Compiling simple shader for iOS on Windows - runtime error on iPhone Simulator "Shader Compilation Failed"

[neildanson]

I've been playing with a simple shader, and wanted to move the code to run on iOS:

The Effect file looks like this

# if OPENGL

#define SV_POSITION POSITION
#define VS_SHADERMODEL vs_3_0
#define PS_SHADERMODEL ps_3_0

# else


#define VS_SHADERMODEL vs_4_0_level_9_1
#define PS_SHADERMODEL ps_4_0_level_9_1

# endif

matrix WorldViewProjection;

struct VertexShaderInput
{
    float4 Position : SV_POSITION;
    float3 Normal : NORMAL0;
    float3 Color : COLOR0;
};

struct VertexShaderOutput
{
    float4 Position : SV_POSITION;
    float3 Normal : NORMAL;
    float4 Color : COLOR0;
};

VertexShaderOutput MainVS(in VertexShaderInput input)
{
    VertexShaderOutput output = (VertexShaderOutput)0;

    output.Position = mul(input.Position, WorldViewProjection);
    output.Color = float4(input.Color,1);
    output.Normal = input.Normal; 
    return output;
}

float4 MainPS(VertexShaderOutput input) : COLOR
{
    return input.Color \* saturate(dot(float3(-0.5,0.3,-0.5), input.Normal));
}

technique BasicColorDrawing
{
    pass P0
    {
        VertexShader = compile VS_SHADERMODEL MainVS();
        PixelShader = compile PS_SHADERMODEL MainPS();
    }
};

And when run through the MonoGame Content Pipeline on Win10 (selecting build iOS) the xnb looks like this

XNBi
precision mediump float;
precision mediump int;
# endif

const vec4 ps_c0 = vec4(-0.5, 0.3, 0.0, 0.0);
vec4 ps_r0;
# define ps_oC0 gl_FragColor

varying vec4 vFrontColor;
# define ps_v1 vFrontColor

void main()
{
    ps_r0.x = clamp(dot(ps_c0.xyx, ps_v0.xyz), 0.0, 1.0);
    ps_oC0 = ps_r0.xxxx \* ps_v1;
}

precision highp float;
precision mediump int;
# endif

uniform vec4 vs_uniforms_vec4[4];
uniform vec4 posFixup;
const vec4 vs_c4 = vec4(1.0, 0.0, 0.0, 0.0);
# define vs_c0 vs_uniforms_vec4[0]
# define vs_c1 vs_uniforms_vec4[1]
# define vs_c2 vs_uniforms_vec4[2]
# define vs_c3 vs_uniforms_vec4[3]

attribute vec4 vs_v0;
# define vs_o0 gl_Position

attribute vec4 vs_v1;
vec4 vs_o1;
attribute vec4 vs_v2;
varying vec4 vFrontColor;
# define vs_o2 vFrontColor

void main()
{
    vs_o0.x = dot(vs_v0, vs_c0);
    vs_o0.y = dot(vs_v0, vs_c1);
    vs_o0.z = dot(vs_v0, vs_c2);
    vs_o0.w = dot(vs_v0, vs_c3);
    vs_o1.xyz = vs_v1.xyz;
    vs_o2 = (vs_v2.xyzx \* vs_c4.xxxy) + vs_c4.yyyx;
    gl_Position.y = gl_Position.y \* posFixup.y;
    gl_Position.xy += posFixup.zw \* gl_Position.ww;
    gl_Position.z = gl_Position.z \* 2.0 - gl_Position.w;
}

The XNB loads fine, but on calling DrawIndexedPrimitive I get an exception stating the "Shader Compilation Failed"

Monogame 3.5.1.1679 on both OSes.

If there is anything extra you need me to add, please let me know.

[neildanson]

Attached source and XNB file in a zip

Effect.zip

[neildanson]

Update:

I fixed the issue by changing the effect to do all the lighting in the vertex shader.

While my specific issue is fixed, I still think the behaviour is wrong - I'd expect either the compile step to fail in the pipeline, or to fail to load, rather failing at the point of trying to use the shader.