[Bug 101378] interpolateAtSample check for input parameter is too strict

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101378

            Bug ID: 101378
           Summary: interpolateAtSample check for input parameter is too
                    strict
           Product: Mesa
           Version: 17.0
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: glsl-compiler
          Assignee: mesa-dev at lists.freedesktop.org
          Reporter: freedesktop at ca.sh13.net
        QA Contact: intel-3d-bugs at lists.freedesktop.org

The following code snippet fails on Mesa 17.0.3 with the following error:

    in GeometryToPixel
    {
        vec3 color;
        vec2 uv;
    } gs2ps;

   out vec4 Color;

   void main ()
   {
        Color = vec4(gs2ps.color, 1);

        if (length(interpolateAtSample(gs2ps.uv, gl_SampleID))>1) {
                discard;
        }
    }

This is the error:

    0:10(1): error: if a fragment input is (or contains) an integer, then it
must be qualified with 'flat'
    0:10(8): error: `gl_SampleID' redeclared
    0:18(33): error: parameter `interpolant` must be a shader input
    0:18(6): error: no matching function for call to `length(error)';
candidates are:
    0:18(6): error:    float length(float)
    0:18(6): error:    float length(vec2)
    0:18(6): error:    float length(vec3)
    0:18(6): error:    float length(vec4)
    0:18(6): error:    double length(double)
    0:18(6): error:    double length(dvec2)
    0:18(6): error:    double length(dvec3)
    0:18(6): error:    double length(dvec4)
    0:18(6): error: operands to relational operators must be scalar and numeric
    0:18(6): error: if-statement condition must be scalar boolean

Changing the shader to use:

    in  vec3 icolor;
    in  vec2 iuv;

fixes the problem. This seems to be related to
https://patchwork.freedesktop.org/patch/15298/, but the input variable check is
too strict. It should work with an input block as well, which is for instance
used by the G-Truc samples:
https://github.com/g-truc/ogl-samples/blob/655559499c23b9566ac432cc2af33cde6646271c/data/gl-400/fbo-multisample-interpolate.frag

Code in question works fine on AMD desktop drivers.

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