[Bug 76862] New: clamp with bounds inside [0, 1] generates slow code

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=76862

          Priority: medium
            Bug ID: 76862
          Assignee: idr at freedesktop.org
           Summary: clamp with bounds inside [0, 1] generates slow code
        QA Contact: intel-3d-bugs at lists.freedesktop.org
          Severity: enhancement
    Classification: Unclassified
                OS: All
          Reporter: idr at freedesktop.org
          Hardware: Other
            Status: NEW
           Version: git
         Component: glsl-compiler
           Product: Mesa

Code sequences like

     a = clamp(b, 0, .5)
     c = clamp(d, .1, 1);

generates both instructions.  However, each of these could be implemented with
a single instruction with a SAT modifier.  The first example above should be

    MAX_SAT   a, b, .5;

and the second should be

    MIN_SAT   c, d, .1;

The requirements for this optimiation are that the lower bound be zero and the
upper bound less than 1, or the lower bound greater than zero and the upper
bound equal to 1.

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