| Summary: | GLSL: opt_vectorize goes wrong on texture lookups | ||
|---|---|---|---|
| Product: | Mesa | Reporter: | Aras Pranckevicius <aras> |
| Component: | glsl-compiler | Assignee: | Matt Turner <mattst88> |
| Status: | RESOLVED FIXED | QA Contact: | Intel 3D Bugs Mailing List <intel-3d-bugs> |
| Severity: | normal | ||
| Priority: | medium | CC: | idr |
| Version: | git | ||
| Hardware: | All | ||
| OS: | All | ||
| Whiteboard: | |||
| i915 platform: | i915 features: | ||
(In reply to comment #0) > I can make this bug go away by stopping vectorizing on texture samples, i.e. > adding something like this to opt_vectorize.cpp: > > > /** > * Upon entering an ir_texture, remove the current assignment from > * further consideration. Vectorizing multiple texture lookups into one > * is wrong. > */ > ir_visitor_status > ir_vectorize_visitor::visit_enter(ir_texture *) > { > this->current_assignment = NULL; > return visit_continue_with_parent; > } Cool. Can you send that as a patch to mesa-dev? |
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Looks like opt_vectorize is too eager on texture lookups. For example, a shader like this (which does a color correction effect by looking up R,G,B channels into a ramp texture): uniform sampler2D _MainTex; uniform sampler2D _RampTex; varying vec2 varUV; void main() { vec4 orig = texture2D (_MainTex, varUV); float rr = texture2D (_RampTex, orig.xx).x; float gg = texture2D (_RampTex, orig.yy).y; float bb = texture2D (_RampTex, orig.zz).z; vec4 color = vec4 (rr, gg, bb, orig.w); gl_FragData[0] = color; } These 3 lookups effectively get vectorized into something like a: t.xyz = texture2DProj (_RampTex, t.xyz).xyz; I can make this bug go away by stopping vectorizing on texture samples, i.e. adding something like this to opt_vectorize.cpp: /** * Upon entering an ir_texture, remove the current assignment from * further consideration. Vectorizing multiple texture lookups into one * is wrong. */ ir_visitor_status ir_vectorize_visitor::visit_enter(ir_texture *) { this->current_assignment = NULL; return visit_continue_with_parent; }