2 x double> %46, <2 x double> %40)
%51 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %27, <2 x double> %49, <2 x double> %43)
%52 = bitcast double* %38 to <2 x double>*
store <2 x double> %50, <2 x double>* %52
%53 = bitcast double* %41 to <2 x double>*
store <2 x double> %51, <2 x double>* %53
%54 = or i64 %36, 4
%55 = getelementptr inbounds double, double* %0, i64 %54
%56 = bitcast double* %55 to <2 x double>*
%57 = load <2 x double>, <2 x double>* %56
%58 = getelementptr inbounds double, double* %55, i64 2
%59 = bitcast double* %58 to <2 x double>*
%60 = load <2 x double>, <2 x double>* %59
%61 = getelementptr inbounds double, double* %2, i64 %54
%62 = bitcast double* %61 to <2 x double>*
%63 = load <2 x double>, <2 x double>* %62
%64 = getelementptr inbounds double, double* %61, i64 2
%65 = bitcast double* %64 to <2 x double>*
%66 = load <2 x double>, <2 x double>* %65
%67 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %25, <2 x double> %63, <2 x double> %57)
%68 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %27, <2 x double> %66, <2 x double> %60)
%69 = bitcast double* %55 to <2 x double>*
store <2 x double> %67, <2 x double>* %69
%70 = bitcast double* %58 to <2 x double>*
store <2 x double> %68, <2 x double>* %70
%71 = add nuw i64 %36, 8
%72 = add i64 %37, 2
%73 = icmp eq i64 %72, %34
br i1 %73, label %74, label %35
74: ; preds = %35, %22
%75 = phi i64 [ 0, %22 ], [ %71, %35 ]
%76 = icmp eq i64 %31, 0
br i1 %76, label %94, label %77
77: ; preds = %74
%78 = getelementptr inbounds double, double* %0, i64 %75
%79 = bitcast double* %78 to <2 x double>*
%80 = load <2 x double>, <2 x double>* %79
%81 = getelementptr inbounds double, double* %78, i64 2
%82 = bitcast double* %81 to <2 x double>*
%83 = load <2 x double>, <2 x double>* %82
%84 = getelementptr inbounds double, double* %2, i64 %75
%85 = bitcast double* %84 to <2 x double>*
%86 = load <2 x double>, <2 x double>* %85
%87 = getelementptr inbounds double, double* %84, i64 2
%88 = bitcast double* %87 to <2 x double>*
%89 = load <2 x double>, <2 x double>* %88
%90 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %25, <2 x double> %86, <2 x double> %80)
%91 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %27, <2 x double> %89, <2 x double> %83)
%92 = bitcast double* %78 to <2 x double>*
store <2 x double> %90, <2 x double>* %92
%93 = bitcast double* %81 to <2 x double>*
store <2 x double> %91, <2 x double>* %93
br label %94
94: ; preds = %74, %77
%95 = icmp eq i64 %23, %14
br i1 %95, label %127, label %96
96: ; preds = %16, %13, %94
%97 = phi i64 [ 0, %16 ], [ 0, %13 ], [ %23, %94 ]
%98 = xor i64 %97, -1
%99 = and i64 %14, 1
%100 = icmp eq i64 %99, 0
br i1 %100, label %108, label %101
101: ; preds = %96
%102 = getelementptr inbounds double, double* %0, i64 %97
%103 = load double, double* %102
%104 = getelementptr inbounds double, double* %2, i64 %97
%105 = load double, double* %104
%106 = tail call double @llvm.fmuladd.f64(double %1, double %105, double %103)
store double %106, double* %102
%107 = or i64 %97, 1
br label %108
108: ; preds = %101, %96
%109 = phi i64 [ %97, %96 ], [ %107, %101 ]
%110 = sub nsw i64 0, %14
%111 = icmp eq i64 %98, %110
br i1 %111, label %127, label %112
112: ; preds = %108, %112
%113 = phi i64 [ %125, %112 ], [ %109, %108 ]
%114 = getelementptr inbounds double, double* %0, i64 %113
%115 = load double, double* %114
%116 = getelementptr inbounds double, double* %2, i64 %113
%117 = load double, double* %116
%118 = tail call double @llvm.fmuladd.f64(double %1, double %117, double %115)
store double %118, double* %114
%119 = add nuw nsw i64 %113, 1
%120 = getelementptr inbounds double, double* %0, i64 %119
%121 = load double, double* %120
%122 = getelementptr inbounds double, double* %2, i64 %119
%123 = load double, double* %122
%124 = tail call double @llvm.fmuladd.f64(double %1, double %123, double %121)
store double %124, double* %120
%125 = add nuw nsw i64 %113, 2
%126 = icmp eq i64 %125, %14
br i1 %126, label %127, label %112
127: ; preds = %108, %112, %94, %5
ret void
}