On 7 November 2011 11:12, Ian Romanick <<a href="mailto:idr@freedesktop.org">idr@freedesktop.org</a>> wrote: <div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"> From: Ian Romanick <<a href="mailto:ian.d.romanick@intel.com">ian.d.romanick@intel.com</a>> This prevents other code from seeing a swizzle of the 16th component of a vector, for example. NOTE: This is a candidate for the 7.11 branch. Signed-off-by: Ian Romanick <<a href="mailto:ian.d.romanick@intel.com">ian.d.romanick@intel.com</a>> Bugzilla: <a href="https://bugs.freedesktop.org/show_bug.cgi?id=42517" target="_blank">https://bugs.freedesktop.org/show_bug.cgi?id=42517</a> --- src/glsl/lower_vec_index_to_swizzle.cpp | 17 +++++++++++++++-- 1 files changed, 15 insertions(+), 2 deletions(-) diff --git a/src/glsl/lower_vec_index_to_swizzle.cpp b/src/glsl/lower_vec_index_to_swizzle.cpp index c7630c2..ebc0833 100644 --- a/src/glsl/lower_vec_index_to_swizzle.cpp +++ b/src/glsl/lower_vec_index_to_swizzle.cpp @@ -33,6 +33,7 @@ #include "ir_visitor.h" #include "ir_optimization.h" #include "glsl_types.h" +#include "main/macros.h" /** * Visitor class for replacing expressions with ir_constant values. @@ -76,8 +77,20 @@ ir_vec_index_to_swizzle_visitor::convert_vec_index_to_swizzle(ir_rvalue *ir) void *ctx = ralloc_parent(ir); this->progress = true; - return new(ctx) ir_swizzle(deref->array, - ir_constant->value.i[0], 0, 0, 0, 1); + + /* Page 40 of the GLSL 1.20 spec says: + * + * "When indexing with non-constant expressions, behavior is undefined + * if the index is negative, or greater than or equal to the size of + * the vector." + * + * The ir_swizzle constructor gets angry if the index is negative or too + * large. For simplicity sake, just clamp the index to [0, size-1]. + */ + const int i = MIN2(MAX2(ir_constant->value.i[0], 0), + (deref->array->type->vector_elements - 1)); + + return new(ctx) ir_swizzle(deref->array, i, 0, 0, 0, 1); } ir_visitor_status -- 1.7.6.4 </blockquote><div> Reviewed-by: Paul Berry <<a href="mailto:stereotype441@gmail.com">stereotype441@gmail.com</a>> </div></div>