[Mesa-dev] [Bug 97804] Later precision statement isn't overriding earlier one

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97804

            Bug ID: 97804
           Summary: Later precision statement isn't overriding earlier one
           Product: Mesa
           Version: git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: glsl-compiler
          Assignee: mesa-dev at lists.freedesktop.org
          Reporter: eero.t.tamminen at intel.com
        QA Contact: intel-3d-bugs at lists.freedesktop.org

Created attachment 126514
  --> https://bugs.freedesktop.org/attachment.cgi?id=126514&action=edit
Glmark2 shader triggering the bug

GLES 3.2 spec:
https://www.khronos.org/registry/gles/specs/3.2/GLSL_ES_Specification_3.20.pdf

States following in "4.7.4 Default Precision Qualifiers":
--------------------------------------------
Non-precision qualified declarations will use the precision qualifier specified
in the most recent precision statement that is still in scope. The precision
statement has the same scoping rules as variable declarations.
...
*Multiple precision statements for the same basic type can appear inside the
same scope, with later statements overriding earlier statements within that
scope.*
...
"
All languages except for the fragment language have the following predeclared
globally scoped default precision statements:
   precision highp float;
...
The fragment language has no default precision qualifier for floating point
types. Hence for float, floating point vector and matrix variable declarations,
either the declaration must include a precision qualifier or the default float
precision must have been previously declared.
--------------------------------------------

Check for latter was added with bug 60737, but precision overriding doesn't
seem to work.

Attached Glmark2 shader test fails to Mesa bug 97532.  Vertex shader float
uniform defaults to highp, and same should happen in fragment shader, however,
that happens only if the first precision statement in shader is removed, as
only then it will pass the linker check.  I.e.  precision overriding doesn't
work.

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