I'll add a piglit test for this.  I cut-and-paste that code into a shader (and did 's/[[]ERROR]: [0-9]*: //'), and I get:

Failed to compile vertex shader bad.vert: 0:30(1): error: syntax error, unexpected $end

(In reply to Ian Romanick from comment #1)
> I'll add a piglit test for this.  I cut-and-paste that code into a shader
> (and did 's/[[]ERROR]: [0-9]*: //'), and I get:

And 's/ \\$//'

> Failed to compile vertex shader bad.vert: 0:30(1): error: syntax error,
> unexpected $end

(In reply to Ian Romanick from comment #1)
> I'll add a piglit test for this.  I cut-and-paste that code into a shader
> (and did 's/[[]ERROR]: [0-9]*: //'), and I get:
> 
> Failed to compile vertex shader bad.vert: 0:30(1): error: syntax error,
> unexpected $end

Which I now realized is due to the shader being empty after preprocessing.  With the test case below, I cannot reproduce this issue.  I tried a couple similar things.  Eero: Can you provide a small case that reproduces this?

#version 400 core
#define SV_30    1
#define highp
#define mediump
#define lowp
#define TYPE_vertex
#define DO_EMISSIVE_AND_AMBIENT 0
#define NUM_COLORS 64
#define NUM_LIGHTS 16
#ifdef TYPE_fragment
#if !DO_EMISSIVE_AND_AMBIENT
#define DO_LOOP_ITERATION(i)
#define DO_2_LOOP_ITERATIONS(i)
#define DO_4_LOOP_ITERATIONS(i)
#define DO_6_LOOP_ITERATIONS(i)
#define DO_8_LOOP_ITERATIONS(i)
#define DO_16_LOOP_ITERATIONS(i)
#endif
#if !DO_EMISSIVE_AND_AMBIENT
#endif
#if DO_EMISSIVE_AND_AMBIENT
#else
#endif
#endif
#ifdef TYPE_vertex
#if !DO_EMISSIVE_AND_AMBIENT
#endif
#if !DO_EMISSIVE_AND_AMBIENT
#endif
#endif

void main()
{
}

That shader is in internal shader-db as "4.shader_test".

(All GfxBench shaders are a bit weird, the same shader contains both vertex & fragment shader code and it uses define & ifdef so that pre-processor extracts correct code for give shader stage for the compiler.)

Here's a minimal reproducing test case:

#version 110

#ifdef THING_1
#define THING_2(x) \
                if (x)
#endif

void main()
{
    gl_Position = vec4(0);
}

Proposed patch:

https://patchwork.freedesktop.org/patch/246834/

Fixed by:

commit b9fe8ff23dcfe4956be1eac4de0838d4a3720315
Author: Timothy Arceri <tarceri@itsqueeze.com>
Date:   Sat Sep 1 23:57:38 2018 +1000

    glsl: fixer lexer for unreachable defines
    
    If we have something like:
    
       #ifdef NOT_DEFINED
       #define A_MACRO(x) \
            if (x)
       #endif
    
    The # on the #define is not skipped but the define itself is so
    this then gets recognised as #if.
    
    Until 28a3731e3f this didn't happen because we ended up in
    <HASH>{NONSPACE} where BEGIN INITIAL was called stopping the
    problem from happening.
    
    This change makes sure we never call RETURN_TOKEN_NEVER_SKIP for
    if/else/endif when processing a define.
    
    Cc: Ian Romanick <idr@freedesktop.org>
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107772
    Tested-By: Eero Tamminen <eero.t.tamminen@intel.com>
    Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

Verified. GfxBench ALU2 test works fine now like the other tests.