On 07/31/2013 02:17 PM, Paul Berry wrote:
According to GLSL, indexing into an array or matrix with an
out-of-range constant results in a compile error. However, indexing
with an out-of-range value that isn't constant merely results in
undefined results.
Since optimization passes (e.g. loop unrolling) can convert
non-constant array indices into constant array indices, it's possible
that ir_set_program_inouts will encounter a constant array index that
is out of range; if this happens, just mark the whole array as used.
---
src/glsl/ir_set_program_inouts.cpp | 31 ++++++++++++++++++++++++++-----
1 file changed, 26 insertions(+), 5 deletions(-)
diff --git a/src/glsl/ir_set_program_inouts.cpp
b/src/glsl/ir_set_program_inouts.cpp
index b4588a7..018342b 100644
--- a/src/glsl/ir_set_program_inouts.cpp
+++ b/src/glsl/ir_set_program_inouts.cpp
@@ -171,13 +171,34 @@
ir_set_program_inouts_visitor::try_mark_partial_variable(ir_variable *var,
if (!index_as_constant)
return false;
- int width = 1;
- if (type->is_array() && type->fields.array->is_matrix()) {
- width = type->fields.array->matrix_columns;
+ unsigned elem_width;
+ unsigned num_elems;
+ if (type->is_array()) {
+ num_elems = type->length;
+ if (type->fields.array->is_matrix())
+ elem_width = type->fields.array->matrix_columns;
+ else
+ elem_width = 1;
+ } else {
+ num_elems = type->matrix_columns;
+ elem_width = 1;
}
- mark(this->prog, var, index_as_constant->value.u[0] * width, width,
- this->shader_type == GL_FRAGMENT_SHADER);
+ if (index_as_constant->value.u[0] >= num_elems) {
+ /* Constant index outside the bounds of the matrix/array. This could
+ * arise as a result of constant folding of a legal GLSL program.
+ *
+ * Even though the spec says that indexing outside the bounds of a
+ * matrix/array results in undefined behaviour, we don't want to pass
+ * out-of-range values to mark() (since this could result in slots that
+ * don't exist being marked as used), so just let the caller mark the
+ * whole variable as used.
+ */
At least for the loop-unroll case, I seem to recall other compilers
generating a link-time error. I may be misremembering. I'd like to
have a follow-on patch (eventually) that either emits a warning or an
error here. I think the trick will be making the message useful. :(
+ return false;
+ }
+
+ mark(this->prog, var, index_as_constant->value.u[0] * elem_width,
+ elem_width, this->shader_type == GL_FRAGMENT_SHADER);
return true;
}
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